tag:theconversation.com,2011:/id/topics/dinosaur-extinction-7953/articlesDinosaur extinction – The Conversation2024-01-24T19:01:54Ztag:theconversation.com,2011:article/2214822024-01-24T19:01:54Z2024-01-24T19:01:54ZA newly identified ‘Hell chicken’ species suggests dinosaurs weren’t sliding toward extinction before the fateful asteroid hit<figure><img src="https://images.theconversation.com/files/570405/original/file-20240119-25-cv46uw.jpg?ixlib=rb-1.1.0&rect=386%2C718%2C3592%2C2613&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Birdlike dinosaur *Eoneophron infernalis* was about the size of an adult human. </span> <span class="attribution"><span class="source">Zubin Erik Dutta</span></span></figcaption></figure><p>Were dinosaurs already on their way out when an asteroid hit Earth 66 million years ago, ending the <a href="https://www.britannica.com/science/Cretaceous-Period">Cretaceous</a>, the geologic period that started about 145 million years ago? It’s a question that has vexed <a href="https://scholar.google.com/citations?user=Yqc3u-gAAAAJ&hl=en&oi=ao">paleontologists</a> <a href="https://scholar.google.com/citations?user=RCWbDQQAAAAJ&hl=en&oi=ao">like us</a> for more than 40 years.</p>
<p>In the late 1970s, debate began about whether dinosaurs were at their peak or in decline before their big extinction. Scientists at that time noted that while dinosaur diversity seemed to have increased in the geologic stage that spanned 83.6 million to 71.2 million years ago, the <a href="https://doi.org/10.1126/science.232.4750.629">number of species on the scene</a> seemed to decrease during the last few million years of the Cretaceous. Some researchers have interpreted this pattern to mean that the <a href="https://theconversation.com/more-bad-news-for-dinosaurs-chicxulub-meteorite-impact-triggered-global-volcanic-eruptions-on-the-ocean-floor-91053">asteroid that struck the Gulf of Mexico</a> was <a href="https://doi.org/10.1073/pnas.1521478113">simply the final blow</a> <a href="https://doi.org/10.1038/s41467-021-23754-0">for an already vulnerable group of animals</a>.</p>
<p>However, others have argued that what looks like a decrease in <a href="https://doi.org/10.1038/307360a0">the diversity of dinosaurs</a> may be an artifact of <a href="https://doi.org/10.1098/rsos.201195">how hard it is to accurately count them</a>. Fossil formations might <a href="https://doi.org/10.1073/pnas.0606028103">preserve different dinosaurs more or less often</a> based on factors like their favored environment and how easily their bodies fossilized there. The accessibility of various outcrops could influence what kinds of fossils researchers have so far found. These biases are a problem because fossils are what paleontologists must rely on to conclusively answer how healthy dinosaur populations were when the asteroid hit.</p>
<p>At that crucial moment, what was really happening to dinosaur diversity? Discovery, identification and description of new dinosaurs provide vital clues. This is where <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0294901">our work</a> comes in. Close examination of what we’d thought was a juvenile specimen of an already known species of dinosaur from this time period revealed that it was actually part of an adult from a completely new species. </p>
<p>Our work focusing on the life stage of our specimen demonstrates that dinosaur diversity may not have been declining before the asteroid hit, but rather that there are more species from this time period yet to be discovered – potentially even through reclassification of fossils already in museum collections.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/570889/original/file-20240123-21-ep8hu1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="hand on one of three long fossil bones with a ruler" src="https://images.theconversation.com/files/570889/original/file-20240123-21-ep8hu1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/570889/original/file-20240123-21-ep8hu1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570889/original/file-20240123-21-ep8hu1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570889/original/file-20240123-21-ep8hu1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570889/original/file-20240123-21-ep8hu1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570889/original/file-20240123-21-ep8hu1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570889/original/file-20240123-21-ep8hu1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Kyle Atkins-Weltman holds the femur of the new dinosaur as it was received, with the other fossils in the background.</span>
<span class="attribution"><span class="source">Kyle Atkins-Weltman</span></span>
</figcaption>
</figure>
<h2>Clues inside the bones of a birdlike dinosaur</h2>
<p>Our new study focused on four hindlimb bones – a <a href="https://www.britannica.com/science/femur">femur</a>, a <a href="https://www.britannica.com/science/tibia">tibia</a> and two <a href="https://www.britannica.com/science/metatarsal">metatarsals</a>. They were unearthed in South Dakota, in rocks of the <a href="https://ucmp.berkeley.edu/science/parks/hellcreek.php">Hell Creek Formation</a>, and date to the final 2 million years of the Cretaceous.</p>
<p>When we first examined the bones, we identified them as belonging to a family of dinosaurs known as the caenagnathids – a group of birdlike dinosaurs that had toothless beaks, long legs and short tails. <a href="https://doi.org/10.1080/08912963.2020.1726908">Direct</a> <a href="https://doi.org/10.1038/nature08965">fossil</a> <a href="https://doi.org/10.1038/35003103">and</a> <a href="https://www.infona.pl/resource/bwmeta1.element.agro-article-a7940458-6921-49de-8963-52892bc56dc8">inferred</a> <a href="https://doi.org/10.1371/journal.pone.0092022">evidence</a> <a href="https://experts.umn.edu/en/publications/section-1-systematics-fossil-record-and-biogeography-chapter-1-pe">indicates</a> <a href="https://experts.umn.edu/en/publications/chapter-2-the-fossil-record-of-mesozoic-and-paleocene-pennaraptor">these dinosaurs</a> were <a href="https://doi.org/10.1038/31635">covered in complex feathers</a>, much <a href="https://www.vertpala.ac.cn/EN/Y2000/V38/I04/241">like modern birds</a>.</p>
<p>The only known species of <a href="https://doi.org/10.1371/journal.pone.0092022">caenagnathid from this time and region</a> was <em>Anzu</em>, sometimes called the “<a href="https://www.theguardian.com/science/2014/mar/19/dinosaur-chicken-hell-anzu-wyliei">chicken from Hell</a>.” Covered in feathers and sporting wings and a toothless beak, <em>Anzu</em> was between roughly 450 and 750 pounds (200 and 340 kilograms). Despite its fearsome nickname, though, its diet is a matter of debate. It was likely an omnivore, eating both plant material and small animals.</p>
<p>Because our specimen was significantly smaller than <em>Anzu</em>, we simply assumed it was a juvenile. We chalked up the anatomical differences we noticed to its juvenile status and smaller size – and figured the animal would have changed had it continued to grow. <em>Anzu</em> specimens are rare, and no definite juveniles have been published in the scientific literature, so we were excited to potentially learn more about how it grew and changed throughout its lifetime <a href="https://doi.org/10.1525/california/9780520273528.003.0004">by looking inside its bones</a>.</p>
<p>Just like with a tree’s rings, <a href="https://doi.org/10.1126/sciadv.aax6250">bone records rings called lines of arrested growth</a>. Each annual line represents part of a year when the animal’s growth slowed. They would tell us how old this animal was, and how fast or slow it was growing.</p>
<p>We cut through the middle of three of the bones so that we could microscopically examine the internal anatomy of the cross-sections. What we saw <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0294901">completely uprooted our initial assumptions</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/570996/original/file-20240123-17-53v1e0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="cross-section 'slice' of yellowish fossilized bone with growth lines like the rings of a tree" src="https://images.theconversation.com/files/570996/original/file-20240123-17-53v1e0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/570996/original/file-20240123-17-53v1e0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=455&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570996/original/file-20240123-17-53v1e0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=455&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570996/original/file-20240123-17-53v1e0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=455&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570996/original/file-20240123-17-53v1e0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=572&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570996/original/file-20240123-17-53v1e0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=572&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570996/original/file-20240123-17-53v1e0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=572&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Teal markers point to lines of arrested growth on the cross-section of fossilized bone. Toward the outside of the bone, the lines are much closer together, reflecting less growth per year. Researchers counted exactly six lines, meaning this animal was between 6 and 7 years old when it died.</span>
<span class="attribution"><span class="source">Holly Woodward</span></span>
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<p>In a juvenile, we would expect lines of arrested growth in the bone to be widely spaced, indicating rapid growth, with even spacing between the lines from the inside to the outside surface of the bone. Here, we saw that the later lines were spaced progressively closer together, indicating that this animal’s growth had slowed and it was nearly at its adult size.</p>
<p>This was no juvenile. Instead, it was an adult of an entirely new species, which we dubbed <em>Eoneophron infernalis</em>. The name means “Pharaoh’s dawn chicken from Hell,” referencing the nickname of its larger cousin <em>Anzu</em>. Traits unique to this species include ankle bones fused to the tibia, and a well-developed ridge on one of its foot bones. These weren’t features a young <em>Anzu</em> would outgrow, but rather unique aspects of the smaller <em>Eoneophron</em>.</p>
<h2>Expanding the caenagnathid family tree</h2>
<p>With this new evidence, we started making thorough comparisons with other members of the family to determine where <em>Eoneophron infernalis</em> fit within the group.</p>
<p>It also inspired us to reexamine other bones previously believed to be <em>Anzu</em>, as we now knew that more caenagnathid dinosaurs lived in western North America during that time. One specimen, a partial foot bone smaller than our new specimen, appeared distinct from both <em>Anzu</em> and <em>Eoneophron</em>. Where once there was one “chicken from Hell,” now there were two, and evidence for a third: one large (<em>Anzu</em>), weighing as much as a grizzly bear, one medium (<em>Eoneophron</em>), humanlike in weight, and one small and yet unnamed, close in size to a German shepherd.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/570405/original/file-20240119-25-cv46uw.jpg?ixlib=rb-1.1.0&rect=386%2C718%2C3592%2C2613&q=45&auto=format&w=1000&fit=clip"><img alt="wooded scene with three different sizes of bird-like dinosaur" src="https://images.theconversation.com/files/570405/original/file-20240119-25-cv46uw.jpg?ixlib=rb-1.1.0&rect=386%2C718%2C3592%2C2613&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/570405/original/file-20240119-25-cv46uw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=447&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570405/original/file-20240119-25-cv46uw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=447&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570405/original/file-20240119-25-cv46uw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=447&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570405/original/file-20240119-25-cv46uw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=561&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570405/original/file-20240119-25-cv46uw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=561&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570405/original/file-20240119-25-cv46uw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=561&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Eoneophron infernalis</em> and the smaller unnamed species now join the larger <em>Anzu</em> as late-Cretaceous caenagnathid dinosaurs from the Hell Creek region.</span>
<span class="attribution"><span class="source">Zubin Erik Dutta</span></span>
</figcaption>
</figure>
<p>Comparing Hell Creek with older fossil formations <a href="https://doi.org/10.1080/08912963.2020.1726908">such as the famous Dinosaur Park Formation of Alberta</a> that preserves dinosaurs that <a href="https://doi.org/10.1038/s41598-022-19896-w">lived between 76.5 million and 74.4 million years ago</a>, we find not only the same number of caenagnathid species, but also the same size classes. There, we have <em>Caenagnathus</em>, comparable to <em>Anzu</em>, <em>Chirostenotes</em>, comparable to <em>Eoneophron</em>, and <em>Citipes</em>, comparable to the third species we found evidence for. These parallels in both species count and relative sizes offer compelling evidence that caenagnathids remained stable throughout the last part of the Cretaceous. </p>
<p>Our new discovery suggests that this dinosaur group was not declining in diversity at the very end of the Cretaceous. These fossils show that there are still new species to be discovered, and support the idea that at least part of the pattern of decreasing diversity is the result of sampling and preservation biases.</p>
<p>Did large dinosaurs go extinct the way a Hemingway character quipped he went broke: “<a href="https://cardinalinstitute.com/gradually-then-suddenly/">gradually, then suddenly</a>”? While there are plenty of questions still outstanding in this extinction debate, <em>Eoneophron</em> adds evidence that caenagnathids were doing quite well for themselves before the asteroid ruined everything.</p>
<p><em>This article has been updated to correct the full name in English of the new species.</em></p><img src="https://counter.theconversation.com/content/221482/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Rather than a juvenile of a known species, several fossilized bones represent a new species – and shed light on the question of whether dinosaurs were already in decline before disaster struck.Kyle Atkins-Weltman, Ph.D. Student in Paleoecology, Oklahoma State UniversityEric Snively, Associate Professor of Anatomy and Cell Biology, Oklahoma State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2058662023-06-04T07:47:14Z2023-06-04T07:47:14ZWhat are meteorites? I visit and study the craters they’ve left across our planet<figure><img src="https://images.theconversation.com/files/528816/original/file-20230529-17-32pv8c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Impact cratering, caused by meteorites colliding with planetary surfaces, is one of the most fundamental cosmic processes.</span> <span class="attribution"><span class="source">Eshma/Shutterstock</span></span></figcaption></figure><p>Tens of thousands of <a href="https://spaceplace.nasa.gov/asteroid/en/">asteroids</a> – that we know of – are roaming our solar system. These are building blocks made up of metal, silicates, and ice left over from the beginning of time when the <a href="https://theconversation.com/curious-kids-how-are-planets-created-200454">planets</a> (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune) and their moons were assembling. </p>
<p>For the most part, the asteroids quietly orbit the Sun – but sometimes they collide with each other or the planets and their moons. An asteroid hitting a planetary surface is called a meteorite. When a meteorite moves at a hyper-speed, between 10km and 70km per second, the collision releases an enormous wave of energy and leaves something in its place on the planetary surface.</p>
<p>These meteorite or impact craters appear as scars. Some planets are more pockmarked with craters than others: <a href="https://www.google.com/maps/space/moon/@-17.1912213,44.6295626,11521099m/data=!3m1!1e3?entry=ttu">the Moon is covered</a> with thousands but the Earth has <a href="https://www.sciencedirect.com/science/article/pii/S0012825222001969">only 200 confirmed meteorite craters</a>. There are several reasons for this. First, meteorites slow down or even burn out in our atmosphere before they can reach the surface. Second, 70% of Earth is covered with water – we can only see craters on land. Earth also has <a href="https://theconversation.com/plate-tectonics-new-findings-fill-out-the-50-year-old-theory-that-explains-earths-landmasses-55424">tectonic plates</a>, which shift and constantly renew the surface.</p>
<p>I am a geoscientist who studies impact craters. I have visited 10 of Earth’s confirmed crater sites, in places as diverse as the Amazon jungle, the Arctic polar circle, central Europe, and South Africa. I’ve even studied lunar samples collected by the Apollo missions.</p>
<p>Impact cratering is one of the most fundamental cosmic processes. It is responsible for the growth of planetary bodies through accretion (the accumulation of mass). For example, the Moon was created as a result of a collision between the young Earth and a smaller planet, Theia. </p>
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<figcaption><span class="caption">The moon started with a literal ‘bang’</span></figcaption>
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<p>It has been proven that the <a href="https://theconversation.com/how-the-dinosaurs-went-extinct-asteroid-collision-triggered-potentially-deadly-volcanic-eruptions-112134">extinction of dinosaurs</a> was caused by a massive impact event. Thus, studying impact craters can broaden our understanding of the Earth’s evolution and life, as well its possible future.</p>
<h2>Studying impactites</h2>
<p>I moved to the Free State province in South Africa after defending my doctoral thesis at Austria’s University of Vienna. The closest, most interesting geological site was the Vredefort impact crater. It is <a href="https://earthobservatory.nasa.gov/images/92689/vredefort-crater">the world’s oldest and largest known impact structure</a>, dating back some 2 billion years and spanning between 180km and 300km in diameter.</p>
<p>With fellow researchers, I visited Vredefort several times a year to collect a variety of data. <a href="https://scholar.google.com/citations?hl=ru&user=KIoAMa0AAAAJ&view_op=list_works&sortby=pubdate">Impact cratering research</a> helps me to combine two of my big passions - metamorphic petrology (how rocks can be transformed from one type into another) and the deformation of minerals (how they change their shape and structure under stress). </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/what-a-moroccan-crater-reveals-about-a-rare-double-whammy-from-the-skies-61406">What a Moroccan crater reveals about a rare double whammy from the skies</a>
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<p>So, what happens when an impact crater is formed? A combination of intense heat (reaching thousands of degrees Celsius) and pressure (millions of <a href="https://education.nationalgeographic.org/resource/atmospheric-pressure/">atmospheres</a>) at the moment the meteorite hits the planetary surface. The meteorite is destroyed and part of the target evaporates. </p>
<p>That spot of collision is what’s known as an impact crater; the ground around and below it is full of rocks called <a href="https://www.lpi.usra.edu/publications/books/CB-954/chapter5.pdf">impactites</a>. These cannot be found anywhere else: impactites are not formed by any natural processes, only by meteorite impacts. Unique deformation features form in the minerals that were already on the planet’s surface. </p>
<figure class="align-center ">
<img alt="An aerial view of a rugged, rocky landscape interspersed with patches of green" src="https://images.theconversation.com/files/528822/original/file-20230529-9150-asis0o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/528822/original/file-20230529-9150-asis0o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/528822/original/file-20230529-9150-asis0o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/528822/original/file-20230529-9150-asis0o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/528822/original/file-20230529-9150-asis0o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/528822/original/file-20230529-9150-asis0o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/528822/original/file-20230529-9150-asis0o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A satellite image of the Vredefort impact crater in South Africa’s Free State province.</span>
<span class="attribution"><span class="source">Planet Observer/Universal Images Group via Getty Images</span></span>
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</figure>
<p>Sometimes, new minerals are found – examples include <a href="https://link.springer.com/referenceworkentry/10.1007/0-387-30720-6_25">coesite and stishovite</a>, which are high-pressure modifications of quartz, and <a href="https://pubchem.ncbi.nlm.nih.gov/compound/Reidite">reidite</a> - a high-pressure modification of zircon. Another one is impact diamond, called <a href="https://www.nature.com/articles/ncomms6447">lonsdaleite</a>.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/glass-beads-in-lunar-soil-reveal-ancient-asteroid-bombardments-on-the-moon-and-earth-191342">Glass beads in lunar soil reveal ancient asteroid bombardments on the Moon and Earth</a>
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<h2>Cutting-edge technology</h2>
<p>Studying impactites isn’t, of course, as easy as looking at them with the naked eye or even putting them under a conventional microscope. A technology called <a href="https://www.sciencedirect.com/topics/physics-and-astronomy/transmission-electron-microscopy">transmission electron microscopy</a> (TEM) is driving the latest research in this field. It has been used for a few decades but, in recent years, there have been big improvements in its quality and precision.</p>
<p>TEM is a way to observe the micro- and nano-structures of impactites at an unbelievably high resolution. Using thin, specially prepared samples, features as small as a few nanometers in size – that’s about 1/10,000th of the diameter of a human hair – can be characterised in terms of their composition, shape, crystalline structure and relationship with the surroundings. Individual molecules and their patterns in crystals can be recognised and imaged. We can even identify what mineral we are looking at by analysing the arrangement of molecules.</p>
<p>This technology is opening the door to an entirely new world of impactite study. Our small-scale analyses will reveal ever more of the Universe’s huge secrets.</p><img src="https://counter.theconversation.com/content/205866/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elizaveta Kovaleva receives funding from the National Research Foundation of South Africa, the Alexander Von Humboldt Foundation of Germany, and in the past received funding from the Russian Science Foundation. </span></em></p>Studying impact craters can broaden our understanding of the Earth’s evolution and life, as well as its possible future.Elizaveta Kovaleva, Lecturer, University of the Western CapeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1810232022-04-27T12:48:12Z2022-04-27T12:48:12ZDoes this dinosaur ‘graveyard’ reveal their final day on Earth? An expert explores the evidence<p>Buried in the rocks in North Dakota lies evidence of the exact day the dinosaurs were obliterated from the planet, some 66 million years ago. That’s the claim of palaeontologist Robert DePalma and colleagues, whose work was captured by the BBC in its recent landmark documentary <a href="https://www.bbc.co.uk/programmes/m0016djt">Dinosaurs: The Final Day with David Attenborough</a>.</p>
<p>For the last ten years, DePalma has focused his work on a <a href="https://en.wikipedia.org/wiki/Tanis_(fossil_site)">fossil rich site</a> – which he has named “Tanis” – in North Dakota’s Hell Creek Formation. And since 2019, he and his colleagues have put forward some very strong claims about what Tanis tells us about the end of the Cretaceous period.</p>
<p>DePalma believes that Tanis is a mass graveyard of creatures killed during the asteroid strike. </p>
<p>There is no doubt that an asteroid led to the <a href="https://www.science.org/doi/full/10.1126/science.aay5055">mass extinction</a> of non-avian dinosaurs – and at least 50% of other species – 66 million years ago. But there has been some controversy around DePalma’s claim that the site documents the very day that the asteroid struck – and reveals direct evidence of the very last dinosaurs on Earth.</p>
<p>So, let’s take a look at what we know about this most important time in our planet’s history – and what remains uncertain.</p>
<h2>The huge asteroid collision</h2>
<p>When the asteroid impact theory was <a href="https://en.wikipedia.org/wiki/Alvarez_hypothesis">first proposed in 1980</a>, there was no crater. The only evidence was two sites with substantial enrichment of iridium – an element that arrives on the Earth’s surface from outer space – in the rocks exactly at the level of the end of the Cretaceous. </p>
<p>Now there are hundreds of places worldwide showing the iridium spike, at what is known as the K-Pg (Cretaceous-Paleogene) boundary, a geological signature in the sediment.</p>
<p>And then in 1991 came the huge breakthrough - the <a href="https://theconversation.com/how-does-an-invisible-underwater-crater-prove-an-asteroid-killed-the-dinosaurs-57711">Chicxulub crater</a> was found in what is now the Yucatán Peninsula in southern Mexico. </p>
<p>At 180km (110 miles) wide, and 20km (12 miles) deep, the crater shows that a huge 10km (six mile) wide asteroid crashed into the sea. Its force was so great, that it unleashed huge tsunami waves, as well as massive amounts of rock debris and <a href="https://theconversation.com/scientists-have-found-dust-from-the-asteroid-that-wiped-out-the-dinosaurs-inside-the-crater-it-left-156232">dust containing iridium</a> into the atmosphere – and also triggered a <a href="https://theconversation.com/revealed-asteroid-that-killed-the-dinosaurs-boiled-earths-atmosphere-36606">powerful heat wave</a>.</p>
<p>Most experts agree that all life within around 1,700km (1,000 miles) of the collision would have been wiped out instantly. </p>
<p>But Tanis was more than 2,800km (or 1,800 miles) away. And up until now, there was no evidence of the very last dinosaurs. So, what’s the basis for DePalma’s groundbreaking revelation that Tanis finally provides the elusive evidence of the dinosaurs’ last day?</p>
<h2>Asteroid evidence at Tanis</h2>
<p>There is little doubt that the Tanis site lies close to the end of the Cretaceous Period, because DePalma has identified the iridium layer immediately above the fossil bed, which places it at the K-Pg boundary.</p>
<p>He has also presented some compelling pieces of evidence that the site marks the exact day the asteroid struck.</p>
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Read more:
<a href="https://theconversation.com/dinosaur-killing-asteroid-struck-at-worst-angle-to-cause-maximum-damage-new-research-139394">Dinosaur-killing asteroid struck at worst angle to cause maximum damage – new research</a>
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<p>First, there are the ancient channels in the sedimentary rocks at Tanis – these are evidence of the huge standing water (or “seiche”) waves which engulfed Tanis. At that time North America was divided by a great seaway that passed close to the Tanis site: the seiche waves would have run up the creeks, and out again, several times, mixing fresh and sea waters to create the waves.</p>
<p>The ground-borne shock waves from the asteriod impact – which caused the devastating water surges – could readily travel through the Earth’s crust from the impact site to Tanis. </p>
<p>When the asteroid crashed into Earth, tiny ejector spherules, glassy beads about 1mm wide, were formed from melted molten rock – and were able to travel up to around 3,200km (2,000 miles) through the atmosphere because they were so light. </p>
<p>Astonishingly, DePalma found these glassy spherules at the site, and also in the gills of sturgeon fossils which occupied the Tanis streams. He believes the spherules were produced by the Chicxulub impact because of their shared chemistry, with some even encapsulating “fragments of the asteroid” itself. If this is true, their occurrence at Tanis would indeed confirm that they mark the actual day of impact, because the spherules would have fallen to the ground within hours of the impact.</p>
<h2>Tanis fossil findings</h2>
<p>From decades of study of the rocks and fossils at <a href="https://en.wikipedia.org/wiki/Hell_Creek_Formation">Hell Creek Formation</a>, we know that Tanis was a warm and wet forest environment, with a thriving ecosystem full of dinosaurs, pterosaurs (flying reptiles), turtles and early mammals. Although they are yet to be described in detail, DePalma and colleagues reveal some incredible new fossils of animals – and he believes they could well have died on the day of the impact itself, due to their location in the doomed Tanis sandbank. </p>
<p>First, there’s an exceptionally <a href="https://www.theguardian.com/science/2022/apr/07/fossil-dinosaur-killed-asteroid-strike-thescelosaurus-north-dakota-extinction?fr=operanews">preserved leg</a> of the herbivorous dinosaur <em>Thescelosaurus</em>, which shows not only the bones, but also skin and other soft tissues. </p>
<p>But that’s not all. There is a pterosaur baby, just about to hatch from its egg – and, some incredibly well preserved <em>Triceratops</em> skin, which is an extremely unusual find.</p>
<p>Even more astonishingly, there is a turtle impaled by a stick, which DePalma believes could be evidence of a tragic death in the turbulent seiche waves set off by the impact.</p>
<p>DePalma’s final claim is that the impact, and final day, <a href="https://www.nature.com/articles/s41598-021-03232-9">occurred in May</a>, based on microscopic and geochemical analysis of growth rings in the fin spines of the fossil sturgeon. The bones show seasonal banding – where bone grows rapidly when food is abundant and slowly when conditions are poorer, so often summers are shown by a wide pale band and winters by a narrow dark band. The last banding cycle in the sturgeon confirms it died in May. And a <a href="https://www.nature.com/articles/s41586-022-04446-1">further study</a> this year has confirmed this.</p>
<h2>So, why the uncertainty?</h2>
<p>There is no doubt that DePalma’s claims <a href="https://www.science.org/doi/epdf/10.1126/science.364.6435.10">have been controversial</a> since they were first presented to the world in 2019 – probably because the announcement was in the <a href="https://www.newyorker.com/magazine/2019/04/08/the-day-the-dinosaurs-died">New Yorker magazine</a> rather than a peer-reviewed journal.</p>
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Read more:
<a href="https://theconversation.com/fish-bones-and-water-lilies-help-pin-down-the-month-the-dinosaurs-died-175459">Fish bones and water lilies help pin down the month the dinosaurs died</a>
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<p>But the findings about seiche waves were then published in an <a href="https://www.pnas.org/doi/abs/10.1073/pnas.1817407116">academic paper </a> only a month later, and most geologists were convinced.</p>
<p>It is true that the fossils, which were revealed for the first time in the BBC documentary – along with the evidence that the glass spherules at Tanis are linked to the Chicxulub impact – have yet to be published in scientific journals, where they would be subject to peer review.</p>
<p>But, experience shows that most of what DePalma has revealed in the past has been backed up subsequently by peer-reviewed papers. </p>
<p>Over the past two years I worked as one of the independent scientific consultants to the BBC, verifying the claims, as they made the documentary. Both I and my colleagues, and many other experts, are satisfied that the Tanis site probably does reveal the very last day of the non-avian dinosaurs.</p>
<p>And of course, as we all know, the impact of the asteriod went far beyond that one day. It led to a freezing dark planet, on a global scale, lasting for days or maybe weeks – and, from this mass extinction worldwide, the age of the mammals emerged.</p><img src="https://counter.theconversation.com/content/181023/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael J. Benton receives funding from Natural Environment Research Council, Leverhulme Trust, European Research Council.</span></em></p>A recent BBC documentary examined fossils thought to have been made when an asteroid wiped out the dinosaurs.Michael J. Benton, Professor of Vertebrate Palaeontology, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1753172022-03-28T05:44:25Z2022-03-28T05:44:25ZHidden away in a museum, we found the skull of a rare armoured dinosaur that roamed Queensland 105 million years ago<figure><img src="https://images.theconversation.com/files/450544/original/file-20220307-126102-1xbnuoz.jpg?ixlib=rb-1.1.0&rect=21%2C21%2C3591%2C2465&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>You might think all important dinosaur “discoveries” are made as soon as fossils are collected in the field – that palaeontologists instantly know the significance of what they’ve found.</p>
<p>This is often true. But sometimes, and maybe more often than you’d think, fossils will be stored in museum collections for years before the right researchers come along to “rediscover” them. This was the case for one Australian ankylosaur skull, which we’ve <a href="https://www.frontiersin.org/articles/10.3389/feart.2022.803505/full">published about</a> today in the journal Frontiers in Earth Sciences.</p>
<p>Originally discovered in 2005 near the regional Queensland town of Boulia, the specimen remained at the South Australian Museum until we enquired about the museum’s dinosaur collection.</p>
<p>Ankylosaurs, the so-called “armoured” dinosaurs, are a group of dinosaurs that lived from the Early Jurassic to the Late Cretaceous – roughly 196 to 66 million years ago.</p>
<p>Compared to other dinosaurs, such as the <a href="https://theconversation.com/introducing-australotitan-australias-largest-dinosaur-yet-spanned-the-length-of-2-buses-162177">long-necked sauropods</a> and smaller herbivorous <a href="https://www.tandfonline.com/doi/full/10.1080/02724634.2019.1564757">ornithopods</a>, ankylosaur remains are rarely found in Australia and the broader southern hemisphere. So you can imagine our excitement when we “rediscovered” Australia’s second ankylosaur skull. </p>
<p>An analysis of the skull bones and teeth suggests it belongs to the genus <a href="https://peerj.com/articles/1475/"><em>Kunbarrasaurus</em></a>, which also contains the first Australian ankylosaur skull.</p>
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Read more:
<a href="https://theconversation.com/introducing-australotitan-australias-largest-dinosaur-yet-spanned-the-length-of-2-buses-162177">Introducing Australotitan: Australia's largest dinosaur yet spanned the length of 2 buses</a>
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<h2>What were ankylosaurs like?</h2>
<p>Ankylosaurs were medium-to-giant herbivorous dinosaurs (anywhere between 200-5,000kg) that walked on four legs and were covered in armoured plates or spikes. Some are recognisable by tail clubs, such as the five-tonne <em>Ankylosaurus magniventris</em> from North America.</p>
<p>Of the 75 <a href="https://paleobiodb.org/">recognised</a> ankylosaur species, only five are from the southern hemisphere. Several small and incomplete fossils are spattered across the ancient Gondwana supercontinent – which is now dispersed and broken up into Australia, India (which back then was in the southern hemisphere), Africa, Antarctica and South America. </p>
<p>These fossils offer tantalising hints of what was once a widespread ankylosaur presence in these regions. The five Gondwanan ankylosaur species are <em>Kunbarrasaurus ieversi</em> and <em>Minmi paravertebra</em> from Australia, <em>Antarctopelta oliveroi</em> from Antarctica, <em>Spicomellus afer</em> from Africa, and <em>Stegorous elengassen</em> from Chile. </p>
<h2>A dinosaur from Boulia</h2>
<p>The bones of the ankylosaur from Boulia were found encased in a large, hard rock called a <a href="https://geokansas.ku.edu/concretion">concretion</a>. Concretions often form around organic matter, and likely helped the initial preservation of the fossil. When it was discovered, all that was visible was a series of rock chunks that could have easily been overlooked. </p>
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<img alt="" src="https://images.theconversation.com/files/448774/original/file-20220228-95421-1w371cu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/448774/original/file-20220228-95421-1w371cu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/448774/original/file-20220228-95421-1w371cu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/448774/original/file-20220228-95421-1w371cu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/448774/original/file-20220228-95421-1w371cu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/448774/original/file-20220228-95421-1w371cu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/448774/original/file-20220228-95421-1w371cu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The Boulia ankylosaur was excavated from the Warra station in 2005. (Block in the bottom left contains ankylosaur limb bones)</span>
<span class="attribution"><span class="source">Benjamin Kear (Uppsala University)</span></span>
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<p>The collected fossils include limbs, vertebrae, many armoured plates and, excitingly, a partial skull. Along with several skull bones, the skull also includes the impressions of many teeth from the upper jaw. </p>
<p>The entire skull block was scanned at the Australian Synchrotron in Melbourne. The synchrotron shoots x-rays at the specimen, generating a series of images that can be processed to reveal the bones in 3D (as seen below). </p>
<iframe src="https://une.pedestal3d.com/r/K-iBggKkmP?sidebar=closed" width="100%" height="600px"></iframe>
<p>This technique is often used for fossils that may otherwise get damaged or lose important information if physically removed from the rock.</p>
<p>We analysed the scans and discovered the bones are those of the roof of the mouth (or the palate). We also found several teeth “floating” within the block.</p>
<h2>Placing southern ankylosaurs in the family tree</h2>
<p>Identifying this new ankylosaur as <em>Kunbarrasaurus</em> suggests this particular dinosaur was potentially more widespread in Queensland than previously thought, and may have existed for more than five million years. But what do ankylosaurs from Australia, and Gondwana more generally, tell us about the group’s evolution as a whole?</p>
<p>As it stands, the vast majority of ankylosaurs are from either North America, Europe, or Asia. And most are from the late Cretaceous (100 to 66 million years ago). However our study suggests a separate and possibly earlier diversity of ankylosaurs in the south, a theory which is supported by recent discoveries from <a href="https://www.abc.net.au/news/2021-12-02/dinosaur-has-resemblance-to-aztec-weapon/100667992">South America</a> and <a href="https://www.nhm.ac.uk/discover/news/2021/september/new-species-of-dinosaur-had-armour-unlike-anything-seen-before.html">Africa</a>.</p>
<p>The southern radiation of ankylosaurs includes the species from Australia, Chile and Antarctica, all of which together form the group called <a href="https://www.nature.com/articles/d41586-021-03572-6">Parankylosauria</a>. </p>
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<img alt="" src="https://images.theconversation.com/files/448777/original/file-20220228-95421-1p3j8px.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/448777/original/file-20220228-95421-1p3j8px.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/448777/original/file-20220228-95421-1p3j8px.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/448777/original/file-20220228-95421-1p3j8px.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/448777/original/file-20220228-95421-1p3j8px.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/448777/original/file-20220228-95421-1p3j8px.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/448777/original/file-20220228-95421-1p3j8px.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A reconstruction of <em>Kunbarrrasaurus ieversi</em> from Richmond, Queensland.</span>
<span class="attribution"><span class="source">Australian Geographic</span></span>
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<h2>The importance of the Boulia ankylosaur</h2>
<p>Because the fossil block was scanned with x-rays and reconstructed in 3D, we were able to explore aspects of the ankylosaur’s airways, or “choanae”. These were not well preserved in the first and only other known <em>Kunbarrasaurus</em> skull.</p>
<p>Typically ankylosaur choanae are long, located close to the front of the snout and can have multiple openings within the palate. Coupled with complex nasal passages, these features point to the group generally having a keen sense of smell.</p>
<p>However, in the Boulia ankylosaur there is only one opening on each side, and they are located towards the back of the palate. This suggests <em>Kunbarrasaurus</em> did not have the complex nasal system seen in ankylosaurs such as <em><a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0150845">Pawpawsaurus campbelli</a></em> and <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0207381"><em>Euplocephalus tutus</em></a>. As such, it may have had a reduced sense of smell compared to most of its northern counterparts. </p>
<p>There is still a lot we don’t know about ankylosaur evolution, especially the Gondwanan species. Perhaps more of these discoveries await us in museum troves.</p>
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Read more:
<a href="https://theconversation.com/dinosaurs-were-already-in-decline-before-the-asteroid-wiped-them-out-new-research-163624">Dinosaurs were already in decline before the asteroid wiped them out – new research</a>
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<p class="fine-print"><em><span>Nicolas Campione receives funding from Australian Research Council. </span></em></p><p class="fine-print"><em><span>Phil Bell received funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Timothy Frauenfelder does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>An analysis of the skull suggests the ankylosaur may have had a poorer sense of smell than its counterparts in the northern hemisphere.Timothy Frauenfelder, PhD Candidate in Palaeontology, University of New EnglandNicolas Campione, Senior lecturer, University of New EnglandPhil Bell, Palaeontologist, Earth Science Faculty, University of New EnglandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1754592022-01-25T10:53:21Z2022-01-25T10:53:21ZFish bones and water lilies help pin down the month the dinosaurs died<figure><img src="https://images.theconversation.com/files/442223/original/file-20220124-25-18u4jou.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C5962%2C4138&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/3d-rendering-tyrannosaurus-rex-near-extinction-471399755">Herschel Hoffmeyer/Shutterstock</a></span></figcaption></figure><p>The dinosaurs were killed by a meteorite impact on the Earth some 66 million years ago in what has become known as the <a href="https://www.britannica.com/science/K-T-extinction">Cretaceous-Paleogene extinction event</a>. At what time of the year this occurred has long <a href="https://www.quora.com/How-do-scientists-know-that-the-K-T-extinction-event-occurred-in-June-or-July">generated debate</a> among palaeontology enthusiasts.</p>
<p>A recent study published in <a href="https://www.nature.com/articles/s41598-021-03232-9">Nature</a> builds on earlier evidence to suggest the dinosaurs probably met their demise in June. The fact that researchers have been able to pinpoint the timing of an event that happened millions of years ago is a remarkable feat of science – but more on that later.</p>
<p>The latest evidence comes from a site called <a href="https://en.wikipedia.org/wiki/Tanis_(fossil_site)">Tanis</a>, located in the Hell Creek Formation in North Dakota. Tanis is one of several geological locations around the world where scientists have observed the Cretaceous-Paleogene boundary in the succession of sediments.</p>
<p>Tanis has yielded wonderful fossils of dinosaurs, early mammals, fish, plants and other things. Many of these fossils are exceptionally well preserved, with some showing remains of soft tissues, such as skin, as well as bones, which can offer valuable scientific insights.</p>
<p>The Tanis site was first identified in 2008 and has been the focus of fieldwork by palaeontologist Robert DePalma since then. In a <a href="https://www.pnas.org/content/116/17/8190">2019 paper</a>, DePalma and his colleagues argued that Tanis captured the moment of the asteroid’s impact, due to three factors. </p>
<p>The first was the presence of dinosaur fossils occurring in the Cretaceous sediments right up to the Cretaceous-Paleogene boundary, and exactly at the boundary at the time of impact. </p>
<p>The second was a layer of melt spherules: tiny glass balls that cooled in flight from molten rock. When the asteroid struck Earth in the region of what is now the Yucatán Peninsula in Mexico, it spread debris and melt spherules for thousands of kilometres.</p>
<figure class="align-center ">
<img alt="A 3D rendering of an asteroid hitting Earth." src="https://images.theconversation.com/files/442330/original/file-20220124-17-xal3qn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/442330/original/file-20220124-17-xal3qn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/442330/original/file-20220124-17-xal3qn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/442330/original/file-20220124-17-xal3qn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/442330/original/file-20220124-17-xal3qn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/442330/original/file-20220124-17-xal3qn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/442330/original/file-20220124-17-xal3qn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Cretaceous-Paleogene extinction event happened 66 million years ago when an asteroid hit Earth.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/3d-renderingasteroid-hitting-earth-creating-huge-1776867431">ImageBank4u/Shutterstock</a></span>
</figcaption>
</figure>
<p>The third was evidence of seiche waves (see-saw-like standing waves) in deep channels. The Tanis site is well inland today, but at the end of the Cretaceous period it was located on the coast of the western interior seaway that divided North America at that time, with sea levels <a href="https://news.mongabay.com/2008/03/cretaceous-sea-levels-were-550-feet-higher-than-today/">some 200 metres higher</a> than they are today. The site was estuarine, which means fresh and salt waters were mingling. </p>
<p>The seiche waves were generated by the distant impact in Mexico, which set off <a href="https://www.pnas.org/content/116/17/8190">seismic waves</a> that shook the Earth and caused water to flow in and out of the river channels at a fast rate, estimated as beginning one hour after the impact.</p>
<p>As well as melt spherules within the fossil-bearing rocks, the researchers found abundant spherules in the gill skeletons of some of the fish they examined. We can imagine that as they floundered in the violently oscillating waters of the river channel, they could have swallowed melt spherules coming from above.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-some-species-thrive-after-catastrophe-rules-for-making-the-most-of-an-apocalypse-140889">Why some species thrive after catastrophe – rules for making the most of an apocalypse</a>
</strong>
</em>
</p>
<hr>
<h2>Looking more closely at the fish</h2>
<p>In December 2021, DePalma and his colleagues published an important paper about the timing of the Cretaceous-Paleogene extinction event. In this <a href="https://www.nature.com/articles/s41598-021-03232-9">study</a>, they analysed some of the exceptionally well-preserved fish bones, looking at how the cycle of seasons, from summer to winter, were documented in the structure and chemistry of the bones.</p>
<p>By comparing living sturgeon to sturgeon fossils from Tanis, they found that in a fin spine, regular layering at a scale of millimetres shows the fish died when it was seven years old. The growth rings confirm the fish alternated between fresh waters in summer months and saline waters in winter. In this and other specimens analysed in the same study, the last growth increment matches the transition from spring to summer. </p>
<p>Taken together, this suggests the meteorite struck in May or June, being the cusp of spring and summer in the northern hemisphere. </p>
<figure class="align-center ">
<img alt="The Siberian sturgeon (Acipenser baerii)." src="https://images.theconversation.com/files/442237/original/file-20220124-27-wxkiig.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/442237/original/file-20220124-27-wxkiig.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=347&fit=crop&dpr=1 600w, https://images.theconversation.com/files/442237/original/file-20220124-27-wxkiig.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=347&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/442237/original/file-20220124-27-wxkiig.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=347&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/442237/original/file-20220124-27-wxkiig.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=437&fit=crop&dpr=1 754w, https://images.theconversation.com/files/442237/original/file-20220124-27-wxkiig.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=437&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/442237/original/file-20220124-27-wxkiig.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=437&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Scientists have been able to compare modern sturgeon to sturgeon from the Cretaceous period to study when they died.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/siberian-sturgeon-acipenser-baerii-aquarium-tank-1608297007">Arunee Rodloy/Shutterstock</a></span>
</figcaption>
</figure>
<p>Importantly, these findings confirm <a href="https://www.nature.com/articles/352420a0">earlier evidence</a> based on fossil plants, which suggested the extinction event took place in early June. </p>
<p>Palaeobotanist Jack Wolfe identified a location in Wyoming that showed the effect of the meteorite on a freshwater lake. At the point of impact, the lake froze, preserving fossil plants in exquisite detail.</p>
<p>By comparing the fossil plants to similar modern water lilies <em>Nuphar</em> and <em>Nelumbo</em>, he showed that the latest Cretaceous water lilies in the lake had been halted in their growth at a point in their trajectory of producing summer leaves, flowers and fruit which indicated freezing in early June.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/jurassic-world-can-we-really-resurrect-a-dinosaur-97383">Jurassic World: can we really resurrect a dinosaur?</a>
</strong>
</em>
</p>
<hr>
<p>Palaeontologists often say they would need a time machine to understand the details of past life, such as the month the dinosaurs died out. But here we see extraordinary conclusions can emerge from <a href="https://thamesandhudson.com/the-dinosaurs-rediscovered-9780500295533">careful analysis and rational comparison</a> with the modern day.</p><img src="https://counter.theconversation.com/content/175459/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael J. Benton does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A recent study provides additional evidence that the dinosaurs died in June.Michael J. Benton, Professor of Vertebrate Palaeontology, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1723902021-12-06T02:19:34Z2021-12-06T02:19:34ZCurious Kids: how did crocodiles survive the asteroid that killed the dinosaurs?<figure><img src="https://images.theconversation.com/files/434368/original/file-20211129-27-mkupzq.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C7678%2C5154&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Michael Lee</span>, <span class="license">Author provided</span></span></figcaption></figure><blockquote>
<p><strong>How did the crocodiles survive the asteroid that killed the dinosaurs? – Éamonn, age 5, Western Australia</strong></p>
</blockquote>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>Hi Éamonn! This is a great question, and one many scientists have asked. </p>
<p>There are two main reasons. First, crocodiles can live for a very long time without food. Second, they lived in places that were the least affected when the asteroid hit Earth. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/433380/original/file-20211123-15-cv830r.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/433380/original/file-20211123-15-cv830r.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/433380/original/file-20211123-15-cv830r.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=347&fit=crop&dpr=1 600w, https://images.theconversation.com/files/433380/original/file-20211123-15-cv830r.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=347&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/433380/original/file-20211123-15-cv830r.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=347&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/433380/original/file-20211123-15-cv830r.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=436&fit=crop&dpr=1 754w, https://images.theconversation.com/files/433380/original/file-20211123-15-cv830r.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=436&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/433380/original/file-20211123-15-cv830r.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=436&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A battle-scarred saltwater crocodile resting near the Daintree River in North Queensland.</span>
<span class="attribution"><span class="source">Michael Lee</span></span>
</figcaption>
</figure>
<h2>When the asteroid hit earth</h2>
<p>About <a href="https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_boundary">66 million years ago</a>, dinosaurs ruled Earth. But then a massive asteroid, more than 9 kilometres wide, slammed into the shallow sea near what is now Mexico.</p>
<p><a href="https://www.smithsonianmag.com/science-nature/fossil-site-captures-dinosaur-killing-impact-its-only-beginning-story-180971868/">The explosion</a> from this was so huge, it led to global earthquakes, tidal waves, bushfires and even poisonous rain. </p>
<p>Also, the asteroid hit at one of <a href="https://www.bbc.com/news/science-environment-39922998">the worst possible places</a>, where the rocks could easily be “exploded” (or vapourised). This threw up massive amounts of dust into the sky, blocking out the Sun for many months and sending Earth into a long, dark and freezing winter.</p>
<p>Without sunlight, the green plants died, followed by the plant-eating animals that ate them to survive, and the meat-eaters that ate the plant-eaters.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-effect-did-the-asteroid-that-wiped-out-the-dinosaurs-have-on-plants-and-trees-132386">Curious Kids: What effect did the asteroid that wiped out the dinosaurs have on plants and trees?</a>
</strong>
</em>
</p>
<hr>
<p>Scientists think <a href="https://theconversation.com/catastrophic-failure-of-earths-global-systems-led-to-the-extinction-of-the-dinosaurs-we-may-yet-go-the-same-way-114348">three-quarters of all the different kinds (species) of animals on Earth were wiped out</a> – including most dinosaurs.</p>
<p>But some managed to survive for a range of reasons.</p>
<p>One important group of dinosaurs <a href="https://www.smithsonianmag.com/science-nature/why-birds-survived-and-dinosaurs-went-extinct-after-asteroid-hit-earth-180975801/">sailed through</a>, helped by their ability to fly and find food in faraway places. Their feathers protected them from the cold, and their beaks let them eat buried seeds found near dead plants. </p>
<p>Amazingly, these dinosaur survivors are still with us today. We call them birds!</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-small-birds-evolved-from-giant-meat-eating-dinosaurs-28540">How small birds evolved from giant meat eating dinosaurs</a>
</strong>
</em>
</p>
<hr>
<h2>Crocodiles had some keys to survival</h2>
<p>Crocodiles were another group that famously survived the asteroid. Obviously they can’t fly, don’t have feathers, and don’t eat seeds! But they had other secrets to success.</p>
<p>Firstly, crocodile bodies use <a href="https://zooatlanta.org/how-do-crocodiles-stay-submerged-so-long/">very little energy</a>. They lie around a lot, breathe slowly and even have a very slow heartbeat. This is how they can hold their breath underwater for more than an hour. </p>
<p>It also means they can go without food for months, and sometimes more than a year. This would have been very helpful when food (such as other animals) became hard to find once the asteroid hit. </p>
<p>Dinosaurs, on the other hand, were <a href="https://theconversation.com/hot-fuss-is-warm-blooded-dinosaur-theory-right-or-wrong-8174">generally more active, which means they needed more energy</a> – especially meat-eaters like <em>Velociraptor</em>. Without food, they would have died quickly.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/434922/original/file-20211201-15-i7vd8m.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/434922/original/file-20211201-15-i7vd8m.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/434922/original/file-20211201-15-i7vd8m.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434922/original/file-20211201-15-i7vd8m.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434922/original/file-20211201-15-i7vd8m.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434922/original/file-20211201-15-i7vd8m.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434922/original/file-20211201-15-i7vd8m.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434922/original/file-20211201-15-i7vd8m.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Dinosaurs such as Velociraptor would have struggled to survive without much food after the asteroid hit. That is, if they survived in the first place.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Crocodiles also lived in places where losing <a href="https://en.wikipedia.org/wiki/Cretaceous%E2%80%93Paleogene_extinction_event">green plants</a> didn’t make a big difference. Think of a forest or a grassland (where many dinosaurs lived): if the plants there die, then all the animals that need them die too, including the meat-eaters which are left with no food.</p>
<p>But the crocodile survivors mostly lived in places like rivers, lakes and coasts. The animals living in these places don’t need green plants as much. Dead plants and animal material washes in from surrounding land, which is eaten by tiny creatures, which are then eaten by larger creatures including crocodiles.</p>
<p>So unlike dinosaurs living on the land, crocodiles in a river would not have starved as soon as the green plants died. </p>
<h2>Our mammalian ancestors also survived</h2>
<p>A similar reason helps explain why human beings’ ancestors also survived the asteroid impact. These were the small mammals that lived near the end of the age of dinosaurs, which eventually gave rise to all the different kinds of mammals around today (including humans).</p>
<p>They were mainly small, rat-like things that scurried about in the dead leaf litter <a href="https://news.umich.edu/study-suggests-ground-dwelling-mammals-survived-mass-extinction-66-million-years-ago">on the ground</a>, eating insects and worms. These tiny creatures relied not on living green plants, but on dead leaves and bark falling from the trees, or being blown and washed in from elsewhere.</p>
<p>So just like the crocodiles, our tiny ancestors survived the asteroid partly because they didn’t depend heavily on living plants. A good thing too: these lucky survival skills are the reason you and I are here today!</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/2W5hOJaFjxU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Humans have had a long history – 3.8 billion years in the making. This video shows how humans evolved from the first life.</span></figcaption>
</figure><img src="https://counter.theconversation.com/content/172390/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mike Lee receives research funding from The Australian Research Council and Flinders University.</span></em></p>Crocodiles can survive without food for a long time – even up to more than a year – because of how well they can save their energy.Mike Lee, Professor in Evolutionary Biology (jointly appointed with South Australian Museum), Flinders UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1636242021-06-30T13:31:25Z2021-06-30T13:31:25ZDinosaurs were already in decline before the asteroid wiped them out – new research<p>Some 66 million years ago, on the Yucatán peninsula in Mexico, a <a href="https://arxiv.org/abs/1403.6391">12 kilometre-wide asteroid</a> crashes to Earth. The impact causes an explosion whose magnitude is hard to imagine today – several billion times more powerful than the atomic bomb dropped on Hiroshima.</p>
<p>Most of the animals on the American continent are killed immediately. The impact also triggers worldwide tsunamis. Tons and tons of dust are ejected into the atmosphere, plunging the planet into darkness. This “nuclear winter” causes the extinction of many plant and animal species.</p>
<p>Among the latter, the most emblematic: the dinosaurs. But how were the dinosaurs faring before this cataclysm? This is the question we try to answer in our new study, the results of which have just been published in the scientific journal <a href="https://doi.org/10.1038/s41467-021-23754-0"><em>Nature Communications</em></a>.</p>
<p>We were interested in six families of dinosaurs, the most representative and the most diversified of the 40 million years that preceded the arrival of the asteroid.</p>
<p>Three of these families were carnivorous: the Tyrannosauridae, the Dromaeosauridae (including the famous velociraptors, made famous by the <em>Jurassic Park</em> movies) and the Troodontidae (small dinosaurs similar to birds). </p>
<p>The other three were herbivores: the Ceratopsidae (represented in particular by the Triceratops), the Hadrosauridae (the richest of all the families in terms of diversity) and the Ankylosauridae (represented in particular by the ankylosaur, a dinosaur covered in bony armour with a club-like tail).</p>
<p>We knew that all these families had survived until the end of the Cretaceous marked by the fall of the asteroid. Our goal was to determine at what rate these families diversified – formed new species – or became extinct.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/408816/original/file-20210629-18-ci9req.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/408816/original/file-20210629-18-ci9req.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/408816/original/file-20210629-18-ci9req.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=315&fit=crop&dpr=1 600w, https://images.theconversation.com/files/408816/original/file-20210629-18-ci9req.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=315&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/408816/original/file-20210629-18-ci9req.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=315&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/408816/original/file-20210629-18-ci9req.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=396&fit=crop&dpr=1 754w, https://images.theconversation.com/files/408816/original/file-20210629-18-ci9req.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=396&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/408816/original/file-20210629-18-ci9req.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=396&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Possible appearance of an Ankylosaurus based on Carpenter 2004 skeletal reconstruction and fossil photographs.</span>
<span class="attribution"><a class="source" href="https://fr.wikipedia.org/wiki/Ankylosaurus#/media/Fichier:Ankylosaurus_dinosaur.png">Mariana Ruiz Villarreal LadyofHats/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>For five years, we compiled all the known information on these families in order to try to work out how many of them there were on Earth at a particular time, and which species were in each group. In palaeontology, each fossil is given a unique number for the sake of traceability, which allows us to follow it through the scientific literature over time.</p>
<p>The work was tedious – we inventoried most of the known fossils for these six families, which represented more than 1,600 individuals from around 250 species. It’s not easy to properly categorise each of the species and date them correctly: one researcher might have given a record a certain date and species, and then another might reexamine it and make a different analysis. In these cases, we had to make our own calls – if we had too many doubts, we eliminated the fossil from the study.</p>
<p>Once each fossil was properly categorised, we used a statistical model to estimate the number of species that evolved over time for each family. We were thus able to trace the species that appeared and those that disappeared between 160 and 66 million years ago and estimate, again for each family, the rates of speciation – the evolution of new species – and extinction over time.</p>
<p>To estimate these rates, we had to take several confounding factors into account. The fossil record is biased: it is uneven in time and space, and some types of dinosaur simply do not fossilise as well as others. This is a well-known problem in palaeontology when estimating the dynamics of past diversity.</p>
<p>Sophisticated models can account for uneven preservation over time and between species. In doing so, the fossil record becomes more reliable for estimating the number of species at any given time. But it is important to be cautious, because we are talking about estimates, and these estimates may change if we find more fossils, for example, or new analytical models.</p>
<h2>A steep decline</h2>
<p>Our results show that the number of species was in steep decline from 10 million years before the asteroid strike until the dinosaurs were wiped out. This decline is particularly interesting because it is worldwide, and affects both carnivorous groups such as tyrannosaurs, and herbivorous groups such as triceratops.</p>
<p>Some species declined sharply, like the ankylosaurs and ceratopsians, and only one family out of the six – the troodontids – shows a very small decline, which took place in the last five million years of dinosaurs’ existence.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/409123/original/file-20210630-13-1ds3ugw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/409123/original/file-20210630-13-1ds3ugw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/409123/original/file-20210630-13-1ds3ugw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=349&fit=crop&dpr=1 600w, https://images.theconversation.com/files/409123/original/file-20210630-13-1ds3ugw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=349&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/409123/original/file-20210630-13-1ds3ugw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=349&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/409123/original/file-20210630-13-1ds3ugw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=438&fit=crop&dpr=1 754w, https://images.theconversation.com/files/409123/original/file-20210630-13-1ds3ugw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=438&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/409123/original/file-20210630-13-1ds3ugw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=438&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">a) Dynamics of speciation (blue) and extinction (red) rates through time for the six dinosaur families. b) Diversification rates over time.</span>
<span class="attribution"><span class="source">Fabien Contamine</span></span>
</figcaption>
</figure>
<p>What could have caused this strong decline? One theory is climate change: at that time, the Earth underwent a period of global cooling of 7 to 8°C.</p>
<p>We know that dinosaurs need a warm climate for their metabolism to function properly. As we often hear, they were not ectothermic (cold-blooded) animals like crocodiles or lizards, nor endothermic (warm-blooded), like mammals or birds. They were mesotherms, a metabolic system between reptiles and mammals and needed a warm climate to maintain their temperature and thus perform basic biological functions. This temperature decrease must have had a strong impact on them.</p>
<p>It should be noted that we found a staggered decline between herbivores and carnivores: the grass-eaters declined slightly before the meat-eaters. It’s probable that the decline of herbivores caused the decline of carnivores. This is what we call cascade extinction.</p>
<h2>The knockout blow</h2>
<p>One big question remains: what would have happened if the asteroid had not crashed? Would dinosaurs have gone extinct anyway, due to the decline that had already begun, or could they have rebounded? It’s very difficult to say. Many palaeontologists believe that if the dinosaurs had survived, primates and therefore humans would never have appeared on Earth.</p>
<p>An important fact is that a possible rebound in diversity can be very heterogeneous and group-dependent, so that some groups would have survived and others not. Hadrosaurs, or “duck-billed” dinosaurs, for example, showed some form of resilience to the decline and might have bounced back after.</p>
<p>What we can say is that the ecosystems at the end of the Cretaceous period were under significant pressure due to climatic deterioration and major changes in vegetation, and that the asteroid dealt the final blow. This is often the case in the disappearance of species: first they are in decline and under pressure, then another event intervenes and finishes off a group that may have been on the verge of extinction anyway.</p><img src="https://counter.theconversation.com/content/163624/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Fabien Condamine ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.</span></em></p>If the asteroid caused the very sudden end of the dinosaurs, a new study shows that their decline had begun 10 million years earlier.Fabien Condamine, Chercheur au CNRS en Phylogénie et Evolution Moléculaire, Université de MontpellierLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1486232020-11-26T19:01:45Z2020-11-26T19:01:45ZCurious Kids: could dinosaurs evolve back into existence?<figure><img src="https://images.theconversation.com/files/371456/original/file-20201126-17-hqh45o.jpg?ixlib=rb-1.1.0&rect=336%2C176%2C5271%2C3354&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><blockquote>
<p><strong>Will there ever be dinosaurs again? — Anonymous</strong></p>
</blockquote>
<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>What an interesting question! Well, technically dinosaurs are still here in the <a href="https://www.science20.com/news_articles/evolving_by_shrinking_how_dinosaurs_became_birds-135809">form of birds</a>. Just like you’re a direct descendant of your grandparents, birds are the only remaining direct descendants of dinosaurs.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/371439/original/file-20201126-29-by0jzz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="_3D T. rex rendering_" src="https://images.theconversation.com/files/371439/original/file-20201126-29-by0jzz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/371439/original/file-20201126-29-by0jzz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371439/original/file-20201126-29-by0jzz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371439/original/file-20201126-29-by0jzz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371439/original/file-20201126-29-by0jzz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371439/original/file-20201126-29-by0jzz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371439/original/file-20201126-29-by0jzz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Tyrannosaurus rex</em> belonged to a dinosaur group called theropods.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>But I suppose what you’re really asking is whether dinosaurs like <em>Tyrannosaurus</em> or <em>Triceratops</em> could ever exist again. Although that would be fascinating, the answer is almost definitely no. </p>
<p>While there’s only one generation between you and your grandparents – that is, your parents – there are many millions of generations between today’s birds and their ancient dinosaurs ancestors.</p>
<p>This is why today’s birds look, sound and behave so differently to the prehistoric beasts that once roamed Earth.</p>
<h2>Animals evolve to change, but can’t choose how</h2>
<p>To understand this, we have to understand “evolution”. This is a process that explains how every living thing (<a href="https://www.nationalgeographic.com/magazine/2017/04/evolution-genetics-medicine-brain-technology-cyborg/">including humans</a>) <em>evolved</em> from past living things over millions, or even billions, of years. </p>
<p>Different animals evolve their own differences to help them survive in the world. For example, 66 million years ago, birds survived the <a href="https://www.nationalgeographic.com/science/prehistoric-world/dinosaur-extinction/">catastrophic event</a> that killed all other dinosaurs and marked the end of the Mesozoic era.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/371443/original/file-20201126-21-18xjx4p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="3D rendering of _T. rex_ facing off against a _Triceratops_ herd." src="https://images.theconversation.com/files/371443/original/file-20201126-21-18xjx4p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/371443/original/file-20201126-21-18xjx4p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371443/original/file-20201126-21-18xjx4p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371443/original/file-20201126-21-18xjx4p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371443/original/file-20201126-21-18xjx4p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=532&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371443/original/file-20201126-21-18xjx4p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=532&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371443/original/file-20201126-21-18xjx4p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=532&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fossils suggest face-offs between <em>T. rex</em> and <em>Triceratops</em> were common.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>After this, a blanket of ash wrapped around the world, cooling it and blocking out the sunlight plants need to survive. Plant-eating animals would have struggled to stay alive.</p>
<p>But birds did, perhaps because they were small even then. They likely ate seeds and insects and took shelter in small spaces. And being able to fly would have helped them explore far and wide for food and shelter. </p>
<p>That said, if the conditions that came after the dinosaur extinction event returned today, no modern animal would evolve back into a dinosaur. This is because animals today have a very different evolutionary past to dinosaurs. </p>
<p>They evolved to have features that help them survive in <em>today’s</em> world, rather than a prehistoric one. And these features limit the ways they can evolve in the future.</p>
<h2>Which came first, the chicken or the dinosaur?</h2>
<p>For an animal to be an actual “dinosaur”, it must belong to a group of animals known by scientists as Dinosauria. These all descended from a common ancestor shared by <em>Triceratops</em> and modern birds.</p>
<p>Other than birds, Dinosauria doesn’t include <em>any</em> living creature. So for a dinosaur to re-evolve in the future, it would have to come from a bird.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/XAzGC89n0S4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This animation helps paint a picture of how dinosaurs eventually evolved to become birds. (American Museum of Natural History/Youtube)</span></figcaption>
</figure>
<p>Dinosauria’s extinct members included sauropods, stegosaurs, ankylosaurs, ornithopods, ceratopsians and non-bird theropods. Modern birds evolved from a small group of theropods. However, since so much time has passed, this link is limited. </p>
<p>Specifically, birds have a very different collection of “genes”. These are the same built-in “rules” your parents passed down to you that decide, for example, what colour your eyes will be. </p>
<p>The more generations that pass between an ancestor and their descendant, the more different their genes will be.</p>
<h2>Even if it could happen, what would this take?</h2>
<p>Think of how much a bird would need to change to look like <em>Tyrannosaurus rex</em> or <em>Triceratops</em>. A lot.</p>
<p>Dinosaurs had long tails with bones all along them. Birds’ tails are stumpy and have been for more than 100 million years. It’s unlikely this would ever be reversed.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/371444/original/file-20201126-19-1677xfz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A falcon illustration with its skeleton inside visible." src="https://images.theconversation.com/files/371444/original/file-20201126-19-1677xfz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/371444/original/file-20201126-19-1677xfz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371444/original/file-20201126-19-1677xfz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371444/original/file-20201126-19-1677xfz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371444/original/file-20201126-19-1677xfz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371444/original/file-20201126-19-1677xfz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371444/original/file-20201126-19-1677xfz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">While some types of birds have long tail feathers, such as falcons (above) and pheasants, on the inside their tails are short.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Also, modern birds walk on their back legs only and (in most cases) have <a href="https://www.rspb.org.uk/birds-and-wildlife/natures-home-magazine/birds-and-wildlife-articles/how-do-birds-survive/birds-legs-and-feet/">four toes</a> and three “fingers” in their wings. </p>
<p>Compare that with <em>Triceratops</em>, which walked on all four limbs, had five fingers on its front feet (the inner three of which were weight-bearing) and four toes on its back feet.</p>
<p>It may not be <em>impossible</em> for birds to gain two more fingers to have five like <em>Triceratops</em>; some people with a condition called “polydactyly” have more than five fingers, but this is very rare.</p>
<p>There aren’t really any situations where an extra finger (or one less) would be necessary for a bird’s survival. Thus, there’s little to no chance birds will evolve to change in this way.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/371451/original/file-20201126-19-12qvdc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram showing different types of bird feet" src="https://images.theconversation.com/files/371451/original/file-20201126-19-12qvdc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/371451/original/file-20201126-19-12qvdc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=406&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371451/original/file-20201126-19-12qvdc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=406&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371451/original/file-20201126-19-12qvdc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=406&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371451/original/file-20201126-19-12qvdc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=510&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371451/original/file-20201126-19-12qvdc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=510&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371451/original/file-20201126-19-12qvdc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=510&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Most birds have four toes and three ‘fingers’ in their wings.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Even if birds did eventually start to walk on all four limbs (legs and wings), they wouldn’t move the same way a <em>Triceratops</em> did because the purpose of a bird’s wings is very different to that of a <em>Triceratops’s</em> legs.</p>
<h2>Dinosaurs are history</h2>
<p>We know from fossil discoveries that <em>Triceratops</em> and <em>Tyrannosaurus</em> had scaly skin covering most of their bodies. Most modern birds have scaly feet, but none are scaly all over.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/365432/original/file-20201026-13-rp2x88.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/365432/original/file-20201026-13-rp2x88.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=797&fit=crop&dpr=1 600w, https://images.theconversation.com/files/365432/original/file-20201026-13-rp2x88.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=797&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/365432/original/file-20201026-13-rp2x88.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=797&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/365432/original/file-20201026-13-rp2x88.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1002&fit=crop&dpr=1 754w, https://images.theconversation.com/files/365432/original/file-20201026-13-rp2x88.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1002&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/365432/original/file-20201026-13-rp2x88.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1002&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Although <em>Triceratops</em> had a ‘beak’ this was very different to a bird’s beak.</span>
<span class="attribution"><span class="source">Stephen Poropat/American Museum of Natural History</span></span>
</figcaption>
</figure>
<p>It’s hard to imagine what would force any bird to naturally replace its feathers with scales. Birds need feathers to fly, to save energy (by staying warm) and to put on special displays to attract mates.</p>
<p><em>Triceratops</em> did have a “beak” at the front of its mouth, but this evolved completely separately to the beaks of birds and had two extra bones — something no living animal has.</p>
<p>What’s more, behind its beak and jaws, <em>Triceratops</em> had rows of teeth. While some birds such as geese have spiky beaks. No bird in the past 66 million years has ever had teeth. </p>
<p>Considering these huge differences, it’s really unlikely birds will ever evolve to look more like their extinct dinosaur relatives. And no extinct dinosaur will ever come back to life either — except maybe in movies!</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/371470/original/file-20201126-21-x732j9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Geese with open mouths" src="https://images.theconversation.com/files/371470/original/file-20201126-21-x732j9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/371470/original/file-20201126-21-x732j9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371470/original/file-20201126-21-x732j9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371470/original/file-20201126-21-x732j9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371470/original/file-20201126-21-x732j9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371470/original/file-20201126-21-x732j9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371470/original/file-20201126-21-x732j9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Geese don’t have actual ‘teeth’, but they do have sharp points in their mouth to hold onto slippery things.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure><img src="https://counter.theconversation.com/content/148623/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephen Poropat does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>66 million years ago, birds survived the calamity that wiped out all prehistoric dinosaurs. But could birds once again evolve into their long lost ancestors?Stephen Poropat, Postdoctoral Researcher (Palaeontology), Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1408892020-07-20T13:27:45Z2020-07-20T13:27:45ZWhy some species thrive after catastrophe – rules for making the most of an apocalypse<figure><img src="https://images.theconversation.com/files/347993/original/file-20200716-37-2p3kw7.jpg?ixlib=rb-1.1.0&rect=0%2C438%2C1875%2C1294&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some species can do well in the face of extreme hardship.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-black-lava-green-fern-hawaii-42141481">George Burba/Shutterstock</a></span></figcaption></figure><p>Sixty-six million years ago, an <a href="https://science.sciencemag.org/content/327/5970/1214.abstract?casa_token=rse9tRx1m3EAAAAA:JA0HIX0oWHQsZAy80RHTxsa0jKO8UdvdPbaOLbbHXt5WxYzmu56TDok9A-ua3_bV8RhixQeV5olNZA">asteroid</a> struck the Earth. The world was plunged into darkness, killing the dinosaurs and over 90% of all species alive. Today, every living thing <a href="https://theconversation.com/profiles/nick-longrich-209117/dashboard#">descends from</a> the handful of surviving species. But not all survivors thrived. </p>
<p>Some groups – birds and placental mammals, butterflies and ants, sunflowers, grasses – diversified, taking advantage of the devastation. Some, like crocodiles and turtles, didn’t. And still others, like <a href="https://pubs.geoscienceworld.org/uwyo/rmg/article-abstract/24/special_paper_3/95/87858/Competitive-exclusion-and-taxonomic-displacement?redirectedFrom=PDF">multituberculate mammals</a> and <a href="https://ucmp.berkeley.edu/taxa/verts/archosaurs/choristodera.php">champsosaurus</a>, survived the asteroid but went extinct in the aftermath. </p>
<p>Why the difference? Surprisingly, what separated winners and losers wasn’t how hard extinction hit them. Rather, winners had qualities that made them adaptable and competitive after the extinction: they were fast-growing, mobile, cooperative and clever. </p>
<figure class="align-center ">
<img alt="Shark swimming." src="https://images.theconversation.com/files/343060/original/file-20200621-43196-1ggrr3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/343060/original/file-20200621-43196-1ggrr3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/343060/original/file-20200621-43196-1ggrr3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/343060/original/file-20200621-43196-1ggrr3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/343060/original/file-20200621-43196-1ggrr3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=473&fit=crop&dpr=1 754w, https://images.theconversation.com/files/343060/original/file-20200621-43196-1ggrr3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=473&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/343060/original/file-20200621-43196-1ggrr3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=473&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sharks, great survivors, weren’t great innovators.</span>
<span class="attribution"><span class="source">Wikipedia</span></span>
</figcaption>
</figure>
<p>Some groups were completely eliminated: dinosaurs, <a href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.2001663">pterosaurs</a>, <a href="https://www.sciencedirect.com/science/article/pii/S1342937X10001851">plesiosaurs</a> and ammonites. Obviously, they couldn’t take part in a recovery. But among survivors, the groups that won out tended to be those hit hard by extinction. </p>
<p><a href="https://www.researchgate.net/publication/230889811_Major_extinctions_of_land-dwelling_vertebrates_at_the_Cretaceous-Tertiary_boundary_eastern_Montana">Crocodilians, turtles</a> and <a href="https://www.sciencedirect.com/science/article/pii/S0960982218307632">sharks</a> were spared the brunt of the extinction, but aren’t especially diverse now. Meanwhile, groups that dominate today were devastated. Snakes and lizards saw <a href="https://www.pnas.org/content/109/52/21396">over 80% extinction</a>. Mammals were hit harder, suffering 90% extinction. Perhaps <a href="https://www.nature.com/articles/nature15697">three bird species survived</a>, suggesting extinction rates of 99.9% or more. </p>
<p>These groups were winners only in a relative sense – 99.9% extinction is terrible, but beats 100% extinction among tyrannosaurs. But while these animals initially suffered, they thrived when the dust literally settled. Four things gave them an edge.</p>
<h2>Metabolism</h2>
<p>First, winners had high metabolisms. Metabolic rate is how fast biological processes happen – meaning chemical reactions letting organisms grow, move, digest and reproduce. </p>
<figure class="align-center ">
<img alt="Field of sunflowers." src="https://images.theconversation.com/files/344391/original/file-20200628-104504-c6kbcc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/344391/original/file-20200628-104504-c6kbcc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=371&fit=crop&dpr=1 600w, https://images.theconversation.com/files/344391/original/file-20200628-104504-c6kbcc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=371&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/344391/original/file-20200628-104504-c6kbcc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=371&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/344391/original/file-20200628-104504-c6kbcc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=467&fit=crop&dpr=1 754w, https://images.theconversation.com/files/344391/original/file-20200628-104504-c6kbcc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=467&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/344391/original/file-20200628-104504-c6kbcc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=467&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Fast-growing sunflowers complete their lives in a summer.</span>
<span class="attribution"><span class="source">Wikipedia</span></span>
</figcaption>
</figure>
<p>Higher metabolism requires more food. This was initially a liability for warm-blooded birds and mammals during the impact winter, when plants couldn’t photosynthesise food. But afterwards, being able to eat, grow and breed fast let birds and mammals rapidly increase their numbers, compete effectively, and colonise new habitats. Fast-growing flowering plants, especially grasses, flourished at the expense of slower-growing species.</p>
<p>Even within these groups, we see high metabolism providing an edge. Among mammals, placental mammals, with their higher metabolisms, outcompeted <a href="https://www.redalyc.org/pdf/3699/369944274002.pdf">marsupials</a>. Passerines, the most diverse group of birds, also have <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0003261">higher metabolic rates</a> than other birds. </p>
<h2>Mobility</h2>
<p>Second, mobility promotes adaptability. Flight let birds, bats, butterflies and ants colonise new habitats, then diversify. Mammals, being highly mobile, quickly invade new habitats – think <a href="https://www.nationalgeographic.org/article/how-european-rabbits-took-over-australia/">rabbits in Australia</a>, or deer in New Zealand – in a way that turtles don’t. </p>
<figure class="align-center ">
<img alt="Two greylay geese flying above a landscape." src="https://images.theconversation.com/files/343059/original/file-20200621-43205-1lj3n6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/343059/original/file-20200621-43205-1lj3n6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/343059/original/file-20200621-43205-1lj3n6b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/343059/original/file-20200621-43205-1lj3n6b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/343059/original/file-20200621-43205-1lj3n6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=519&fit=crop&dpr=1 754w, https://images.theconversation.com/files/343059/original/file-20200621-43205-1lj3n6b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=519&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/343059/original/file-20200621-43205-1lj3n6b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=519&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Graylag geese in flight.</span>
<span class="attribution"><span class="source">Wikipedia</span></span>
</figcaption>
</figure>
<p>Flowering plants also evolved tricks – fruits, parachutes, burs, floating husks – to let wind, water or animals carry their seeds. It’s harder to displace competitors once they’re established, so being first into a new habitat provides a massive competitive advantage.</p>
<h2>Cooperation</h2>
<p>Third, winners tend to cooperate. Lions and wolves form prides and packs to take down prey and defend territory, elephants and zebras use herds for defence. Birds flock to find food and evade predators. </p>
<p>Ants and mound-building termites assemble vast family groups, outcompeting solitary insects. Birds, mammals and social insects also cooperate with relatives by feeding and <a href="https://theconversation.com/the-origin-and-evolution-of-love-131109">caring for offspring</a>, preserving their genes more efficiently.</p>
<figure class="align-center ">
<img alt="Group of ants holding a leaf." src="https://images.theconversation.com/files/347995/original/file-20200716-31-1cqcza5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/347995/original/file-20200716-31-1cqcza5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/347995/original/file-20200716-31-1cqcza5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/347995/original/file-20200716-31-1cqcza5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/347995/original/file-20200716-31-1cqcza5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/347995/original/file-20200716-31-1cqcza5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/347995/original/file-20200716-31-1cqcza5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ants cooperate.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/ant-action-standing-bridge-unity-teamconcept-1118781845">frank60/Shutterstock</a></span>
</figcaption>
</figure>
<p>Meanwhile, some species cooperate with other species. Leafcutter ants and termites form alliances with fungi, cultivating them in return for food. Flowering plants give away nectar and fruit to animals, which then pollinate flowers and spread their seeds. By cooperating, these species compete more effectively, so cooperative animals like ants, elephants and orcas tend to play bigger roles in the ecosystem than solitary ones like alligators and turtles.</p>
<h2>Intelligence</h2>
<p>But maybe the most remarkable trend is the rise of intelligence. Mammals and birds have the largest brains of any animals. The largest-brained mammals, the <a href="https://www.pnas.org/content/107/37/16216#F2">placentals</a>, have outcompeted marsupials and egg-laying monotremes. The most diverse birds, the passerines and parrots, are the <a href="https://pubmed.ncbi.nlm.nih.gov/15467290/">brainiest</a>. </p>
<p>Among insects, the social insects – ants, bees, termites – have complex behaviours that emerge from interactions of unintelligent individuals. This phenomenon is known as swarm intelligence, and not coincidentally, these insects dominated ecosystems after the asteroid winter. </p>
<figure class="align-center ">
<img alt="A dog wading through the sea on a rocky beach." src="https://images.theconversation.com/files/344395/original/file-20200628-104529-1uxc6cz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/344395/original/file-20200628-104529-1uxc6cz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=445&fit=crop&dpr=1 600w, https://images.theconversation.com/files/344395/original/file-20200628-104529-1uxc6cz.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=445&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/344395/original/file-20200628-104529-1uxc6cz.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=445&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/344395/original/file-20200628-104529-1uxc6cz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=560&fit=crop&dpr=1 754w, https://images.theconversation.com/files/344395/original/file-20200628-104529-1uxc6cz.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=560&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/344395/original/file-20200628-104529-1uxc6cz.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=560&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Polynesian dogs swim readily, and hunt crabs.</span>
<span class="attribution"><span class="source">Nick Longrich</span></span>
</figcaption>
</figure>
<p>But intelligence doesn’t just make animals more competitive. It accelerates adaptation, because the first step in changing your DNA is changing your mind. </p>
<p>For example, before mammals could <a href="https://evolution-outreach.biomedcentral.com/articles/10.1007/s12052-009-0135-2">evolve into whales</a>, they first had to learn to swim and fish, only afterwards could natural selection create flippers and sonar. Before horses could evolve, their omnivorous ancestors switched to a vegan diet, then, natural selection favoured tall-crowned teeth and complex guts to break down tough plants. Behaviour leads; genes follow.</p>
<figure class="align-center ">
<img alt="A humpback whale jumping out of the sea." src="https://images.theconversation.com/files/344396/original/file-20200628-104516-9uctpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/344396/original/file-20200628-104516-9uctpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/344396/original/file-20200628-104516-9uctpp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/344396/original/file-20200628-104516-9uctpp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/344396/original/file-20200628-104516-9uctpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/344396/original/file-20200628-104516-9uctpp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/344396/original/file-20200628-104516-9uctpp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Humpback whale.</span>
<span class="attribution"><span class="source">wikipedia</span></span>
</figcaption>
</figure>
<p>The greater an animal’s behavioural flexibility, the more tricks it can learn, and so the greater its adaptive potential. Animals don’t consciously decide their evolutionary futures. But they do choose what to eat, how to forage or where to live. </p>
<p>Whale ancestors didn’t dream of becoming dolphins, but they did dream of catching fish, and they imagined new fishing grounds. Being able to learn from yesterday, process information in dreams tonight, imagine different outcomes tomorrow – learning, memory processing, creativity – increase the number of potential evolutionary futures.</p>
<h2>No accident</h2>
<p>The continents were isolated in the early Cenozoic era just after the asteroid hit. Yet remarkably similar ecosystems dominated by mammals and birds evolved independently in South America, Africa, Australia and the Eurasian-North American supercontinent. That implies these groups’ dominance wasn’t an accident. </p>
<p>What’s striking is that these trends weren’t new – dinosaurs show similar patterns. Dinosaurs of the Cretaceous period had higher growth rates than their ancient Triassic ancestors. They were more mobile, some were fast runners, others – <a href="https://www.pnas.org/content/108/37/15253">birds</a> – flew.</p>
<p>The <a href="https://www.tandfonline.com/doi/pdf/10.1671/0272-4634(2000)020%5B0615%3AFEANTD%5D2.0.CO%3B2">brains of these</a> later dinosaurs were larger than earlier counterparts. <em>T. rex</em> was faster, <a href="https://www.tandfonline.com/doi/pdf/10.1671/0272-4634(2000)020%5B0615%3AFEANTD%5D2.0.CO%3B2">smarter</a> and had a faster <a href="https://www.nature.com/articles/nature02699">metabolism</a> than its forebears. Many – <a href="https://pubs.geoscienceworld.org/sepm/palaios/article-abstract/16/5/482/99813/The-Taphonomy-of-a-Centrosaurus-Ornithischia?redirectedFrom=fulltext">ceratopsians</a>, <a href="https://pubs.geoscienceworld.org/cjes/article-abstract/52/8/642/301101/Hadrosaurid-Edmontosaurus-bonebeds-from-the?redirectedFrom=fulltext">duckbills</a>, <a href="https://www.nature.com/articles/srep35782">avimimids</a> – show herding behaviours unknown from earlier dinosaurs.</p>
<p>During the asteroid winter, the rules briefly changed. Warm-blooded, fast-moving, cooperative, intelligent <a href="https://www.pnas.org/content/108/37/15253">birds</a>, mammals and dinosaurs fared poorly against turtles and alligators. Dinosaurs vanished. Afterwards, these trends reasserted themselves. </p>
<p>Evolution may offer us some lessons here. Be quick. Move to find new opportunities. Work with others. Try new things. But above all, change – adapt. </p>
<p>These are almost always good strategies, but especially when you’re down, trying for a comeback.</p><img src="https://counter.theconversation.com/content/140889/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas R. Longrich does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>When the dinosaurs went extinct, some species took over the world. Adaptability, not survivability, explains why.Nicholas R. Longrich, Senior Lecturer in Evolutionary Biology and Paleontology, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1308692020-04-02T21:35:38Z2020-04-02T21:35:38ZWhile we fixate on coronavirus, Earth is hurtling towards a catastrophe worse than the dinosaur extinction<figure><img src="https://images.theconversation.com/files/324623/original/file-20200401-23086-1fgcm8t.jpg?ixlib=rb-1.1.0&rect=2%2C2%2C1914%2C1195&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Pixabay </span></span></figcaption></figure><p>At several points in the history of our planet, increasing amounts of carbon dioxide in the atmosphere have caused extreme global warming, prompting <a href="https://www.sciencedaily.com/releases/2019/07/190708154057.htm">the majority of species</a> on Earth to die out.</p>
<p>In the past, these events were triggered by a huge <a href="https://www.scientificamerican.com/article/volcanoes-may-have-triggered-the-last-unexplained-mass-extinction/">volcanic eruption</a> or asteroid impact. Now, Earth is heading for another mass extinction – and human activity is to blame.</p>
<p>I am an Earth and Paleo-climate scientist and <a href="https://link.springer.com/search?dc.creator=%22Andrew%20Y.+Glikson%22">have researched</a> the relationships between asteroid impacts, volcanism, climate changes and mass extinctions of species.</p>
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Read more:
<a href="https://theconversation.com/heres-what-the-coronavirus-pandemic-can-teach-us-about-tackling-climate-change-134399">Here's what the coronavirus pandemic can teach us about tackling climate change</a>
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<p>My research suggests the current growth rate of carbon dioxide emissions is faster than those which triggered two previous mass extinctions, including the event that wiped out the dinosaurs. </p>
<p>The world’s gaze may be focused on COVID-19 right now. But the risks to nature from human-made global warming – and the imperative to act – remain clear.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=370&fit=crop&dpr=1 600w, https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=370&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=370&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=465&fit=crop&dpr=1 754w, https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=465&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/324785/original/file-20200402-23109-tia1km.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=465&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The current rate of CO2 emissions is a major event in the recorded history of Earth.</span>
<span class="attribution"><span class="source">EPA</span></span>
</figcaption>
</figure>
<h2>Past mass extinctions</h2>
<p>Many species can adapt to slow, or even moderate, environmental changes. But Earth’s history shows that extreme shifts in the climate can cause many species to <a href="https://www.abc.net.au/news/2019-11-13/what-is-a-mass-extinction-are-we-in-one-now/11699372">become extinct</a>. </p>
<p>For example, about 66 million years ago an asteroid hit Earth. The subsequent smashed rocks and widespread fires released massive amounts of carbon dioxide over <a href="https://www.pnas.org/content/99/12/7836">about 10,000 years</a>. Global temperatures soared, sea levels rose and oceans became acidic. About <a href="https://www.britannica.com/science/K-T-extinction">80% of species</a>, including the dinosaurs, were wiped out.</p>
<p>And about 55 million years ago, global temperatures spiked again, over <a href="https://www.nature.com/articles/ngeo578;%20https://www.nature.com/articles/ngeo1179;https://www.whoi.edu/fileserver.do?id=136084&pt=2&p=148709">100,000 years or so</a>. The cause of this event, known as the <a href="https://www.britannica.com/science/Paleocene-Eocene-Thermal-Maximum">Paleocene-Eocene Thermal Maximum</a>, is not entirely clear. One theory, known as the <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010RG000326">“methane burp” hypothesis</a>, posits that a massive volcanic eruption triggered the sudden release of methane from ocean sediments, making oceans more acidic and killing off many species. </p>
<p>So is life on Earth now headed for the same fate?</p>
<h2>Comparing greenhouse gas levels</h2>
<p>Before industrial times began at the end of the 18th century, carbon dioxide in the atmosphere sat at around <a href="https://data.giss.nasa.gov/modelforce/ghgases/">300 parts per million</a>. This means that for every one million molecules of gas in the atmosphere, 300 were carbon dioxide.</p>
<p>In February this year, atmospheric carbon dioxide reached <a href="https://www.esrl.noaa.gov/gmd/ccgg/trends/">414.1 parts per million</a>. Total greenhouse gas level – carbon dioxide, methane and nitrous oxide combined – reached almost <a href="https://www.esrl.noaa.gov/gmd/aggi/">500 parts per million of carbon dioxide-equivalent</a></p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=562&fit=crop&dpr=1 600w, https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=562&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=562&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=706&fit=crop&dpr=1 754w, https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=706&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/324842/original/file-20200402-74904-1jce5z4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=706&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Author provided/The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Carbon dioxide is now pouring into the atmosphere at a rate of <a href="https://www.esrl.noaa.gov/gmd/ccgg/trends/">two to three parts per million each year</a>. </p>
<p>Using carbon records stored in fossils and organic matter, I have determined that current carbon emissions constitute an extreme event in the recorded history of Earth.</p>
<p><a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13342">My research</a> has demonstrated that annual carbon dioxide emissions are now faster than after both the asteroid impact that eradicated the dinosaurs (about 0.18 parts per million CO2 per year), and the thermal maximum 55 million years ago (about 0.11 parts per million CO2 per year).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=524&fit=crop&dpr=1 754w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=524&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=524&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An asteroid wiped out the dinosaurs 66 million years ago.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>The next mass extinction has begun</h2>
<p>Current atmospheric concentrations of carbon dioxide are not yet at the levels seen 55 million and 65 million years ago. But the massive influx of carbon dioxide means the climate is changing faster than many plant and animal species <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.13342">can adapt</a>.</p>
<p><a href="https://www.un.org/sustainabledevelopment/blog/2019/05/nature-decline-unprecedented-report/">A major United Nations report</a> released last year warned around one million animal and plant species were threatened with extinction. Climate change was listed as one of five key drivers. </p>
<p>The report said the distributions of 47% of land-based flightless mammals, and almost 25% of threatened birds, may already have been negatively affected by climate change.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-effect-did-the-asteroid-that-wiped-out-the-dinosaurs-have-on-plants-and-trees-132386">Curious Kids: What effect did the asteroid that wiped out the dinosaurs have on plants and trees?</a>
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<p>Many researchers fear the climate system is approaching a <a href="https://www.pnas.org/content/115/33/8252">tipping point</a> - a threshold beyond which rapid and irreversible changes will occur. This will create a cascade of <a href="https://sites.hks.harvard.edu/sed/docs/hjs_esa_environment_0510.pdf">devastating effects</a>.</p>
<p>There are already signs tipping points have been reached. For example, <a href="https://www.theguardian.com/environment/2018/feb/27/arctic-warming-scientists-alarmed-by-crazy-temperature-rises">rising Arctic temperatures</a> have led to <a href="https://www.jpl.nasa.gov/news/news.php?feature=7616">major ice melt</a>, and weakened the <a href="https://www.globalresearch.ca/melting-ice-sheets-and-weakened-polar-fronts-onset-of-climate-tipping-points/5668981">Arctic jet stream</a> – a powerful band of westerly winds.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=469&fit=crop&dpr=1 600w, https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=469&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=469&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=589&fit=crop&dpr=1 754w, https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=589&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/324802/original/file-20200402-23115-hbrt5q.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=589&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A diagram showing the weakening Arctic jet stream, and subsequent movements of warm and cold air.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>This allows north-moving warm air to cross the polar boundary, and cold fronts emanating from the poles to <a href="https://link.springer.com/article/10.1007%2Fs10584-019-02458-x">intrude south into Siberia, Europe and Canada</a>. </p>
<p>A shift in climate zones is also causing the tropics to expand and migrate toward the poles, at a rate of about <a href="https://theconversation.com/the-worlds-tropical-zone-is-expanding-and-australia-should-be-worried-77701">56 to 111 kilometres per decade</a>. The tracks of tropical and extra-tropical cyclones are likewise shifting toward the poles. Australia is highly vulnerable to this shift.</p>
<h2>Uncharted future climate territory</h2>
<p><a href="https://www.nature.com/articles/nature16494">Research</a> released in 2016 showed just what a massive impact humans are having on the planet. It said while the Earth might naturally have entered the next ice age in about 20,000 years’ time, the heating produced by carbon dioxide would result in a period of super-tropical conditions, delaying the next ice age to about 50,000 years from now.</p>
<p>During this period, chaotic <a href="https://www.bloomsbury.com/us/storms-of-my-grandchildren-9781608195022/">high-energy stormy conditions</a> would prevail over much of the Earth. <a href="https://www.springer.com/gp/book/9783319572369">My research suggests</a> humans are likely to survive best in sub-polar regions and sheltered mountain valleys, where cooler conditions would allow flora and fauna to persist. </p>
<p>Earth’s next mass extinction is avoidable – if carbon dioxide emissions are dramatically curbed and we develop and deploy technologies to <a href="http://www.ecosmagazine.com/?act=view_file&file_id=EC147p14.pdf">remove carbon dioxide from the atmosphere</a>. But on the current trajectory, human activity threatens to make large parts of the Earth <a href="https://www.goodreads.com/book/show/41552709-the-uninhabitable-earth">uninhabitable</a> - a planetary tragedy of our own making. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/anatomy-of-a-heatwave-how-antarctica-recorded-a-20-75-c-day-last-month-134550">Anatomy of a heatwave: how Antarctica recorded a 20.75°C day last month</a>
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</em>
</p>
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<img src="https://counter.theconversation.com/content/130869/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Glikson does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The risks to nature from man-made global warming – and the imperative to act – are clear.Andrew Glikson, Earth and paleo-climate scientist, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1323862020-03-02T12:43:49Z2020-03-02T12:43:49ZCurious Kids: What effect did the asteroid that wiped out the dinosaurs have on plants and trees?<figure><img src="https://images.theconversation.com/files/317802/original/file-20200228-24672-crbw2j.jpg?ixlib=rb-1.1.0&rect=9%2C4%2C3086%2C2315&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/asteroid-that-wiped-out-dinosaurs-175507538">Esteban De Armas/Shutterstock</a></span></figcaption></figure><p><strong>Did plants and trees survive when the dinosaurs were wiped out? – Max, aged nine, UK</strong></p>
<p>One June day 66 million years ago, a massive asteroid crashed into the coast of Mexico. The asteroid crash caused what we call the Cretaceous-Palaeogene or K-Pg mass extinction. This killed <a href="https://theconversation.com/curious-kids-what-is-a-species-107402">species</a> around the world. <a href="https://royalsocietypublishing.org/doi/10.1098/rstb.1994.0045">Three-quarters of the animals in the ocean</a> and all of the dinosaurs apart from birds died in this mass extinction. </p>
<hr>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/282267/original/file-20190702-126345-1np1y7m.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
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<p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series by <a href="https://theconversation.com/uk">The Conversation</a>, which gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskids@theconversation.com">curiouskids@theconversation.com</a>. We won’t be able to answer every question, but we’ll do our very best.</em></p>
<hr>
<p>Plants and trees survived the mass extinction, one of the largest in the Earth’s history. So, we know the effects on plants were less than those on dinosaurs. Still, plants were not left unscathed by the event.</p>
<p>Scientists study fossils to learn about the effects of the K-Pg mass extinction. Fossils from North America tell the story of plant life before, during and after the asteroid impact. These fossils show that the immediate effects of the asteroid were catastrophic. The shockwaves, earthquakes and tsunamis would have killed many plants. Forest fires may have burnt large areas. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/317779/original/file-20200228-24685-jyu9tn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/317779/original/file-20200228-24685-jyu9tn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/317779/original/file-20200228-24685-jyu9tn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/317779/original/file-20200228-24685-jyu9tn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/317779/original/file-20200228-24685-jyu9tn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/317779/original/file-20200228-24685-jyu9tn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/317779/original/file-20200228-24685-jyu9tn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The asteroid hits the earth.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/8/8c/Chicxulub_impact_-_artist_impression.jpg">NASA</a></span>
</figcaption>
</figure>
<p>Around half of all plant species <a href="https://www.cambridge.org/core/journals/paleobiology/article/land-plant-extinction-at-the-end-of-the-cretaceous-a-quantitative-analysis-of-the-north-dakota-megafloral-record/88E2FDD040E1FA49CD1CBDACA71FEEF8">went extinct</a> after the asteroid hit Earth. While the immediate effects like tsunamis and shock waves killed some of these species, a great many more would have died as a result of the environmental effects of the asteroid impact.</p>
<h2>No sunshine</h2>
<p>By smashing into the Earth, the asteroid impact released huge amounts of dust into the atmosphere. This dust <a href="https://onlinelibrary.wiley.com/doi/epdf/10.1111/gto.12250">blocked the sun’s rays</a> from reaching the surface of the Earth and this is bad news for plants. We know the mass extinction <a href="https://www.nature.com/articles/352420a0">occurred in June</a> because flowers in a North American fossilised lily pond were in summer bloom when the asteroid hit. Because sunlight could not reach the Earth, what should have been summer in the northern hemisphere would have been more like a harsh winter. Freezing temperatures can kill plants, particularly those plants that live in water. </p>
<p>As well as freezing temperatures, the lack of sunlight had other effects on plants. With the sunlight blocked, plants would have no means for photosynthesis. This is the process plants use to convert the sun’s rays into energy and it is vital for life. With no photosynthesis, many plants species went extinct. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/317778/original/file-20200228-24690-1dlvgl2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/317778/original/file-20200228-24690-1dlvgl2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/317778/original/file-20200228-24690-1dlvgl2.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/317778/original/file-20200228-24690-1dlvgl2.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/317778/original/file-20200228-24690-1dlvgl2.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/317778/original/file-20200228-24690-1dlvgl2.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/317778/original/file-20200228-24690-1dlvgl2.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Ferns such as this wood fern (<em>Dryopteris</em>) flourished after the mass extinction.</span>
<span class="attribution"><span class="source">Mark Puttick</span></span>
</figcaption>
</figure>
<p>When trees and flowering plants were struggling, fern plants dominated the landscape. Ferns prosper in disturbed environments and only need the wind to colonise new areas. Plants with <a href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001949">fast life cycles</a> that grow and develop quickly also did well in these difficult times. These plants had the tools to cope with fast changes to their environments, unlike plants such as trees that need stable habitats.</p>
<h2>Plants survived better than animals</h2>
<p>Compared to animals, plants have an advantage in surviving mass extinctions. Plant seeds can remain dormant for many years in the soil. After the K-Pg mass extinction conditions were not right for plant growth, but plants could wait as seeds in a dormant state until things improve. This probably explains why plants did not suffer as much as animal groups in the extinction. Forests and other plants can regrow from their seeds after resting for decades. Animals can’t generally survive in dormant states for decades. Most animal groups took millions of years to recover from the mass extinction. Plants recovered fast. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/317781/original/file-20200228-24651-1mzhva4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/317781/original/file-20200228-24651-1mzhva4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=360&fit=crop&dpr=1 600w, https://images.theconversation.com/files/317781/original/file-20200228-24651-1mzhva4.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=360&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/317781/original/file-20200228-24651-1mzhva4.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=360&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/317781/original/file-20200228-24651-1mzhva4.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=452&fit=crop&dpr=1 754w, https://images.theconversation.com/files/317781/original/file-20200228-24651-1mzhva4.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=452&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/317781/original/file-20200228-24651-1mzhva4.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=452&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">All major groups of plants and flowers survived the mass extinction.</span>
<span class="attribution"><span class="source">Mark Puttick</span></span>
</figcaption>
</figure>
<p>The K-Pg 66 million years ago changed the course of the evolution of animals. As many species died, there were fewer animals competing against each other for food and other resources. Mammals could now freely use these resources and evolve into many different forms, including humans. The K-Pg mass extinction <a href="https://www.sciencedirect.com/science/article/pii/S016953470700256X">did not change the course of plant evolution</a>. Flowers and all groups of plants lived through the extinction. The mass extinction was traumatic for plants but they survived the hard times. Fortunately for the Earth – and for us – they did not go the same way as the non-bird dinosaurs.</p>
<hr>
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<p class="fine-print"><em><span>Mark Puttick receives funding from Royal Commission for the Exhibition of 1851. </span></em></p>A mass extinction 66 million years ago killed the non-bird dinosaurs, but plants survived.Mark Puttick, Research Fellow, Milner Centre for Evolution, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1293442020-01-06T04:01:10Z2020-01-06T04:01:10ZBushfires have reshaped life on Earth before. They could do it again<p>The catastrophic bushfires raging across much of Australia have not only taken a huge human and economic toll, but also delivered heavy blows to <a href="https://www.sciencemag.org/news/2019/12/fires-rage-across-australia-fears-grow-rare-species">biodiversity</a> and ecosystem function. </p>
<p>Already, scientists are warning of <a href="https://www.theguardian.com/environment/2020/jan/04/ecologists-warn-silent-death-australia-bushfires-endangered-species-extinction">catastrophic extinctions</a> of animals and plants. </p>
<p>Humans have seldom if ever seen fires like these, but we do know that wildfires have driven mass extinctions and reshaped life on Earth at least once before – when the asteroid strike that led to the demise of the dinosaurs sparked deadly global firestorms.</p>
<h2>Australian biodiversity</h2>
<p>Australia is one of only 17 “<a href="https://www.environment.gov.au/biodiversity/conservation/hotspots">megadiverse</a>” countries. Much of our species richness is concentrated in areas torched by the current bushfires.</p>
<p>While some mammals and birds face elevated extinction risk, things will be even worse for small, less mobile invertebrates (which make up the bulk of animal biodiversity). </p>
<p>For example, the Gondwana Rainforests of New South Wales and Queensland have been badly affected by the fires. These World Heritage listed forests are home to a <a href="http://world-heritage-datasheets.unep-wcmc.org/datasheet/output/site/gondwana-rainforests-of-australia/">rich diversity of insects</a> and a huge range of <a href="http://molluscanmusings.blogspot.com/2013/07/on-diversity-of-land-snails-down-under.html">land snails</a>, some restricted to tiny patches.</p>
<p>The bushfires have been rightly described as <a href="https://www.theguardian.com/australia-news/2019/nov/22/australia-bushfires-factcheck-are-this-years-fires-unprecedented">unprecedented</a>, and extinctions can play out over an <a href="https://en.wikipedia.org/wiki/Extinction_debt">extended period</a>. The full gravity of the impending catastrophe is not yet clear.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/bushfires-are-pushing-species-towards-extinction-54109">Bushfires are pushing species towards extinction</a>
</strong>
</em>
</p>
<hr>
<h2>Fire has driven extinctions before</h2>
<p>There have been greater burnings in the deep past, as we can see from the fossil record. They provide strong and disturbing evidence of how fire drove widespread extinctions that completely reshaped life on Earth.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/308540/original/file-20200105-11909-ahbx3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308540/original/file-20200105-11909-ahbx3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308540/original/file-20200105-11909-ahbx3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=419&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308540/original/file-20200105-11909-ahbx3g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=419&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308540/original/file-20200105-11909-ahbx3g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=419&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308540/original/file-20200105-11909-ahbx3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=526&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308540/original/file-20200105-11909-ahbx3g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=526&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308540/original/file-20200105-11909-ahbx3g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=526&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The ability to run fast and far was not enough to save dinosaurs from firestorms.</span>
<span class="attribution"><span class="source">Douglas Henderson</span></span>
</figcaption>
</figure>
<p>Around 66 million years ago, a mass die-off called the Cretaceous–Paleogene extinction event famously put an end to the reign of dinosaurs (sparing only birds). This event erased 75% of the planet’s species. </p>
<p><a href="https://www.cbsnews.com/news/how-dinosaurs-could-have-survived-killer-asteroid/">Scientists agree</a> these extinctions were primarily caused by an asteroid about 10 kilometres wide crashing into present-day Mexico, blasting a huge crater the size of Tasmania. </p>
<p>A <a href="https://www.independent.co.uk/news/science/asteroid-kill-dinosaurs-fifth-mass-extinction-endless-night-winter-18-month-rain-fire-ice-age-a7904491.html">nuclear winter</a> followed the impact, as fine particles thrown up into the atmosphere blocked sunlight for years. The extended frozen darkness killed ecosystems from plants and phytoplankton upwards.</p>
<p>Recent research shows that <a href="https://www.smithsonianmag.com/science-nature/what-happened-seconds-hours-weeks-after-dino-killing-asteroid-hit-earth-180960032/">global wildfires</a> were likely also an important driver of extinctions, at least for life on land. </p>
<p>The asteroid blasted flaming debris across the atmosphere. Massive deposits of soot found in the fossil record at this precise time suggest <em>most</em> of the Earth’s forests went up in smoke, though these cataclysmic calculations remain <a href="https://www.huffingtonpost.com.au/2015/01/23/asteroid-firestorm-dino-killing_n_6524024.html?ri18n=true">controversial</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/did-fire-kill-off-australias-megafauna-19679">Did fire kill off Australia's megafauna?</a>
</strong>
</em>
</p>
<hr>
<h2>Only animals that could escape fire survived</h2>
<p>The fossil record of land-dwelling animals – especially reptiles, birds and mammals – attests to the deadly efficiency of what has been dubbed the <a href="https://www.livescience.com/28582-asteroid-extinction-firestorm.html">dinosaur firestorm</a>. The nature of the victims and survivors is very relevant to current events.</p>
<p>The land animals that made it through the extinction all lived in ways that could confer <a href="http://www.spacedaily.com/news/deepimpact-04h.html">resilience to heat and fire</a>, such as living partly in water, being able to burrow or hide in deep crevices, or being able to escape rapidly by flight.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/308541/original/file-20200105-11929-x1n2ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308541/original/file-20200105-11929-x1n2ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308541/original/file-20200105-11929-x1n2ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=385&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308541/original/file-20200105-11929-x1n2ci.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=385&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308541/original/file-20200105-11929-x1n2ci.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=385&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308541/original/file-20200105-11929-x1n2ci.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=484&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308541/original/file-20200105-11929-x1n2ci.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=484&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308541/original/file-20200105-11929-x1n2ci.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=484&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Land vertebrates that survived the ancient wildfires were either amphibious (crocodiles, freshwater tortoises), small enough to burrow or shelter (early rodent-sized mammals), or both amphibious and burrowing (platypuses).</span>
<span class="attribution"><span class="source">Michael Lee</span></span>
</figcaption>
</figure>
<p>Among reptiles, crocodilians and freshwater tortoises (both amphibious) sailed through. Worm-lizards and burrowing snakes survived, but surface-dwelling lizards and snakes were <a href="https://www.livescience.com/25392-lizards-killed-dinosaur-extinction.html">hard hit</a>. </p>
<p>Among mammals, platypus-like monotremes (aquatic and burrowing) clung on, as did tiny rodent-like placental mammals (able to burrow, or hide in deep crevices), but all large placental mammals died. And while at least some birds survived, all their large, earth-bound, dinosaurian relatives perished. </p>
<p>In fact, it appears that every land-dwelling animal species larger than a domestic cat was <a href="https://www.theregister.co.uk/2016/06/20/mammals_nearly_wiped_out_in_asteroid_impact/">ultimately doomed</a>, unless it could swim, burrow or fly.</p>
<p>Even these abilities did not guarantee survival: they merely gave creatures a slightly better chance. For instance, pterosaurs could fly well, but still went extinct, along with most bird species. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/308542/original/file-20200105-11891-166jj79.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308542/original/file-20200105-11891-166jj79.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/308542/original/file-20200105-11891-166jj79.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=880&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308542/original/file-20200105-11891-166jj79.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=880&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308542/original/file-20200105-11891-166jj79.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=880&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308542/original/file-20200105-11891-166jj79.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1106&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308542/original/file-20200105-11891-166jj79.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1106&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308542/original/file-20200105-11891-166jj79.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1106&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Deforestation in ancient wildfires spared some ground-foraging birds but obliterated tree-dwelling, perching birds.</span>
<span class="attribution"><span class="source">Michael Lee</span></span>
</figcaption>
</figure>
<p><a href="https://www.theatlantic.com/science/archive/2018/05/dinosaurs-asteroids-goodbye-birds-trees/561110/">Recent research</a> suggests perching birds –- which need forests to live in –- were essentially eliminated when most of the world’s trees disappeared. The sole avian survivors were ground-foragers similar to chickens and rails, and it took millions of years for new perching birds (modern songbirds) to re-evolve.</p>
<p>By exterminating many species, and doing so highly selectively, the global wildfires (alongside other effects of the asteroid impact) totally restructured Earth’s biosphere.</p>
<h2>What about the current fires?</h2>
<p>The recent rampant bushfires are regional rather than global (e.g. Australia, the Amazon, Canada, California, Siberia), and are burning less land cover than the worst-case dinosaur firestorm scenario. </p>
<p>Yet their long-term extinction effects could also be severe, because our planet has already <a href="https://www.nationalgeographic.com/environment/global-warming/deforestation/">lost half its forest cover</a> due to humans. These fires are hitting shrunken biodiversity refuges that are simultaneously threatened by an anthropogenic cocktail of pollution, invasive feral species, and climate change.</p>
<p>The ancient catastrophe provides strong evidence, written in stone, that firestorms can contribute to extensive extinctions, even among large vertebrates with large distributions and high mobility. </p>
<p>It also shows certain types of organisms will bear the brunt of the impact. Entire guilds of similar species could vanish, severely impacting ecosystem function. </p>
<p>It took millions of years of regeneration and evolution for our planet’s biosphere to recover from the nuclear winter and wildfires of the asteroid impact. When a new world order eventually emerged, it was radically different: the age of dinosaurs gave way to the age of mammals and birds.</p><img src="https://counter.theconversation.com/content/129344/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mike Lee receives funding from The Australian Research Council (ARC).</span></em></p>The asteroid that wiped out the dinosaurs sparked global firestorms. On land, only creatures that could evade fire survivedMike Lee, Professor in Evolutionary Biology (jointly appointed with South Australian Museum), Flinders UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1255622019-12-06T02:39:35Z2019-12-06T02:39:35ZCurious Kids: how do we know if a dinosaur skeleton is from a child dinosaur or an adult dinosaur?<figure><img src="https://images.theconversation.com/files/297834/original/file-20191021-56234-13d8r5h.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3308%2C2164&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">This T. rex is very big, but was it a grown-up?</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><hr>
<blockquote>
<p><strong>When you find dinosaur skeletons, how can you tell how old the dinosaur was? Like, if the skeleton is from a child dinosaur or an adult dinosaur? – Henry, aged 8.</strong></p>
</blockquote>
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<p><a href="https://theconversation.com/au/topics/curious-kids-36782"><img src="https://images.theconversation.com/files/291898/original/file-20190911-190031-enlxbk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=90&fit=crop&dpr=1" width="100%"></a></p>
<p>Hi Henry, that’s a good but tricky question.</p>
<p>There are a couple of ways we can try to tell how old a dinosaur was when it died.</p>
<p>If you cut open a fossil dinosaur bone, you can see lines, just like if you were looking at rings in a tree. Trees rings happen when a tree grows slowly in a tough season like an icy cold winter. You can count the rings to see how many winters that tree has lived through. And because there is only one winter each year, then you know how many years old the tree is. Easy! </p>
<p>Animals, like dinosaurs, formed similar lines in their bones whenever they slowed down their growing. But there’s a catch: this might not happen once each year like in a tree.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-did-the-dinosaurs-die-111912">Curious Kids: why did the dinosaurs die?</a>
</strong>
</em>
</p>
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<p>Why would a dinosaur slow down its growing? A dinosaur might not grow very fast if there is not enough food to eat. This might happen if there hasn’t been much rain and so there are not as many plants around to eat. Or there might be loads of food around, but the dinosaur is using all its energy to fight other dinosaurs, rather than using it to grow. </p>
<p>There might be lots of times each year when the dinosaur stopped growing, and each time would make a growth line in its bones. So if you find a fossil with lots of growth lines, you might not be looking at the bones of a really old dinosaur, but a very busy, stressed-out dinosaur! So this is quite a complicated way to try and guess its age.</p>
<h2>Use your head</h2>
<p>Another way to try to guess the age of a dinosaur is to look at how its skull bones connect to each other. Lots of baby animals don’t have a solid skull. Instead, their skull is made up of different bits that gradually stick together into one piece as it grows. </p>
<p>We’re not sure whether baby dinosaurs had skulls that grew like this. Some scientists have tried to find out by looking at skulls from baby emus and alligators, both of which are a bit similar to dinosaurs. They discovered that emu chicks have skull bones that stick together as they grow, but baby alligators don’t! So that doesn’t really give us a clear answer either.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/299811/original/file-20191101-102199-9c8ln9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/299811/original/file-20191101-102199-9c8ln9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/299811/original/file-20191101-102199-9c8ln9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=256&fit=crop&dpr=1 600w, https://images.theconversation.com/files/299811/original/file-20191101-102199-9c8ln9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=256&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/299811/original/file-20191101-102199-9c8ln9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=256&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/299811/original/file-20191101-102199-9c8ln9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=321&fit=crop&dpr=1 754w, https://images.theconversation.com/files/299811/original/file-20191101-102199-9c8ln9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=321&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/299811/original/file-20191101-102199-9c8ln9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=321&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The growth of a dinosaur called Protoceratops, from newborn baby (on the left) to grown-up (on the right).</span>
<span class="attribution"><span class="source">Harry Nguyen/Wikimedia Commons</span></span>
</figcaption>
</figure>
<p>Sometimes it’s really easy to tell how old a dinosaur was. If you find a dinosaur egg, you can use something called X-rays to look inside it and see if there is a baby dinosaur fossil inside. If there is, you know that dinosaur was 0 years old! </p>
<p>Then, if you find a bigger fossil from the same kind of dinosaur nearby, there is a chance that dinosaur was the baby dinosaur’s grown-up parent. </p>
<p>If you find a baby and a grown-up together, you can learn lots more things by looking at the differences between the two. It might tell you how the dinosaur changes size and shape as it gets older. </p>
<p>You might find a dinosaur that looks like a mixture between the two. That might be a “big kid” dinosaur that is well on its way to becoming a grown-up.</p>
<p>It’s still hard to tell exactly how old each dinosaur was. But scientists are like detectives, and they have lots of clever ideas that are helping them get better at it all the time.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-did-the-velociraptors-have-feathers-119535">Curious Kids: did the velociraptors have feathers?</a>
</strong>
</em>
</p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au</em></p><img src="https://counter.theconversation.com/content/125562/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Caitlin Syme does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Sometimes the only way to tell the difference between a baby dinosaur and a grown-up one is to find fossils of them both together.Caitlin Syme, PhD in Vertebrate Palaeontology, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1223502019-09-13T12:16:30Z2019-09-13T12:16:30ZMass extinctions made life on Earth more diverse – and might again<figure><img src="https://images.theconversation.com/files/292398/original/file-20190913-8661-pz8pkg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/digging-fossil-skull-tyrannosaurus-rex-trex-422577346">Ton Bangkeaw/Shutterstock</a></span></figcaption></figure><p>In the past half-billion years, Earth has been hit <a href="https://theconversation.com/five-mass-extinctions-and-what-we-can-learn-from-them-about-the-planet-today-79971">again and again</a> by mass extinctions, wiping out most species on the planet. And every time, <a href="https://theconversation.com/how-life-on-earth-recovers-after-a-devastating-mass-extinction-43719">life recovered</a> and ultimately went on to increase in diversity. </p>
<p>Is life just incredibly resilient, or is something else going on? Could mass extinctions actually help life diversify and succeed – and if so, how? Given that we’re currently facing <a href="https://theconversation.com/earths-sixth-mass-extinction-has-begun-new-study-confirms-43432">another extinction event</a>, there’s extra urgency in trying to work out how mass extinctions affect diversity.</p>
<p>Mass extinction is probably the most striking pattern in the fossil record. Vast numbers of species – even entire families – disappear rapidly, simultaneously, around the world. Extinction on this scale usually requires some kind of global environmental catastrophe, so severe and so rapid that species can’t evolve, and instead disappear.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/289948/original/file-20190828-184234-denpa6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/289948/original/file-20190828-184234-denpa6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/289948/original/file-20190828-184234-denpa6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/289948/original/file-20190828-184234-denpa6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/289948/original/file-20190828-184234-denpa6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/289948/original/file-20190828-184234-denpa6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/289948/original/file-20190828-184234-denpa6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Catastrophic eruptions are the main driver of mass extinctions.</span>
<span class="attribution"><span class="source">Wikipedia</span></span>
</figcaption>
</figure>
<p>Massive volcanic eruptions drove the extinctions at the end of the Devonian, <a href="https://science.sciencemag.org/content/269/5229/1413">Permian</a> and <a href="https://science.sciencemag.org/content/340/6135/941">Triassic</a> periods. Global cooling and <a href="https://science.sciencemag.org/content/331/6019/903">intense glaciation</a> drove the Ordivician-Silurian extinctions. An <a href="https://theconversation.com/how-does-an-invisible-underwater-crater-prove-an-asteroid-killed-the-dinosaurs-57711">asteroid caused</a> the end-Cretaceous extinction of the dinosaurs. These “Big Five” extinctions get the most attention because, well, they’re the biggest. But lots of lesser yet still civilisation-threatening events occurred as well, like the pulse of extinction <a href="https://science.sciencemag.org/content/324/5931/1179">before the end-Permian event</a>.</p>
<p>These events were indescribably destructive. The Chicxulub asteroid impact that ended the Cretaceous period shut down photosynthesis for years and caused decades of <a href="https://theconversation.com/did-a-burning-oil-spill-wipe-out-the-dinosaurs-62456">global cooling</a>. Anything that couldn’t shelter from the cold, or find food in the darkness – which was most species – perished. Perhaps <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/jeb.12882">90% of all species</a> disappeared in just a few years.</p>
<p>But life bounced back and the recovery was rapid. 90% of mammal species were eliminated by the asteroid, but they recovered and then some <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/jeb.12882">within 300,000 years</a>, going on to evolve into horses, whales, bats and our primate ancestors. <a href="https://www.nature.com/articles/nature15697">Birds</a> and <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0073535">fish</a> experienced similarly rapid recovery and radiation. And many other organisms – snakes, tuna and swordfish, butterflies and ants, grasses, orchids and asters – evolved or diversified at the same time.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/289946/original/file-20190828-184217-wh14ae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/289946/original/file-20190828-184217-wh14ae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=427&fit=crop&dpr=1 600w, https://images.theconversation.com/files/289946/original/file-20190828-184217-wh14ae.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=427&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/289946/original/file-20190828-184217-wh14ae.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=427&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/289946/original/file-20190828-184217-wh14ae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=537&fit=crop&dpr=1 754w, https://images.theconversation.com/files/289946/original/file-20190828-184217-wh14ae.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=537&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/289946/original/file-20190828-184217-wh14ae.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=537&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Butterflies and asters both diversified in the wake of the end-mass extinction.</span>
<span class="attribution"><span class="source">wikipedia</span></span>
</figcaption>
</figure>
<p>This pattern of recovery and diversification happened after every mass extinction. The end-Permian extinction saw mammal-like species take a hit, but reptiles <a href="https://www.nature.com/articles/nature08718">flourished afterward</a>. After the reptiles suffered during the end-Triassic event, the surviving dinosaurs took over the planet and <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsbl.2008.0441">diversified</a>. Although a mass extinction ended the dinosaurs, they only evolved in the first place because of mass extinction.</p>
<p>Despite this chaos, life slowly diversified over the past 500m years. In fact, several things hint that extinction drives this increased diversity. For one, the most rapid periods of diversity increase occur immediately <a href="https://science.sciencemag.org/content/215/4539/1501/tab-pdf">after mass extinctions</a>. But perhaps more striking, recovery isn’t only driven by an increase in species numbers. </p>
<p>In a recovery, animals innovate – finding new ways of making a living. They exploit new habitats, new foods, new means of locomotion. For example, our fish-like forebears <a href="https://www.nature.com/articles/nature00824">first crawled onto land</a> after the end-Devonian extinction.</p>
<h2>Evolutionary innovation</h2>
<p>Extinction doesn’t only drive this process of speciation. It also drives evolutionary innovation. It’s not a coincidence that the biggest pulse of innovation in life’s history – the evolution of complex animals in the <a href="https://theconversation.com/exquisite-fossil-finds-shed-new-light-on-the-cambrian-explosion-when-oceans-first-filled-with-complex-animal-life-114054">Cambrian Explosion</a> – happened in the wake of the <a href="https://www.sciencedirect.com/science/article/abs/pii/S016953471830140X">extinction of the Ediacaran</a> animals that went before them.</p>
<p>Innovation may increase the number of species that can coexist because it allows species to move into new niches, instead of fighting over the old ones. Fish crawling onto land didn’t compete with fish in the seas. Bats hunting at night with sonar didn’t compete with birds that were active during the day. Innovation means evolution isn’t a zero-sum game. Species can diversify without driving others extinct. But why does extinction drive innovation? </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/289947/original/file-20190828-184217-71hgk9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/289947/original/file-20190828-184217-71hgk9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=365&fit=crop&dpr=1 600w, https://images.theconversation.com/files/289947/original/file-20190828-184217-71hgk9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=365&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/289947/original/file-20190828-184217-71hgk9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=365&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/289947/original/file-20190828-184217-71hgk9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=458&fit=crop&dpr=1 754w, https://images.theconversation.com/files/289947/original/file-20190828-184217-71hgk9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=458&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/289947/original/file-20190828-184217-71hgk9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=458&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Over 1,000 bat species have evolved without directly competing with birds.</span>
<span class="attribution"><span class="source">Wikipedia</span></span>
</figcaption>
</figure>
<p>Stable ecosystems may prevent innovation. A modern wolf is probably a far more dangerous predator than a velociraptor, but a tiny mammal couldn’t evolve into a wolf in the Cretaceous because there were velociraptors. Any experiments in carnivory would have ended badly, with the poorly adapted mammal competing with – or just eaten by – the already well-adapted <em>Velociraptor</em>. </p>
<p>But, in the lulls after an extinction, evolution may be able to experiment with designs that are initially poorly adapted, but with long-term potential. With the show’s stars gone, the evolutionary understudies get their chance to prove themselves.</p>
<p>The extinction of <em>Velociraptor</em> gave mammals the freedom to experiment with new niches. Initially, they were poorly equipped for a predatory lifestyle, but without dinosaurs competing with or eating them, they didn’t need to be terribly good to survive. They only needed to be as good as the other things around at the time. So they flourished in an ecological vacuum, ultimately evolving into big, fast, intelligent pack hunters. </p>
<h2>Creative destruction</h2>
<p>Life isn’t just resilient, it thrives on adversity. Life will <a href="https://theconversation.com/the-sixth-mass-genesis-new-species-are-coming-into-existence-faster-than-ever-thanks-to-humans-80527">even recover</a> from the <a href="https://theconversation.com/5-periods-of-mass-extinction-on-earth-are-we-entering-the-sixth-57575">current wave</a> of human-induced extinctions. If we disappeared tomorrow, then species would evolve to replace woolly mammoths, dodo birds and the passenger pigeon, and life would likely become even more diverse than before. That’s not to justify complacency. It won’t happen in our lifetime, or even the lifetime of our species, but millions of years from now.</p>
<p>This idea that extinction drives innovation may even apply to human history. The extinction of ice-age megafauna must have decimated hunter-gatherer bands, but it also may have given <a href="https://www.amazon.co.uk/Plagues-People-William-McNeill/dp/0385121229">farming a chance to develop</a>. The Black Death produced untold human suffering, but the shakeup of political and economic systems may have led to <a href="https://www.oxfordbibliographies.com/view/document/obo-9780195399301/obo-9780195399301-0062.xml">the Renaissance</a>. </p>
<p>Economists talk about <a href="https://www.jstor.org/stable/1885348?seq=1#page_scan_tab_contents">creative destruction</a>, the idea that creating a new order means destroying the old one. But evolution suggests there’s another kind of creative destruction, where the destruction of the old system creates a vacuum and actually drives the creation of something new and often better. When things are at their worst is precisely when the opportunity is the greatest.</p><img src="https://counter.theconversation.com/content/122350/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas R. Longrich does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Every cloud has a silver lining – even the debris cloud from an asteroid impactNicholas R. Longrich, Senior lecturer, palaeontology, Milner Centre for Evolution, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1119122019-06-12T03:40:15Z2019-06-12T03:40:15ZCurious Kids: why did the dinosaurs die?<figure><img src="https://images.theconversation.com/files/259634/original/file-20190219-121760-jndqte.jpg?ixlib=rb-1.1.0&rect=3%2C3%2C1019%2C679&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Around 66 million years ago, a huge rock from outer space (called an asteroid) smashed into the Earth.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/chealion/4787266142/in/photolist-8i2Zrq-6yhEzK-kQZ1cn-kQZ5me-kQYh9r-kR1c4S-4mXKER-8v51D3-22chBV9-kQYbqc-6MhkYq-8EZ3SY-kQZ4Mi-zUcep-8v524A-cANWo3-8URBwf-b5VXh-9KZTKY-9Svepu-RDbtfs-yawwY-yyftdR-atKBrA-gYpZXV-kQYbG4-71niK4-kR1cE1-kQYZM4-kQYdkz-4JHWfE-8JmrUY-4JBsZ4-6VnsNQ-4JHWdh-eUc9q1-bnwDbe-8jvbVw-4JDFMP-25wNRz-8jrXKX-8HeWz-9ry3tM-6LDbfG-byBuxi-52EqQi-4a2qFU-4V3MN7-8BxKL-9MNcZg">Michael J/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series for children. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.edu.au You might also like the podcast <a href="http://www.abc.net.au/kidslisten/imagine-this/">Imagine This</a>, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.</em> </p>
<hr>
<blockquote>
<p><strong>Why did the dinosaurs die? – Whitaker, age 4.</strong></p>
</blockquote>
<hr>
<p>That’s a great, and tricky question!</p>
<p>We know that dinosaurs ruled the Earth for about 180 million years. Then, around 66 million years ago, a huge rock from outer space (called an asteroid) smashed into the Earth.</p>
<p>It crash-landed near Mexico. It shook the ground. It made big waves in the sea.
Any animals and plants that were nearby would have gotten squashed or washed away!</p>
<p>The asteroid made lots of dust and dirt and rocks to fly up into the air. All that dust and dirt covered the planet and made the sky dark. There were many forest fires too.</p>
<p>Before the asteroid hit Earth, there were lots of volcanoes erupting in what we now call India. They made smoke, and ash, and gases fill up the air. We are not sure if the asteroid then hitting Earth made more volcanoes erupt. Maybe it was just very bad timing.</p>
<h2>From cold to hot</h2>
<p>It was so dusty and dark that the warm sunshine couldn’t reach the ground.
This made the Earth very cold. </p>
<p>But after the dust settled and the sun came out, the Earth got very hot indeed. The sea creatures, plants, and land animals didn’t like that very much. The plants probably had a hard time growing. The plant-eating animals ran out of plants to eat, and then the animals that ate other animals also ran out of food. So it became very hard for dinosaurs to survive.</p>
<p>But it’s still really hard to know for sure exactly why the dinosaurs died. Dinosaur-scientists (palaeontologists) still wonder whether it was because of the asteroid, or the volcanoes, or both the asteroid and volcanoes. Did the animals get too cold or too hot? Did they run out of food?</p>
<p>We might not ever know for sure, but we will always keep looking for answers!</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/279056/original/file-20190612-32342-1eupnsr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/279056/original/file-20190612-32342-1eupnsr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/279056/original/file-20190612-32342-1eupnsr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/279056/original/file-20190612-32342-1eupnsr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/279056/original/file-20190612-32342-1eupnsr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/279056/original/file-20190612-32342-1eupnsr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/279056/original/file-20190612-32342-1eupnsr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/279056/original/file-20190612-32342-1eupnsr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Here is a life-size skeleton of Muttaburrasaurus in the Queensland Museum. Muttaburrasaurus was a large, plant-eating dinosaur that lived in eastern Australia.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-many-dinosaurs-in-total-lived-on-earth-during-all-periods-100460">Curious Kids: How many dinosaurs in total lived on Earth during all periods?</a>
</strong>
</em>
</p>
<hr>
<h2>Who went extinct and who didn’t?</h2>
<p>Most of the dinosaurs died. We call this going “extinct”. An animal is extinct when it doesn’t exist anymore anywhere in the world.</p>
<p>It wasn’t just most dinosaurs that went extinct 66 million years ago. Among others that went extinct were: flying reptiles called pterosaurs, huge reptiles that swam in the ocean called plesiosaurs and pliosaurs, creatures with curled, spiral shells called ammonites, and lots of other plants and animals. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/279049/original/file-20190612-32335-1ejb6fd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/279049/original/file-20190612-32335-1ejb6fd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/279049/original/file-20190612-32335-1ejb6fd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=471&fit=crop&dpr=1 600w, https://images.theconversation.com/files/279049/original/file-20190612-32335-1ejb6fd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=471&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/279049/original/file-20190612-32335-1ejb6fd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=471&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/279049/original/file-20190612-32335-1ejb6fd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=592&fit=crop&dpr=1 754w, https://images.theconversation.com/files/279049/original/file-20190612-32335-1ejb6fd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=592&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/279049/original/file-20190612-32335-1ejb6fd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=592&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Here’s an artist’s impression of a pterosaurs.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/279052/original/file-20190612-32342-1o6m4g6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/279052/original/file-20190612-32342-1o6m4g6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/279052/original/file-20190612-32342-1o6m4g6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/279052/original/file-20190612-32342-1o6m4g6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/279052/original/file-20190612-32342-1o6m4g6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/279052/original/file-20190612-32342-1o6m4g6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/279052/original/file-20190612-32342-1o6m4g6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/279052/original/file-20190612-32342-1o6m4g6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Huge reptiles called plesiosaurs once swam in the ocean.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<p>But others survived. Different types of insects, lizards, crocodiles, mammals, birds, sharks, fish, crabs, snails, flowers, ferns and trees all made it through. </p>
<p>How? We don’t really know.</p>
<p>It could be because the animals were small and didn’t need much food. Maybe it was because they could eat crunchy seeds the dead plants left behind, or mushrooms growing on the dead plants, or tiny scraps of old, dry meat. Maybe it was because they could burrow into the ground to keep warm. Maybe it was because they could swim far away to keep safe. And maybe some of those dry, crunchy seeds could grow into plants after they were buried for a long time.</p>
<p>But we know they survived.</p>
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<a href="https://images.theconversation.com/files/279054/original/file-20190612-32361-1pkz3xe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/279054/original/file-20190612-32361-1pkz3xe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/279054/original/file-20190612-32361-1pkz3xe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/279054/original/file-20190612-32361-1pkz3xe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/279054/original/file-20190612-32361-1pkz3xe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/279054/original/file-20190612-32361-1pkz3xe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/279054/original/file-20190612-32361-1pkz3xe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/279054/original/file-20190612-32361-1pkz3xe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Woolly mammoths once roamed the Earth.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<p>Those animals and plants found new homes. And as the plants grew bigger and stronger, the animals could grow bigger too. They could take the place of the big dinosaurs that had died. Big woolly mammoths, giant kangaroos, and whales now roamed the land and sea. New types of plants grew, like grass. And a long time later, human beings evolved – that’s us!</p>
<p>Now mammals rule the Earth.</p>
<h2>Not all the dinosaurs died</h2>
<p>Did you know that not all the dinosaurs went extinct 66 million years ago? They’re not the type of dinosaurs you might be thinking of, like <em>Tyrannosaurus</em>, or <em>Brachiosaurus</em>, or <em>Muttaburrasaurus</em>. The dinosaurs that survived were… birds!</p>
<p>That’s right! All birds are actually dinosaurs.</p>
<p>Ancient birds lived beside other dinosaurs. They survived the asteroid and volcanoes. And now birds live alongside us today.</p>
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Read more:
<a href="https://theconversation.com/curious-kids-are-mermaids-real-99140">Curious Kids: Are mermaids real?</a>
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<p>I think it’s sad that all the other dinosaurs went extinct so long ago. But we can remember them by visiting museums and looking at fossils, or by reading books about them, or by watching birds fly through the sky.</p>
<p>But if it weren’t for all the other dinosaurs going extinct so long ago, fluffy little mammals wouldn’t have had room to grow and evolve. And there wouldn’t be any humans.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/9GVvtKK5sFw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Today’s birds evolved from prehistoric times. Birds survived the asteroid that led to the extinction of dinosaurs.</span></figcaption>
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<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au</em></p>
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em>Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/111912/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Caitlin Syme does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Dinosaurs ruled the Earth for about 180 million years. But around 66 million years ago, a huge rock from outer space (called an asteroid) smashed into the Earth. Then things got worse for dinosaurs.Caitlin Syme, PhD Candidate, Vertebrate Palaeontology, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1147532019-04-04T00:23:19Z2019-04-04T00:23:19ZA ‘seiche’ wave can outpace a tsunami, and both can be triggered by meteorites and earthquakes<figure><img src="https://images.theconversation.com/files/267244/original/file-20190403-177184-r6mkdz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Waves can be generated in lakes and other bodies of water when seismic energy travels through land. </span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/_asfY_cHGNk">Leo Roomets / Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>A catastrophic event occurred on Earth 66 million years ago. A huge meteorite struck our planet in what is now Mexico, triggering mass extinctions of the dinosaurs and most other living creatures. </p>
<p>A new paper shows the <a href="https://www.pnas.org/content/early/2019/03/27/1817407116">first recorded victims</a> of this impact were fish and other marine animals, stranded by a wave that left them high and dry in an ancient river in North Dakota, at a site called Tanis. </p>
<p>For scientists unpacking the evidence around the event, a full picture of the cataclysm has involved looking into the details of planetary surface physics during giant impacts. </p>
<p>But beyond the first layer of fascinating results – <a href="https://www.abc.net.au/news/2019-04-02/research-into-the-day-the-dinosaurs-died/10960446">little glass impact beads stuck in the gills of fish</a>, for example – one really interesting aspect of this work is around how water behaves when it’s exposed to extreme forces.</p>
<p>If you’ve never heard of a form of wave called a seiche, this is your chance to catch up. </p>
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<figcaption><span class="caption">This is a seiche – a standing wave – in a swimming pool, during a large earthquake in Nepal.</span></figcaption>
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<h2>Waves of damage</h2>
<p>The Chicxulub meteorite crater in coastal Mexico is strongly associated with the mass extinction of the dinosaurs (<a href="https://www.pnas.org/content/115/23/5820">and 75% of all species</a>), 66 million years ago. </p>
<p>The first victims were right at the site. Any marine creatures close to the point of impact would have been instantly <a href="https://www.nature.com/articles/ngeo2095">vaporised</a> (sadly leaving no fossil record), along with much of the surrounding rock. </p>
<p>Around the periphery, the energy of the impact melted and ejected tonnes of molten rock, which together with condensing rock vapour, formed little glass beads (“<a href="https://www.lpi.usra.edu/science/kring/Chicxulub/discovery/">impact spherules</a>”) that can be found in a layer around the world at this time. </p>
<p>The shock wave itself pulverised the adjacent rock enough to metamorphise it, forming features like “shocked quartz” – fractured quartz indicative of enormous pressures. It carried the energy equivalent of a magnitude 11 earthquake – 1,000 times more energy than the <a href="https://www.abc.net.au/news/2014-12-24/boxing-day-tsunami-how-the-disaster-unfolded/5977568">2004 Boxing Day quake</a> which killed almost 230,000 people. </p>
<h2>Vast inland sea now gone</h2>
<p>North Dakota is more than 3,000km away from the Chicxulub crater, and was a similar distance at the time of the meteorite impact event. </p>
<p>Separating them back then, however, was a vast inland sea that covered much of midwest USA, from Texas up to the Dakotas. Feeding into that inland sea was a river system upon which the Tanis site in North Dakota was formed. This site has preserved the earliest recorded deaths of the Chicxulub impact. </p>
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<img alt="" src="https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=555&fit=crop&dpr=1 600w, https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=555&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=555&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=697&fit=crop&dpr=1 754w, https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=697&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/267254/original/file-20190403-177167-a3fgiw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=697&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Different views of the Tanis site. A: Tanis (starred) within a regional context (large map) and on a national map (inset). B: Photo and interpretive overlay of an oblique cross-section through Tanis. C: Simplified schematic depicting the general deposits at the site (not to scale). Most fish carcasses were found at point 3.</span>
<span class="attribution"><a class="source" href="https://www.pnas.org/content/early/2019/03/27/1817407116">Robert A DePalma and colleagues</a></span>
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<p>The site itself is unusual. The deposition of sediments can tell us about the flow of water in the river. </p>
<p>Most ripples (or <a href="https://blogs.egu.eu/divisions/ts/2016/10/17/soft-sediment-structures-slumps-and-flames/">flame structures</a>) indicate a southerly flow of the river before and after the Tanis deposit. However, these flow indicators point the wrong way during the time the Tanis unit formed. Water was flowing upstream, fast. </p>
<p>At the site are also found the fossilised remains of species, like sharks and rays, that occupied brackish water, rather than the freshwater of the stream. These had to be brought inland from the sea by something, and left to die, smothered in sediment, on a riverbank. </p>
<h2>Stranded in Dakota</h2>
<p>The obvious candidate is an impact tsunami. Perhaps the impact of the meteorite hitting the ocean generated a huge wave that carried fish from the inland sea, and against the flow of fresh water, to leave the creatures stranded in Dakota? </p>
<p>But there are problems with this hypothesis. The tiny impact spherules that formed in Chicxulub can be found throughout the deposit (many clogging the gills of fish), and pockmarks in the sedimentary layers means rocks were still raining down. This means the surge of water occurred within around 15 minutes to two hours of the impact itself.</p>
<p>For a tsunami to travel the 3,000km from the point of impact, to the Tanis site across the inland sea, would have taken almost 18 hours. Something else killed these creatures.</p>
<p>The seismic waves from the impact would have travelled through the Earth much faster than a tsunami travelled across water – and arrived near Tanis between 6-13 minutes later. The <a href="https://www.pnas.org/content/early/2019/03/27/1817407116">authors of the Tanis study</a> suggest these seismic waves may have triggered an unusual type of wave in the inland sea, called a seiche. </p>
<h2>Standing waves</h2>
<p>Seiches are <a href="https://commons.wikimedia.org/wiki/File:Standing_wave_2.gif">standing waves</a> in bodies of water, and are often found in large lake systems <a href="https://www.youtube.com/watch?v=SwLGX21Jflo">during strong winds</a>. The winds themselves cause waves and water displacement, which can have a harmonic effect, causing the water to slosh side to side like an <a href="https://www.youtube.com/watch?v=bYI1zIjJr4g">overfull bathtub</a>. </p>
<p>However, earthquakes are also known to cause seiches. Particularly dramatic seiches are often seen in <a href="https://www.youtube.com/watch?v=Z7kNr354PJs">swimming pools during large quakes</a>. The interaction of the seismic wave’s period (the time between two waves) with the timescale of waves sloshing in a pool can amplify their effect. </p>
<p>But seiches can affect larger bodies of water too. </p>
<p>During the 2011 Tohuku earthquake in Japan, seiches <a href="https://www.youtube.com/watch?v=uYJjMqYdmmo">over 1m high</a> were observed in Norwegian fjords more than 8,000km away. With an energy more than 1,000 times greater, the Chicxulub event could quite conceivably have generated bigger than 10 metre swells in the North American inland sea – the scale implied by the deposition of the Tanis site. </p>
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<figcaption><span class="caption">These waves in Norwegian fjords were created by seismic waves from the 2011 Tohoku earthquake in Japan.</span></figcaption>
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<p>Given a seiche can be driven by seismic waves, it’s conceivable that one drove the surge that stranded marine creatures at Tanis, resulting in the short time between the impact debris and the surge deposit. </p>
<h2>Still lots of questions</h2>
<p>But a lot remains unclear regarding exactly what did happen 66 million years ago. </p>
<p>Could the fish stranding have been driven by the first seismic activity to appear at Tanis (the <a href="https://www.sciencedirect.com/science/article/pii/S0264370716301089">P and S waves</a> in science parlance, which travel through the interior of the Earth, arriving at Tanis 6 and 10 minutes after impact, respectively), or the more destructive but slower surface waves at the top of the Earth’s crust, which arrived 13 minutes after impact? </p>
<p>How might seiche waves have interacted with <a href="https://www.lpi.usra.edu/meetings/lpsc2005/pdf/1544.pdf">global hurricane-strength wind storms</a> caused by the impact? </p>
<p>Would the period of sloshing of a seiche be consistent with the scale of the inland sea? (The inland sea was much larger than most lakes seiches are traditionally observed in – and may or may not have been open to the ocean). Given so little is really known about the dimensions of the inland sea, this is hard to constrain. </p>
<p>The Tanis site has given us an incredible window into the first few hours of a mass-extinction. But it has also highlighted how little we have probed into the fatal surface physics of these extreme events.</p><img src="https://counter.theconversation.com/content/114753/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Craig O'Neill has received past funding from the ARC. </span></em></p>If you’ve never heard of a form of wave called a ‘seiche’ – which can occur in swimming pools during earthquakes – this is your chance to catch up.Craig O'Neill, Director of the Macquarie Planetary Research Centre/Associate Professor in Geodynamics, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1121342019-02-21T19:06:05Z2019-02-21T19:06:05ZHow the dinosaurs went extinct: asteroid collision triggered potentially deadly volcanic eruptions<figure><img src="https://images.theconversation.com/files/260092/original/file-20190221-148542-149z4bm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An artist's impression of an asteroid about to hit Earth: it's what happens next that could have helped wipe out the dinosaurs 66 million years ago.</span> <span class="attribution"><span class="source">Shutterstock/Mopic</span></span></figcaption></figure><p>It’s almost 40 years since scientists discovered what wiped out the dinosaurs: an asteroid hitting Earth near modern-day Mexico. That was it, or so we thought.</p>
<p>A paper published today in <a href="http://science.sciencemag.org/content/363/6429/866" title="The eruptive tempo of Deccan volcanism in relation to the Cretaceous-Paleogene boundary">Science</a> further supports an alternative hypothesis: that catastrophic events following the impact could have helped cause the end of the dinosaurs and many other forms of life.</p>
<p>This builds on earlier work – including some published <a href="https://theconversation.com/more-bad-news-for-dinosaurs-chicxulub-meteorite-impact-triggered-global-volcanic-eruptions-on-the-ocean-floor-91053">last year</a> – suggesting a connection between the asteroid impact, increased volcanic eruptions, and the mass extinction event.</p>
<h2>Sudden impact</h2>
<p>Back in 1980, the American experimental physicist <a href="https://www.britannica.com/biography/Luis-Alvarez">Luis Alvarez</a>, his geologist son <a href="http://eps.berkeley.edu/people/walter-alvarez">Walter</a> and their colleagues published an <a href="http://science.sciencemag.org/content/208/4448/1095" title="Extraterrestrial Cause for the Cretaceous-Tertiary Extinction">influential paper in the journal Science</a>.</p>
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Read more:
<a href="https://theconversation.com/life-quickly-finds-a-way-the-surprisingly-swift-end-to-evolutions-big-bang-110984">Life quickly finds a way: the surprisingly swift end to evolution's big bang</a>
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<p>In it, they outlined evidence of a global catastrophe, buried in a layer spread all over the planet, about 66 million years ago.</p>
<p>They found high levels of iridium – a rare element in Earth’s crust, but common in meteorites. They found shocked quartz – grains of quartz with telltale fractures from the blast wave of the impact, as well as evidence of molten rock thrown out from the impact blast.</p>
<p>With the later <a href="https://doi.org/10.1130/0091-7613(1991)019%3C0867:CCAPCT%3E2.3.CO;2" title="Chicxulub Crater: A possible Cretaceous/Tertiary boundary impact crater on the Yucatán Peninsula, Mexico">discovery of the Chicxulub impact crater</a> on the Yucatan Peninsula, Mexico, the case seemed sealed.</p>
<p>The reign of the dinosaurs ended with a meteorite impact, marking the end of the Cretaceous, and start of the Paleogene period, called the K-Pg boundary.</p>
<h2>Was there something else?</h2>
<p>Yet within the Earth science community, discontent continued to simmer.</p>
<p>Two of the largest mass extinctions in the geological record both coincide with the largest exposed continental flood basalt events in the past 542 million years. They are the <a href="https://dx.doi.org/10.1126/sciadv.1500470" title="High-precision geochronology confirms voluminous magmatism before, during, and after Earth’s most severe extinction">end of the Permian 251 million years ago</a>, and – as today’s Science paper highlights – the dinosaur extinction at the end of the Cretaceous 66 million years ago. </p>
<p>The coincidence seems too great. </p>
<p>In understanding the link between flood volcanism, meteorite impacts and extinctions, timing is everything.</p>
<p>In the new Science paper, a team from the United States and India present some of the most precise dates yet for the enormous eruptions in India, in a unit known as the Deccan Traps - an enormous flood basalt province in Western India that covers more than 500,000km<sup>2</sup> and in places is more than 2km thick.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=615&fit=crop&dpr=1 600w, https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=615&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=615&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=773&fit=crop&dpr=1 754w, https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=773&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/260078/original/file-20190221-148533-7ku0xu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=773&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Map outlining exposed areas of the Deccan Traps in modern day India.</span>
<span class="attribution"><span class="source">Courtney Sprain</span></span>
</figcaption>
</figure>
<p>They found that the best date for the Chicxulub impact – at 66.052 million years ago – was within 50,000 years of the peak eruption period of the Deccan Traps, meaning that the impact, and the ramp-up in volcanism, were essentially simultaneous.</p>
<h2>A seismic connection</h2>
<p>A connection between an impact in the Caribbean and volcanism in the Indian Ocean may seem tenuous, but in planetary science these associations are not uncommon.</p>
<p>One dramatic example is the <a href="https://www.britannica.com/place/Caloris">Caloris Basin</a> on the planet Mercury – a 1,500km-wide structure from an earlier meteorite impact. </p>
<p>Antipodal (at the opposite side of the planet) to this is a bizarre, fractured landscape called the disrupted terrain, which formed from <a href="https://www.sciencedirect.com/science/article/pii/S0032063311002340">shock waves from the impact</a> at Caloris. </p>
<p>This forms a precedent of sorts - an impact can create geological changes at vast distances. But back on Earth 66 million years ago, Chicxulub and the Deccan Traps weren’t quite antipodal.</p>
<p>The Deccan Traps formed when that part of what is now India was roughly over present-day Reunion Island, a small French Island near Madagascar. This island is still volcanically active, and powered by the same mantle upwelling that caused the Deccan volcanism.</p>
<p>The Yucatan Peninsula, like much of the Americas, was significantly closer to Europe (see below). </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=457&fit=crop&dpr=1 600w, https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=457&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=457&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=574&fit=crop&dpr=1 754w, https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=574&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/259893/original/file-20190220-148545-1hadz9o.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=574&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Reconstruction of Earth’s plates at 66 million years ago. The stars show the position of the Deccan Traps near India, and Chicxulub impact in Mexico.</span>
<span class="attribution"><span class="source">Image created by C O'Neill using GPlates (Gplates.org)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>But that may not matter. It has long been argued, <a href="http://trn.lyellcollection.org/content/S2-5/3/601" title="On the Connexion of certain Volcanic Phenomena in South America; and on the Formation of Mountain Chains and Volcanos, as the Effect of the same Power by which Continents are elevated">since at least Charles Darwin in 1840</a>, that <a href="https://doi.org/10.1146/annurev.earth.34.031405.125125" title="SEISMIC TRIGGERING OF ERUPTIONS IN THE FAR FIELD: Volcanoes and Geysers">earthquakes may trigger eruptions</a>. </p>
<p>The mechanisms are not well understood. Suggestions range from bubble formation in magmas, to the development of fractures in the crust <a href="https://doi.org/10.1146/annurev.earth.34.031405.125125" title="SEISMIC TRIGGERING OF ERUPTIONS IN THE FAR FIELD: Volcanoes and Geysers">allowing magma to escape faster</a>.</p>
<p>It has been recognised, though, that despite their distance from earthquakes, some volcanoes are simply more sensitive to earthquake activity than others, particularly <a href="https://link.springer.com/article/10.1007/s00445-018-1232-2" title="Revisiting short-term earthquake triggered volcanism">very active volcanoes</a>. Few volcanic events were more active than the Deccan Traps.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/260110/original/file-20190221-120353-kz89ta.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Deccan Traps lava flows in Western Ghats, India.</span>
<span class="attribution"><span class="source">Courtney Sprain</span></span>
</figcaption>
</figure>
<h2>Increased volcanic activity</h2>
<p>At the same time as the Deccan volcanic ramp-up, the global mid-ocean ridge system in the Pacific and Indian Oceans seems to have <a href="https://dx.doi.org/10.1126/sciadv.aao2994" title="Anomalous K-Pg–aged seafloor attributed to impact-induced mid-ocean ridge magmatism">experienced increased activity</a>.</p>
<p>Formed when two plates move apart, ocean ridges form the most extensive volcanic system on the planet.</p>
<p><a href="https://dx.doi.org/10.1126/sciadv.aao2994" title="Anomalous K-Pg–aged seafloor attributed to impact-induced mid-ocean ridge magmatism">Analysis of global gravity</a> has indicated anomalously thick crust at the K-Pg boundary, formed due to excess volcanic activity. This effect is only seen in the fastestspreading, and thus most volcanically active, systems in the Pacific and Indian Oceans.</p>
<p>Together, these observations suggest a global pulse of volcanic input at the time of the Cretaceous mass extinction, driven by the shock wave of the Chicxulub impact.</p>
<h2>Wipeout</h2>
<p>Exactly how this perfect storm of natural disasters – an asteroid collision and increased volcanic activity – drove the mass extinction of so much life on Earth is unclear at the moment.</p>
<p>As Science paper’s first author, Courtney Sprain, a former UC Berkeley doctoral student now at the University of Liverpool, UK, puts it:</p>
<blockquote>
<p>Either the Deccan eruptions did not play a role - which we think unlikely - or a lot of climate-modifying gases were erupted during the lowest volume pulse of the eruptions.</p>
</blockquote>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-many-dinosaurs-in-total-lived-on-earth-during-all-periods-100460">Curious Kids: How many dinosaurs in total lived on Earth during all periods?</a>
</strong>
</em>
</p>
<hr>
<p>Volcanism can warm the Earth, due to eruption of greenhouse gases like methane and carbon-dioxide. It can, along with impacts, also cool the atmosphere by adding <a href="https://doi.org/10.1146/annurev.ea.16.050188.000445" title="Volcanic Winters">sulfur aerosols</a> or <a href="http://science.sciencemag.org/content/219/4582/287" title="Environmental Effects of an Impact-Generated Dust Cloud: Implications for the Cretaceous-Tertiary Extinctions">dust</a>, respectively. </p>
<p>Gases can also reach the atmosphere from magma stewing below the surface, even without eruptions.</p>
<p>It’s not precisely clear how all these combined to decimate terrestrial and marine ecosystems, but an accurate timeline of events is critical to unravelling these interactions.</p><img src="https://counter.theconversation.com/content/112134/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Craig O'Neill has received funding from the Australian Research Council.</span></em></p>More evidence that the asteroid hit on Earth that marked the end of the dinosaurs could have triggered a deadly increase in volcanic activity.Craig O'Neill, Director of the Macquarie Planetary Research Centre/Associate Professor in Geodynamics, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1004602018-08-08T02:37:31Z2018-08-08T02:37:31ZCurious Kids: How many dinosaurs in total lived on Earth during all periods?<figure><img src="https://images.theconversation.com/files/230839/original/file-20180807-160647-1xjf427.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">If you discovered a new type of dinosaur, what would you name it?</span> <span class="attribution"><span class="source">Mavis Wong CC-BY-ND</span></span></figcaption></figure><p><em>This is an article from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky! You might also like the podcast <a href="http://www.abc.net.au/kidslisten/imagine-this/">Imagine This</a>, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.</em></p>
<hr>
<blockquote>
<p><strong>Could you please tell me how many dinosaurs in total lived on Earth during all periods? - Viren, age 6, Scotch College, Victoria.</strong> </p>
</blockquote>
<hr>
<p>This is a really great question. </p>
<p>The short answer is we know of about 900 valid dinosaur species that existed. “Valid” means scientists know the dinosaur from enough of the skeleton bones to feel pretty sure that it differs from all other known dinosaurs. There are hundreds of others which have been named, but are not considered “valid” as they were not based on well-enough preserved fossils.</p>
<p>To give you the long answer, first I need to explain what a dinosaur is, and when they lived.</p>
<h2>What exactly is a dinosaur, anyway?</h2>
<p>Dinosaurs were a group of medium to large reptiles that lived between 235 million years ago and 66 million years ago. Not many people know this, but the main thing that makes a dinosaur a dinosaur is their foot structure; they have a special kind of ankle joint. Their feet bones are like that of a bird.</p>
<p>Dinosaurs lived during three periods of geological time - the Triassic period (which was 252-201 million years ago), the Jurassic period (about 201-145 million years ago) and the Cretaceous period (145-66 million years ago). These three periods together make up the Mesozoic Era.</p>
<p>Just how many dinosaurs in total lived on Earth during the Mesozoic era is impossible to answer. One <a href="https://geojournals.pgi.gov.pl/agp/article/view/9800">study</a> by a Polish scientist called Jerzy Trammer estimated that the total dinosaur combined weight was greater than all the mammals on Earth today, but their individual <em>numbers</em> were much lower than species of today’s living mammals. </p>
<p>Birds are descended from one group of dinosaurs called the predatory theropods. Theropods have hollow bones and three-toed limbs. Dinosaurs from the <em>Tyrannosaurus</em> are a type of predatory theropods. So, technically speaking, all living birds are “living dinosaurs”.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/230833/original/file-20180807-191019-1f8qbf8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/230833/original/file-20180807-191019-1f8qbf8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=266&fit=crop&dpr=1 600w, https://images.theconversation.com/files/230833/original/file-20180807-191019-1f8qbf8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=266&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/230833/original/file-20180807-191019-1f8qbf8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=266&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/230833/original/file-20180807-191019-1f8qbf8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=335&fit=crop&dpr=1 754w, https://images.theconversation.com/files/230833/original/file-20180807-191019-1f8qbf8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=335&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/230833/original/file-20180807-191019-1f8qbf8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=335&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tyrannosaurus rex.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/471399695?size=huge_jpg">www.shutterstock.com</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-will-the-universe-expand-forever-or-contract-in-a-big-crunch-96209">Curious Kids: will the universe expand forever, or contract in a big crunch?</a>
</strong>
</em>
</p>
<hr>
<h2>Discovering dinosaurs</h2>
<p><em>Megalosaurus</em> was one of the first dinosaurs to be properly studied. It lived in the Jurassic Period, about 160 million years ago. </p>
<p>The English scientist Richard Owen created the word “dinosaur” in 1842, meaning “terrible lizard” because at the time he thought they were similar looking to large lizards. Today, we know they are not lizards, but a totally different kind of reptile.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/231022/original/file-20180808-191019-3zo0mc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/231022/original/file-20180808-191019-3zo0mc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=431&fit=crop&dpr=1 600w, https://images.theconversation.com/files/231022/original/file-20180808-191019-3zo0mc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=431&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/231022/original/file-20180808-191019-3zo0mc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=431&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/231022/original/file-20180808-191019-3zo0mc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=542&fit=crop&dpr=1 754w, https://images.theconversation.com/files/231022/original/file-20180808-191019-3zo0mc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=542&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/231022/original/file-20180808-191019-3zo0mc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=542&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Megalosaurus.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/megalosaurus-side-profile-large-carnivorous-theropod-361997615?src=DwQB2JBfuayzKFzUTd5FRQ-1-32">from www.shutterstock.com</a></span>
</figcaption>
</figure>
<p>Each year scientists dig up more new dinosaurs and get to name them. About 50 new dinosaurs are named every year. </p>
<p>I discovered a new dinosaur based on one bone in the museum collection in Perth. It came from the Geraldton region in Western Australia. It is Australia’s only named Jurassic theropod. I named it <em>Ozraptor</em>, meaning “the Lizard of Aus”.</p>
<p>As the fossil record of life is vastly incomplete, we can only guess that many, many more species existed - but we might never find their fossil remains. </p>
<p>At least we know that many new dinosaurs will continue to be found as expeditions keep going out searching for them every year. Most of the world’s new dinosaurs are coming from China, Mongolia and South America.</p>
<p>I’m really glad you are interested in dinosaurs. Who knows - maybe one day you will be part of an expedition that discovers a new dinosaur. If you found a new dinosaur, what would you name it?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-birds-sing-98381">Curious Kids: Why do birds sing?</a>
</strong>
</em>
</p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. They can:</em></p>
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<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em>Please tell us your name, age, and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/100460/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Long receives funding from The Australian Research Council.</span></em></p>We know of about 900 valid dinosaur species that existed. ‘Valid’ means scientists know the dinosaur from enough of the skeleton bones to feel pretty sure that it differs from other known dinosaurs.John Long, Strategic Professor in Palaeontology, Flinders UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/973832018-06-06T11:12:08Z2018-06-06T11:12:08ZJurassic World: can we really resurrect a dinosaur?<figure><img src="https://images.theconversation.com/files/221532/original/file-20180604-175425-imacvr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Resurrecting dinosaurs might not be so easy.</span> <span class="attribution"><a class="source" href="https://pixabay.com/en/tyrannosaurus-rex-dinosaur-reptile-284554/">pixabay/azdude</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>This summer, the fifth instalment of the Jurassic Park franchise will be on the big screen, reinforcing a love of dinosaurs that has been with many of us
since childhood. There is something awe inspiring about the biggest, fiercest, and “deadest” creatures that have ever walked the planet. But the films have had an additional benefit – they have sparked an interest in dinosaur DNA. </p>
<p>The “Mr DNA” sequence in the original movie is a <a href="https://theconversation.com/sci-fi-and-jurassic-park-have-driven-research-scientists-say-42864">great piece of science communication</a> and the concept of extracting DNA from the bodies of “dino” blood-engorged mosquitoes is an outstanding piece of fiction. It is, however, just fiction.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/qUaFYzFFbBU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Jurassic Park’s solution for resurrecting dinosaurs.</span></figcaption>
</figure>
<p>Quite by chance, we’ve recently identified <a href="https://www.nature.com/articles/s41467-018-04267-9">the overall genomic structure</a> of dinosaurs. The genomic structure is the way that genes are arranged on chromosomes in each species. Although individual animals from the same species will have a different DNA sequence, the overall genomic structure is species-specific. </p>
<p>We began by working out the most likely genomic structure of the bird-turtle ancestor, before tracing any changes that occurred from then to the present day. This lineage includes the emergence of dinosaurs and pterosaurs ~240 million years ago, passing through the theropod dinosaurs (whose members include <em>T.rex</em> and <em>Velociraptor</em>) and ends with birds. </p>
<p>Despite us not making any claims to have extracted dino DNA, the question that seems to be on most people’s lips is “does this bring us closer to a real Jurassic Park?” The answer is an emphatic “no”, and here’s why.</p>
<p>First, the idea that there is intact dino DNA contained within blood-sucking insects preserved in amber just doesn’t add up. Prehistoric mosquitoes containing Dino blood have been found, but any dino DNA contained within them has long since degraded. Neanderthal and <a href="https://theconversation.com/could-resurrecting-mammoths-help-stop-arctic-emissions-95956">woolly mammoth DNA</a> has been successfully isolated, but dino DNA is just too old. The oldest DNA ever found is around one million years old, but for dino DNA we would need to go back at least 66m years, so realistically we’re not even close. </p>
<p>Second, even if we could extract dino DNA, it would be chopped up into millions of tiny pieces and we would have little clue as to how these pieces should be organised. It would be like trying to do the world’s hardest jigsaw puzzle with no idea what the picture looks like or whether there are any missing pieces. </p>
<p>In Jurassic Park, the scientists find these missing pieces and fill them with frog DNA, but this wouldn’t give you a dinosaur, it would give you a hybrid or a “frogosaur”. These bits of frog DNA could have all kinds of negative effects on the developing embryo. It would also be infinitely more sensible to use bird rather than frog DNA as they are more closely related (but it still wouldn’t work). </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/221805/original/file-20180605-119870-1p9d0s3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221805/original/file-20180605-119870-1p9d0s3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=384&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221805/original/file-20180605-119870-1p9d0s3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=384&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221805/original/file-20180605-119870-1p9d0s3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=384&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221805/original/file-20180605-119870-1p9d0s3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=482&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221805/original/file-20180605-119870-1p9d0s3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=482&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221805/original/file-20180605-119870-1p9d0s3.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=482&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A Velociraptor can’t be resurrected in a chicken egg.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Fred_Wierum_Velociraptor.png">Fred Wierum/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Third, the idea that all you need is a strand of DNA and, hey presto, you can recreate a whole animal is, again, science fiction. DNA is a starting point but the development of the animal inside the egg is an intricate “dance” of genes switching on and off at the right time with a series of environmental cues. </p>
<p>In short, you need the perfect dino egg and all the complex chemistry contained within it. In the book, they generate artificial eggs, in the films they use ostrich eggs. Neither would work, you can’t put chicken DNA inside an ostrich egg and hope to get a chicken (people have tried). The same would be true of a <em>Velociraptor</em>. </p>
<p>And this is before we even consider legislature, planning permission, protest groups and the effect on the ecosystem. </p>
<h2>So we can’t resurrect a dinosaur, but…</h2>
<p>Here’s the thing: dinosaurs never became extinct. Quite the contrary, they are among us right now. Birds did not evolve from dinosaurs, birds are not closely related to dinosaurs. Birds are dinosaurs. </p>
<p>Dinosaurs (including birds) are the survivors of at least four extinction events, emerging each time in more diverse, weird and wonderful forms. One key element of our paper is that we theorise that their ability to do this is facilitated by their genome structure. We discovered that birds and most non-avian dinosaurs had a lot of chromosomes (packages of DNA). Having so many allows animals to generate variation, the driver of natural selection. </p>
<p>Nevertheless, and it is a long shot, it may be possible in future to use Jurassic Park technology to help undo some of the harm that humans have caused. Mankind has seen the extinction of well-known avian dinosaurs such as the dodo and the passenger pigeon. Recovery of DNA that is a only few hundred years old from these birds is a far more realistic proposition. It may also be that eggs from closely related living species might just be good enough. In the right conditions we may be able to use them to resurrect some of these species from extinction. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/mammoth-cloning-the-ethics-16183">Mammoth cloning: the ethics</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/97383/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Darren Griffin receives funding from the Biotechnology and Biological Sciences Research Council . </span></em></p><p class="fine-print"><em><span>r.o'<a href="mailto:connor@kent.ac.uk">connor@kent.ac.uk</a> receives funding from the BBSRC. </span></em></p>Jurassic Park’s dinosaur DNA premise is not so simple in real lifeDarren Griffin, Professor of Genetics, University of KentRebecca O'Connor, Postdoctoral research associate, University of KentLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/910532018-02-07T19:00:46Z2018-02-07T19:00:46ZMore bad news for dinosaurs: Chicxulub meteorite impact triggered global volcanic eruptions on the ocean floor<figure><img src="https://images.theconversation.com/files/205347/original/file-20180207-74479-1ragczb.jpg?ixlib=rb-1.1.0&rect=229%2C0%2C4290%2C3149&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Seismic shockwaves after a meteorite’s collision could affect systems all over the planet.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/large-meteor-burning-glowing-hits-earths-488993764">solarseven/Shutterstock.com</a></span></figcaption></figure><p>The end of the Cretaceous period 66 million years ago was a rough time to be living on Earth.</p>
<p>Three global catastrophes occurred nearly simultaneously: The <a href="https://doi.org/10.1126/science.208.4448.1095">Chicxulub meteorite slammed</a> into what is now Mexico’s Yucatan Peninsula, the massive <a href="https://doi.org/10.1038/333843a0">Deccan Traps volcanic province in modern-day India erupted</a>, and some three-quarters of Earth’s plants and animals, including all non-avian dinosaurs, went extinct. The occurrence of these three events at the same time in our planet’s history has fueled a decades-long <a href="https://doi.org/10.1016/S1631-0713(03)00006-3">debate about causal links</a>. Either a large sequence of volcanic eruptions or an extraterrestrial impact could conceivably cause a mass extinction – but were they all somehow connected?</p>
<p>As Earth scientists, we have reason to believe that there may be another event to add to the list. <a href="http://advances.sciencemag.org/content/4/2/eaao2994">Our new research</a>, published in Science Advances, shows that the Chicxulub impact may have triggered additional volcanic activity far from the Deccan Traps – along tens of thousands of miles of undersea volcanic ridges that lie at the edges of tectonic plates. The meteorite impact caused large seismic waves that traveled around the globe and were apparently capable of flushing magma out of the mantle and into the oceanic crust. This would presumably be more bad news for the dinosaurs and other flora and fauna of the time.</p>
<h2>Ripple effects of seismic activity</h2>
<p>It is well known that seismic activity can trigger a variety of hydrologic phenomena, and sometimes even volcanic eruptions. In the aftermath of nearby large earthquakes, <a href="https://doi.org/10.1038/ncomms8597">dry streams can start flowing</a>, well levels can go up or down, and <a href="https://doi.org/10.1146/annurev.earth.34.031405.125125">geysers sometimes erupt</a>. Seismicity also sets off volcanic activity, but only when conditions are just right – it’s only about <a href="https://doi.org/10.1146/annurev.earth.34.031405.125125">0.4 percent of explosive volcanic eruptions</a> that might be triggered by large earthquakes.</p>
<p>So could the massive earthquake generated when the Chicxulub meteorite crashed into Earth be related to the ongoing eruptions in the Deccan Traps? This volcanic province covered much of India with lava flows in less than a million years. A University of California, Berkeley-led team of researchers (including one of us, Leif Karlstrom) <a href="https://doi.org/10.1130/B31167.1">revisited the possibility of a connection</a> between these two events.</p>
<p>The most recent efforts to date these eruptions have clearly shown that the <a href="https://doi.org/10.1126/science.aaa0118">Deccan Traps began spewing lava</a> before the meteorite impact and the mass extinction occurred. But the Berkeley-led study suggested that the <a href="https://doi.org/10.1126/science.aac7549">Chicxulub impact triggered a rapid increase in their eruption rate</a>. If true, all three events could conceivably be connected: The impact would be followed by accelerated volcanic activity that could contribute to the mass extinction.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/205141/original/file-20180206-88775-1vu003i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Underwater lava flows ooze out between tectonic plates, as at Axial Seamount, where it lies on top of older lavas.</span>
<span class="attribution"><span class="source">Bill Chadwick, Oregon State University, and ROV Jason, Woods Hole Oceanographic Institution</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Looking to the ocean floor</h2>
<p>If the triggering-by-impact hypothesis is right, we’d expect that other volcanic systems would have been set off as well.</p>
<p>At any given time, the vast majority of the volcanic activity on Earth isn’t occurring in continent-covering floods of magma or in explosions like at Mount St. Helens. It’s on the seafloor, where the tectonic plates are spreading apart. As the Earth’s crust splits, the mostly solid mantle layer rises to fill the space created. It melts as it decompresses on the way up.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=203&fit=crop&dpr=1 600w, https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=203&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=203&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=255&fit=crop&dpr=1 754w, https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=255&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/205132/original/file-20180206-88799-1rj8m9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=255&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Illustration of a mid-ocean ridge, with magma rising from the mantle and erupting through the crust at the boundary between tectonic plates.</span>
<span class="attribution"><span class="source">Background, E. Paul Oberlander, WHOI Graphic Services. Inset, Bill Chadwick, Oregon State University, and ROV Jason, Woods Hole Oceanographic Institution. Modified by Joseph Byrnes</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>This new magma percolates its way to the surface and fuels nearly continuous volcanic activity along what are known as <a href="https://en.wikipedia.org/wiki/Mid-ocean_ridge">mid-ocean ridges</a>. This process creates practically all of the crust on the bottom of the ocean. Since the <a href="http://www.earthbyte.org/Resources/agegrid2008.html">ages of the seafloor are relatively well-known</a>, it preserves a record of oceanic volcanic activity stretching back over 100 million years. This remarkable record of volcanic activity creates an opportunity to test the triggering hypothesis.</p>
<p><a href="http://advances.sciencemag.org/content/4/2/eaao2994">In our new study</a>, we used publicly available data sets to make a record of the structure of the seafloor stretching back 100 million years. Since better topographic maps exist for <a href="https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA02820">Mars</a> and <a href="https://sos.noaa.gov/datasets/venus-topography/">Venus</a> than do for the <a href="http://topex.ucsd.edu/marine_topo/">Earth’s seafloor on a global scale</a>, we were forced to use indirect methods to look for variations in seafloor structures.</p>
<p>Minute variations in the strength of gravity at different locations as measured by satellites <a href="http://topex.ucsd.edu/marine_grav/mar_grav.html">provide the requisite mapping tool</a>. Spots that have an excess amount of rock sitting on the seafloor, as you’d expect to result from accelerated volcanic activity, will have a slightly stronger measurement for Earth’s gravitational field.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=298&fit=crop&dpr=1 600w, https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=298&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=298&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=375&fit=crop&dpr=1 754w, https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=375&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/205133/original/file-20180206-88775-1s17005.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=375&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The time with the most small structural anomalies on the sea floor – indicating 8 percent more mass anomalies than on average – occurs at 66 million years ago and coincides with the age of the Chicxulub meteorite impact.</span>
<span class="attribution"><span class="source">Byrnes and Karlstrom, Sci. Adv. 2018;4: eaao2994</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We then inspected the record of these “gravity anomalies” to look for any changes to the structure of the seafloor that happened quickly. We found an unusual abundance of these small structural anomalies on the seafloor happened within 1 million years of the Chicxulub impact. The gravity anomalies are consistent with roughly 650 foot high piles of excess material lying on 66-million-year-old seafloor in the Indian and Pacific Oceans.</p>
<p>The total volume of excess material is difficult to pin down, because a large amount of magma could have been injected into the lower crust where it would have a weaker gravitational signature. But we estimate that around the time of the Chicxulub impact, on the order of 23,000 to 230,000 cubic miles of magma erupted out of the mid-ocean ridges, all over the globe. This is on par with the largest eruptive events in Earth’s 4.5-billion-year history, including the Deccan Traps.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=261&fit=crop&dpr=1 600w, https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=261&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=261&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=327&fit=crop&dpr=1 754w, https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=327&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/205136/original/file-20180206-88775-1h6n02.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=327&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Dots mark areas on the seafloor that show high rates of spreading at the time of the Chicxulub impact 66 million years ago. Colors indicate the maximum gravity anomaly within 2 degrees.</span>
<span class="attribution"><span class="source">Byrnes and Karlstrom, Sci. Adv. 2018;4: eaao2994</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Refining the picture</h2>
<p>Our observations suggest the following sequence of events at the end of the Cretaceous period. Just over 66 million years ago, the Deccan Traps start erupting – likely initiated by a plume of hot rock rising from the Earth’s core, similar in some ways to what’s happening beneath Hawaii or Yellowstone today, that impinged on the side of India’s tectonic plate. The mid-ocean ridges and dinosaurs continue their normal activity.</p>
<p>About 250,000 years later, Chicxulub hits off the coast of what will become Mexico. The impact causes a massive disruption to the Earth’s climate, injecting particles into the atmosphere that will eventually settle into <a href="https://doi.org/10.1126/science.1177265">a layer of clay found across the planet</a>. In the aftermath of impact, volcanic activity accelerates for perhaps tens to hundreds of thousands of years. The mid-ocean ridges erupt large volumes of magma, while the Deccan Traps eruptions flood lava across much of the Indian subcontinent. In the end, three-quarters of the Earth’s plant and animal species have disappeared; the only remaining dinosaurs are the feathered, flying variety, normally referred to as birds. </p>
<p>Now, the goal is to further refine our understanding of each event and their interactions. Was there enough mid-ocean ridge activity to contribute to the mass extinction, or was the triggered submarine volcanism merely a symptom of some more significant planetary ailment? Were other volcanic systems triggered by the Chicxulub impact? Which played a larger role in driving the extinction: the volcanism or the meteor?</p>
<p>What is clear is that this new research points to global-scale connections between catastrophes, a good reminder that events happening on the other side of the planet can have effects felt everywhere.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/8wy33t0U1DE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Massive eruption of magma may have contributed to mass extinction at the end of the Cretaceous.</span></figcaption>
</figure><img src="https://counter.theconversation.com/content/91053/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Leif Karlstrom receives funding from the National Science Foundation.</span></em></p><p class="fine-print"><em><span>Joseph Byrnes does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Research suggests a new threat to life on Earth from the meteorite’s crash: Via seismic waves, the impact triggered massive undersea eruptions, as big as any ever seen in our planet’s history.Leif Karlstrom, Assistant Professor of Earth Sciences, University of OregonJoseph Byrnes, Postdoctoral Associate of Earth Sciences, University of MinnesotaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/871092017-11-09T14:17:43Z2017-11-09T14:17:43ZDinosaurs could have avoided mass extinction if the killer asteroid had landed almost anywhere else<figure><img src="https://images.theconversation.com/files/193808/original/file-20171108-14177-b9ea8f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The decline of the dinosaurs, the rise of mammals and, ultimately, the origins of humans were even more unlikely than previously thought, according to new research. The huge asteroid collision that sparked this change in the Earth’s diversity was already a highly improbable roll of the celestial dice. But <a href="http://nature.com/articles/doi:10.1038/s41598-017-14199-x">a new study</a> suggests the mass extinction that followed it was only so severe because of where the asteroid struck.</p>
<p><a href="https://theconversation.com/did-a-burning-oil-spill-wipe-out-the-dinosaurs-62456">Scientists believe</a> the dinosaurs were largely wiped out 66m years ago when an asteroid collision released a huge dust and soot cloud that triggered global climate change. The researchers, from Tohoku University in Japan, claim that the soot necessary for such a global catastrophe could only have come from a direct impact on rocks especially rich in hydrocarbons.</p>
<p>Rocks like this would only have been found on about 13% of the Earth’s surface. Add to this the need for a liberal dose of toxic sulphurous compounds in the rocks, and the odds that an impact of the same size (an already astronomically rare event) would have such devastating consequences lengthen to just one in 100.</p>
<p>The impact crater created by the 10km-diameter asteroid is located close to Chicxulub on Mexico’s Yucatán peninsula, and was only identified as recently as 1991. Before then, it was hidden to scientists because it lay partly under a blanket of <a href="http://geology.geoscienceworld.org/content/19/9/867">sediment on the seabed</a>.</p>
<p>The underlying rocks were composed of gypsum (rich in sulphur) and also contained large reserves of hydrocarbons. Had the impact occurred a few hundred miles away, or indeed at most locations on the globe, then the consequences of the collision may have been vastly less severe. Terrestrial dinosaurs and many other groups may never have been driven to extinction, and their survival may have hindered or completely prevented the later spread of mammals – and, of course, humans. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=417&fit=crop&dpr=1 600w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=417&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=417&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=524&fit=crop&dpr=1 754w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=524&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/193811/original/file-20171108-14193-emn16n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=524&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Global blackout.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>The immediate blast and resulting shock and tidal waves would have killed much in their path no matter where the impact had occurred. Earthquakes and volcanic activity would have been triggered worldwide, and pieces of burning debris may have started <a href="http://onlinelibrary.wiley.com/doi/10.1002/jgrg.20018/full">extensive wildfires</a>. </p>
<p>But it’s unlikely this would have caused the global extinction of huge numbers of species. Such immediate effects were relatively short-lived, and the real damage, as the researchers show, probably came from fine particulate matter ejected high into the stratosphere. The worst culprit, they argue, would have been fine hydrocarbon soots. This new research claims that those catapulted into the upper atmosphere probably originated from rocks at the impact site rather than from forest fires. </p>
<p>Soot in the stratosphere could have simply blocked out the sun over a period of years, creating the equivalent of a <a href="http://www.pnas.org/content/114/36/E7415.full">nuclear winter</a>, shutting down photosynthesis and decimating ecosystems as a result. But the researchers argue that as well as general darkening, the effects upon climate were more varied, resulting in droughts towards the equator and more extreme cooling at mid to high latitudes. Sulphate aerosols would also have caused acid rain, altering ocean chemistry and stressing marine and terrestrial ecosystems alike.</p>
<p>The Tohoku scientists used global climate models to predict the size of these effects depending upon the geology of where the asteroid struck, as well as the volume and chemistry of the material thrown into the upper atmosphere. In most other locations, it wouldn’t have produced such devastating results. It seems that the Earth could not have been hit anywhere much worse.</p>
<h2>The next mass extinction</h2>
<p>All species inevitably go extinct and the history of life on Earth is one of constant turnover. Extinctions also occur at all scales, from the demise of individual species to what we call “mass events” that see 75% or more of species wiped out globally. There have been five such <a href="https://theconversation.com/five-mass-extinctions-and-what-we-can-learn-from-them-about-the-planet-today-79971">mass events</a> over the last half billion years, and we appear to be sleepwalking <a href="https://theconversation.com/which-species-will-survive-the-earths-sixth-mass-extinction-47893">into a sixth</a> of our own making thanks to pollution, habitat destruction and hunting.</p>
<p>The possibility of a future asteroid impact is also very real. NASA’s <a href="https://cneos.jpl.nasa.gov/">Near Earth Object Program</a> seeks to map out the trajectories of comets and asteroids that appear set to come close to the Earth. Plans are afoot to develop technologies capable of <a href="https://www.nasa.gov/feature/nasa-s-first-asteroid-deflection-mission-enters-next-design-phase">deflecting objects</a> on a collision course.</p>
<p>But in the meantime, this new research suggests that we should worry slightly less about the probable consequences of the next extraterrestrial disaster, focus our attention closer to home, and reflect on our outrageous good fortune for being here in the first place.</p><img src="https://counter.theconversation.com/content/87109/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Wills has received or currently receives funding from BBSRC, NERC, The Leverhulme Trust and the John Templeton Foundation.</span></em></p>The mass extinction of the dinosaurs was down to the location of the asteroid’s impact and the kind of rocks it landed on.Matthew Wills, Professor of Evolutionary Palaeobiology at the Milner Centre for Evolution, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/726292017-02-27T13:41:56Z2017-02-27T13:41:56ZThe evidence that shows dinosaurs were in decline for 40 million years before the asteroid hit<figure><img src="https://images.theconversation.com/files/158136/original/image-20170223-32729-rf681f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The end was nigh.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/3d-illustration-brontosaurs-looking-upon-meteors-408550594?src=nBYOFRL9VULXHjReGGp5sg-1-6">Shutterstock</a></span></figcaption></figure><p>When the dinosaurs were wiped off the face of the planet, how did they leave? Was it a slow, plodding decline or a short sharp bang? Back in the 1960s and 1970s, debate about this question was mainly taking place on the ground, at <a href="https://yalealumnimagazine.com/articles/3921-the-man-who-saved-the-dinosaurs">fossil sites in places like Montana</a>. Paleontologist <a href="http://www.nytimes.com/1985/10/29/science/dinosaur-experts-resist-meteor-extinction-idea.html?pagewanted=all">Robert Sloan</a> and his colleagues documented evidence for the long-term decline of dinosaurs over a 10m to 20m-year period. Dinosaurs had been losing out, ever so slowly, to the rising mammals, mainly as a result of cooling climates.</p>
<p>Indeed, climates at this time were cooling. And because dinosaurs relied on the external environment to maintain their body temperatures, this would have hurt them. </p>
<p>But two revelations dramatically switched the consensus against gradual decline. First, the geological field evidence <a href="http://geology.geoscienceworld.org/content/23/10/881">suggested no gradual decline</a> in dinosaur fossils in the rocks. Plus the overlap of declining dinosaurs and rising mammals noted by Sloan turned out to be based on faulty fieldwork and fossil dating. Fossils can be moved from one type of rock to another by being “reworked” or eroded, moved along and then deposited for a second time in younger rocks, providing misleading information about their true age.</p>
<p>The other revelation was the <a href="https://theconversation.com/how-does-an-invisible-underwater-crater-prove-an-asteroid-killed-the-dinosaurs-57711">1980 discovery by Luis Alvarez</a>, which showed that the Earth had been <a href="https://theconversation.com/revealed-asteroid-that-killed-the-dinosaurs-boiled-earths-atmosphere-36606">struck by a huge meteorite</a> 66m years ago. It was a collision that threw up vast tonnages of black dust into the atmosphere, which blacked out the sun, leading to freezing and darkness for some months. This was accepted reluctantly at first by geologists, but then enthusiastically as the <a href="http://www.livescience.com/26933-chicxulub-cosmic-impact-dinosaurs.html">evidence accumulated</a>. </p>
<p>Impact and sudden death of the dinosaurs made complete sense. The last dinosaurs, such as <em>Triceratops</em> and <em>Tyrannosaurus rex</em>, were imagined as dumbfounded by the asteroid streaking through the sky, and killed wholesale by a consequent fireball and then freezing darkness.</p>
<p>But did the dinosaurs really disappear with a bang? <a href="http://research-information.bristol.ac.uk/files/70584653/Sakamoto_et_al._2016._PNAS_final_submitted_ver.pdf">New evidence</a> now suggests instead a very, very, long decline, perhaps as long as 40m years. Part of this comes from <a href="http://research-information.bristol.ac.uk/files/70584653/Sakamoto_et_al._2016._PNAS_final_submitted_ver.pdf">our application</a> of a modelling technique to the data. The key here is to have an evolutionary tree, what is known as a “phylogeny”, which is dated accurately against geological time. Although the fossil record of dinosaurs is incomplete and patchy, we do have high quality phylogenies, tested over <a href="http://www.nature.com/subjects/phylogenetics">30 years of research</a>, that provide solid information on dinosaurian relationships. </p>
<p>Once you have a phylogeny, and date it against a geological time scale, you can read off a great deal of new information. It helps to joins the dots, linking isolated finds, and bridging gaps. It also provides a framework from which rich data on rates of evolution can be calculated.</p>
<p>We wanted to explore a hint of decline that had been noted in the first such comparative <a href="https://issuu.com/felipeelias/docs/lloyd-et-al--2008">phylogenetic analysis</a>.<a href="http://www.pnas.org/content/113/18/5036">Our new work</a> focused on exploring the diversity dynamics of dinosaurs through their entire evolution. We confirmed first that they did most of their evolving in the first half of their reign on Earth, during the late <a href="http://www.bbc.co.uk/nature/history_of_the_earth/Triassic">Triassic</a> and early to middle <a href="http://www.bbc.co.uk/nature/history_of_the_earth/Jurassic">Jurassic</a> periods, some 230m to 150m years ago. </p>
<h2>Decline and fall</h2>
<p>Most importantly, we found clear evidence for a long-term decline from 40m years before the end of the <a href="http://www.bbc.co.uk/nature/history_of_the_earth/Cretaceous">Cretaceous</a> period. We looked at all dinosaurs, and then each of the main subgroups. The only exceptions were the duck-billed dinosaurs (hadrosaurs) and the horned ceratopsians, both of which showed renewed bursts of evolving into new distinct species later on.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/JqGphEaJvDE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
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<p>So after so much recent disagreement, can our <a href="http://research-information.bristol.ac.uk/files/70584653/Sakamoto_et_al._2016._PNAS_final_submitted_ver.pdf">new theory</a> be believed? We believe so. It is based on the most detailed data ever assembled, a complete evolutionary tree of more than 600 species of dinosaurs, with better control on the time scale than ever before. </p>
<p>The result was obtained through modelling of the data using an approach which allowed us to repeat the calculations millions of time, using different assumptions about uncertainties each time, to see whether the analysis converged on a single result. In this case, we modelled uncertainties in the phylogeny, in geological dating, and in sampling, and tried every variant of the data, and the result was robust. We can now say categorically: for their final 40m years on Earth, the dinosaurs were in decline - their rate of species extinction was on average consistently higher than their rate of forming new and distinct species (speciation).</p>
<p>But what we cannot yet explain is why this was so. We <a href="http://research-information.bristol.ac.uk/files/70584653/Sakamoto_et_al._2016._PNAS_final_submitted_ver.pdf">found correlation</a> of our speciation dynamics data with sea level, but a more detailed exploration is needed of the impact of cooling climates and their interactions with other species such as mammals. Whatever the driver, dinosaurs were declining. They went out with a long, protracted whimper … followed by that almighty meteoric bang.</p><img src="https://counter.theconversation.com/content/72629/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael J. Benton does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Their days were numbered for quite some time …Michael J. Benton, Professor of Vertebrate Palaeontology, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/624562016-07-14T13:07:00Z2016-07-14T13:07:00ZDid a burning oil spill wipe out the dinosaurs?<figure><img src="https://images.theconversation.com/files/130445/original/image-20160713-12380-s7artn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Sixty six million years ago, the dinosaurs suddenly disappeared, along with most of the species on the planet. The extinction occurred at precisely the same time that a giant asteroid struck the Earth. The fact that the two events happened at the same time makes it all but certain that <a href="https://theconversation.com/how-does-an-invisible-underwater-crater-prove-an-asteroid-killed-the-dinosaurs-57711">the asteroid wiped out the dinosaurs</a>, but just how did that extinction happen? Was it dust, shot into the sky, blocking out the sun? Acid rain produced by sulphur vaporised during the impact? <a href="https://theconversation.com/revealed-asteroid-that-killed-the-dinosaurs-boiled-earths-atmosphere-36606">An inferno</a> of hot debris?</p>
<p><a href="http://nature.com/articles/doi:10.1038/srep28427">A new study</a> may get us closer to solving this mystery. The asteroid struck the Yucatan Peninsula, a region with vast quantities of crude oil buried underground. New data shows that the burning of the oil produced billions of tons of soot, enough to dim the sun for years and lead to a decade of global cooling.</p>
<p>The Cretaceous-Paleogene (K-Pg) extinction event was severe, wiping out over 75% of all species, including <a href="http://onlinelibrary.wiley.com/doi/10.1111/jeb.12882/abstract">not just dinosaurs</a> but also many <a href="http://www.pnas.org/content/108/37/15253.full.pdf">birds</a>, <a href="http://www.smithsonianmag.com/smart-news/event-wiped-out-dinosaurs-nearly-did-mammals-well-180959521/?no-ist">mammals</a>, snakes, <a href="http://www.livescience.com/25392-lizards-killed-dinosaur-extinction.html">lizards</a>, plants, and even insects. It was global, hitting all continents and all oceans. And it was rapid, with species seeming to vanish overnight.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/130446/original/image-20160713-12353-103qlvv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/130446/original/image-20160713-12353-103qlvv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/130446/original/image-20160713-12353-103qlvv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/130446/original/image-20160713-12353-103qlvv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/130446/original/image-20160713-12353-103qlvv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=564&fit=crop&dpr=1 754w, https://images.theconversation.com/files/130446/original/image-20160713-12353-103qlvv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=564&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/130446/original/image-20160713-12353-103qlvv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=564&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Deep impact.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>In 1979, physicist Luis Alvarez was trying to figure out just how much time the extinction took. He focused on a thin layer of clay – the K-Pg boundary – that marked the extinction. His clever idea was to look at iridium levels in the boundary clay. Iridium is a rare metal found primarily in meteorites, so the slow trickle of iridium from meteorites burning up in the atmosphere should act as a sort of cosmic hourglass, telling the passing of time.</p>
<p>His plan backfired spectacularly: iridium levels in the clay were orders of magnitude above the normal background levels. The K-Pg boundary was the <a href="http://earthscience.rice.edu/wp-content/uploads/2015/11/Alvarez_K-Timpact_Science80.pdf">debris of a giant asteroid</a> impact. A few calculations suggested that it would take an asteroid 10 kilometres across to produce all that iridium. The idea that an asteroid wiped out the dinosaurs was widely ridiculed – but then, in 1990, the giant Chicxulub crater in Mexico <a href="https://pangea.stanford.edu/courses/ges57/pdf/chicxulub_hildebrand.pdf">was discovered</a>.</p>
<h2>Global extinction</h2>
<p>But how does an asteroid impact in Mexico cause a worldwide extinction? Alvarez read about the <a href="http://www.smithsonianmag.com/history/blast-from-the-past-65102374/?no-ist">1815 explosion of Tamboro</a>. Sulphate gas shot into the atmosphere caused a volcanic haze that reflected sunlight. It lead to the “<a href="http://science.sciencemag.org/content/224/4654/1191">Year Without a Summer</a>”, when freezing temperatures in summer lead to widespread crop failures and famine. Alvarez proposed that debris from Chicxulub had blocked out the sun. Without the sun, plants and plankton couldn’t make food and the entire ecosystem starved.</p>
<p>It was a clever idea but studies of the K-Pg boundary revealed a problem. The debris was mostly coarse and would have dropped out out of the sky in a matter of a few months or weeks – <a href="http://geology.gsapubs.org/content/30/2/99.short">not long enough</a> to starve giant dinosaurs. There wasn’t enough fine debris that could stay aloft for years to cause an extinction. So what did?</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/130536/original/image-20160714-23336-1irskk1.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/130536/original/image-20160714-23336-1irskk1.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=341&fit=crop&dpr=1 600w, https://images.theconversation.com/files/130536/original/image-20160714-23336-1irskk1.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=341&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/130536/original/image-20160714-23336-1irskk1.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=341&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/130536/original/image-20160714-23336-1irskk1.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=428&fit=crop&dpr=1 754w, https://images.theconversation.com/files/130536/original/image-20160714-23336-1irskk1.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=428&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/130536/original/image-20160714-23336-1irskk1.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=428&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Oil field on fire.</span>
<span class="attribution"><span class="source">Jonas Jordan/Wikimedia Commons</span></span>
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</figure>
<p><a href="http://nature.com/articles/doi:10.1038/srep28427">A new study</a> by Kunio Kaiho and colleagues published in the journal Scientific Reports suggests a possible explanation. The K-Pg boundary contains soot. Although originally thought to be produced by wildfires, studies of its chemistry suggest that it is actually derived from burning hydrocarbons (crude oil). This fact seems puzzling until you consider that the Gulf of Mexico contains vast oil reserves. The Jurassic Cantarell oil field, the largest in Mexico, is nearby and, in fact, the Chicxulub crater was only discovered because geologists were mapping the area in search of oil. </p>
<p>As the Chicxulub asteroid tore into the earth, it released the oil locked in the rock. The Deepwater Horizon spill produced <a href="http://www.uscg.mil/foia/docs/dwh/fosc_dwh_report.pdf">4.9 million barrels</a> of oil from just a tiny hole in the ocean floor. The Chicxulub crater was 180 kilometers across. The intense heat of the impact would have burned the oil to create clouds of black soot and shot them into the stratosphere. Critically, tiny soot particles can stay up in the atmosphere for years. But was there enough to block out the sun?</p>
<p>The researchers from Tohoku University in Japan studied the chemistry of soot at the K-Pg boundary and then estimated the amount of soot produced by impact. The total burned carbon produced was on the order of 1.8 to 60 billion tons.</p>
<h2>Dark and cold</h2>
<p>They then used computer models to estimate the effects on the climate. Their models showed that the soot would have been highly effective in blocking light. Depending on the amount of soot, sunlight would have been reduced by 50% to 90%, and the global temperature would have cooled by between 6°C and 18°C, with cooling being especially severe towards the poles. Cooler temperatures would have also reduced rainfall, leading to widespread drought.</p>
<p>Critically, the soot cloud would stay aloft for years. The darkness and cooling were most severe in the first few years, but it would have taken a decade for light levels to slowly return to normal, and even longer for the climate to return to normal.</p>
<p>The research also helps put a time limit on the dinosaur extinction, suggesting the bulk of it took place in a span of less than ten years. </p>
<p>It’s probably too soon to say that we have definitively solved the extinction puzzle. Science is rarely that neat and tidy. The nature of science is that, at best, we need to run more analyses and collect more data to confirm new finds, and at worst, it’s full of seemingly promising dead ends.</p>
<p>But the new study is one of the most exciting developments in years, and it suggests that we may be closer to finally understanding the extinction of the dinosaurs. It may be that their extinction was caused by pollution and climate change caused by burning oil.</p>
<p>This could also explain why other asteroid impacts aren’t associated with mass extinctions. It may have been the unlucky coincidence of a huge oil field and a giant asteroid impact that made Chicxulub so deadly. And there is a certain irony in the possibility that the same oil that did in the dinosaurs is now being used to run our own civilization – and perhaps threatening it as well.</p><img src="https://counter.theconversation.com/content/62456/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas R. Longrich does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New research suggests the Chicxulub asteroid impact threw up billions of tons of oil soot that blocked out the sun for a decade.Nicholas R. Longrich, Senior lecturer, palaeontology, Milner Centre for Evolution, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/590312016-06-23T10:15:49Z2016-06-23T10:15:49ZThe top six dinosaur myths and how we busted them<figure><img src="https://images.theconversation.com/files/126953/original/image-20160616-15075-fw6p32.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/simononly/3102566739/in/photolist-5JasZZ-5Jasni-5JeGA7-5JeHkE-5JeMrd-5JeKDu-8XLHbg-dxYRRr-bPDhJR-GCbRm-naAYiS-5Jas7D-5JatCp-nsT9Pb-5JeJL5-c9cFQu-ntDiv1-5bkhcK-oUpnWK-c8VaDL-86fwzd-w1oPr-89gohr-89gniX-89gmQe-89goBk-5P6kkD-89jDi3-6UrJQ4-56iw7F-5P6ofZ-5PaBJJ-6EbCp5-5PaAsC-8rV4CN-6E7A54-br75d-89gnPv-6EbBnJ-n9X2e9-ed4eNY-5P6nGZ-6E7xHF-f3iBBA-5P6kQe-6E7FZT-89gprT-6EbMpu-FGzva-5bpuJ7">Simo Q/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>When the first dinosaur bone <a href="http://www.oum.ox.ac.uk/learning/pdfs/plot.pdf">was described in 1676</a>, it was thought to come from an elephant or perhaps a giant. Over a century later, scientists realised such fossils came from a creature they named Megalosaurus, portrayed as a sort of stocky, overgrown lizard. Then, in 1842, leading anatomist Richard Owen recognised Megalosaurus as part of a whole new group of animals, which he named Dinosauria, or “Terrible Lizards”.</p>
<p>Since then, around 700 different dinosaur species have been described, with <a href="http://www.pnas.org/content/113/13/3447">more found</a> <a href="http://www.bioone.org/doi/full/10.17161/paleo.1808.18764">every</a> <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0151661">month</a>. Our ideas about dinosaurs have also changed radically. The dinosaurs we know today are very different from the ones in the books you may have read as a child. </p>
<h2>Myth 1: Dinosaurs were all big</h2>
<p>The name dinosaur tends to evoke images of giants – and certainly many were very large. <em>Tyrannosaurus rex</em> was around 12 metres long and weighed more than five tonnes, the size of an elephant, and it probably wasn’t even the <a href="http://www.tandfonline.com/doi/abs/10.1671/0272-4634%282007%2927%5B108%3AMTIBTY%5D2.0.CO%3B2#.V07Sy2Nlmi5">biggest carnivore</a>. Long-necked, plant-eating sauropods grew to titanic proportions. The enormous <em>Argentinosaurus</em> is known from just a few bones, but its size has been estimated at 30 metres in length and <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0078733">80 tonnes in weight</a>. That’s larger than any living land mammal and all but the largest whales. And dinosaurs are unique here. No other group of land animals before or since was able to grow as large.</p>
<p>But not all dinosaurs were giants. The horned dinosaur <a href="https://theconversation.com/how-i-found-a-small-weird-looking-horned-dinosaur-from-eastern-usa-51375"><em>Protoceratops</em></a> was the size of a sheep. <em>Velociraptor</em> was the size of a golden retriever and had to be scaled up for <a href="https://www.theguardian.com/science/2009/feb/08/jurassic-park-dinosaur-inaccuracies">Jurassic Park</a> to make it more terrifying. Recent years have seen an explosion in the number of small species discovered, such as the<br>
<a href="http://www.pnas.org/content/early/2009/03/13/0811664106">cat-sized raptor </a><em>Hesperonychus</em>, the <a href="http://www.telegraph.co.uk/news/science/dinosaurs/5012159/Feathered-dinosaur-throws-bird-evolution-into-a-flap.html">rabbit-sized plant-eater <em>Tianyulong</em></a>, and the quail-sized insect-eater <a href="https://www.researchgate.net/publication/270218031_A_New_Specimen_of_Shuvuuia_Deserti_Chiappe_et_al_1998_from_the_Mongolian_Late_Cretaceous_with_a_Discussion_of_the_Relationship_of_Alvarezsaurids_to_Other_Theropod_Dinosaurs"><em>Parvicursor</em></a>. The smaller species were probably more common than their giant cousins. It’s just that the massive bones of a <em>T. rex</em> are more likely to have been preserved and a lot easier to spot in the field. </p>
<h2>Myth 2: Dinosaurs were all scaly</h2>
<p>When dinosaurs were first discovered, it seemed obvious that because they were related to crocodiles and lizards, they must have been scaly. And many dinosaurs – including duckbills, horned dinosaurs, sauropods, and armoured dinosaurs – do <a href="https://www.theguardian.com/science/2015/jun/03/most-dinosaurs-had-scales-not-feathers-fossil-analysis-concludes">preserve scale impressions</a>. But in the 1970s, palaeontologists began wondering if some dinosaurs might have been feathered, like their bird relatives. </p>
<p>This was considered wild speculation at the time, but in 1997 a small carnivorous dinosaur <a href="http://www.nature.com/nature/journal/v391/n6663/abs/391147a0.html">named <em>Sinosauropteryx</em></a> was found to be covered not with scales, but a soft, fuzzy down. Since then, feathers have been discovered on the plant-eating ornithopods, fanged heterodontosaurs, and many families of carnivorous dinosaurs <a href="http://www.wired.com/2012/04/yutyrannus-huali-feathers/">including Tyrannosauridae</a>- meaning that <em>T. rex</em> was probably covered in feathers, not scales. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/126954/original/image-20160616-15115-2wx6yd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/126954/original/image-20160616-15115-2wx6yd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/126954/original/image-20160616-15115-2wx6yd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/126954/original/image-20160616-15115-2wx6yd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/126954/original/image-20160616-15115-2wx6yd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/126954/original/image-20160616-15115-2wx6yd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/126954/original/image-20160616-15115-2wx6yd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Soft and fuzzy.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/agude/3580099946/in/photolist-6smWZ9-8cLRaj-9vZ99q-dKdNzJ-svkuWP-sfbPbv-dK8ndT-9KTYCi-dK8jFH-dKdMfu-pucZsJ-o5oCpH-dKdP7Q-dKdPJu-ptKAG4-pcx6m9-dKdN8d-3qLck-9TW5A-mM5bfe-7KHoYq-5BAeH9-bg13nF-HELK9-gtCyxK-p9dUUi-9nQuSu-Gizp3v-poLUHY-5pDYDP-fcMK46-pJHGr5-dK8ifM-7Db4YS-dKdQ4w-dK8k2a-fd33yJ-poEea1-p9f2Yu-p9fw7S-pLrRRY-poMs1C-dCsWi9-pqGruS-pqHizS-dK8kkF-pqG86a-pEY5wC-9KWxE3-pJAwKP">A Gude/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Myth 3: Dinosaurs were all green and brown</h2>
<p>Early paintings of dinosaurs favoured a drab palette, with monotone animals dressed in depressing shades of <a href="http://www.charlesrknight.com/Enlarge.htm?109">grey, green, and brown</a>. If the Mesozoic era really was that dreary, no wonder they went extinct. But in reality the colours would have been much more vibrant, even garish. Studies of dinosaur scales and feathers have revealed traces of melanin, the same pigment that lends colour to lizard scales, bird feathers and our hair. Analyses show that dinosaurs came in a wide variety of colours including black, white, <a href="http://news.bbc.co.uk/1/hi/sci/tech/8481448.stm">and ginger</a>. A few show-offs even had an <a href="http://www.smithsonianmag.com/science-nature/microraptor-was-a-glossy-dinosaur-119691559/">iridescent sheen</a> to their feathers.</p>
<p>Not only that, but many dinosaurs were boldly patterned with <a href="http://news.nationalgeographic.com/news/2010/01/photogalleries/100127-new-dinosaur-colors-feathers-nature-pictures/">spots and stripes</a>, white bellies and dark backs. Some of these patterns probably evolved as camouflage, to help dinosaurs hide from predators and prey. But bright colours and conspicuous patterns would have served to draw the eye of potential mates, much like the tail of a peacock.</p>
<h2>Myth 4: Dinosaurs were bad parents</h2>
<p>Most reptiles simply bury their eggs and walk away, leaving their offspring to fend for themselves as best they can. This hands-off parenting is risky. A sea turtle must lay thousands of eggs over its lifespan to see a few grow up. Dinosaurs were once thought to use the same “lay ‘em and leave ‘em” strategy. We now know that’s wrong.</p>
<p>Living dinosaur relatives – birds and crocodiles – guard their eggs and their young, so it’s a reasonable assumption that the dinosaurs did as well. And there’s now evidence of this. When expeditions to the Gobi Desert found a dinosaur atop a clutch of eggs, it was assumed to have died while plundering the nest. It was named <a href="http://digitallibrary.amnh.org/bitstream/handle/2246/3223/?sequence=1"><em>Oviraptor</em>, or “egg thief”</a>. But then more skeletons were found atop clutches of eggs, <a href="https://www.newscientist.com/article/dn26970-stunning-fossils-big-mama-brooding/">sitting on them like brooding birds</a>. It turns out <em>Oviraptor</em> didn’t eat eggs —- it was guarding them. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/126958/original/image-20160616-15101-ttgdtl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/126958/original/image-20160616-15101-ttgdtl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/126958/original/image-20160616-15101-ttgdtl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/126958/original/image-20160616-15101-ttgdtl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/126958/original/image-20160616-15101-ttgdtl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/126958/original/image-20160616-15101-ttgdtl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/126958/original/image-20160616-15101-ttgdtl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">We can go to the gift shop after you’ve eaten.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/yaketyyakyak/7001647988/in/photolist-bEHh1L-bEHhpw-bEHiSQ-bTC7UF-bTC39F-bY3NQG-bTC86F-bTC3Vx-bY3KEJ-bEHk9N-bEHonN-bY3R1C-f6YWqs-bEHmUq-8PCwt2-5fdD8B-dEvExP-deHGN5-5LvgkH-4d1Vo5-4gbYEp-5gx5bk-kdaFT-98uVr3-p8dB6q-8onrLx-bprGsC-dEvHnD-54uRgP-bTC71p-bTC6EZ-bY3ZSy-7cLYfc-efw3DE-dEB58Y-8CnLu2-bEHj9b-bY3LTC-98rKsg-bEHk2h-bEHnRy-bTC8c6-dEvUn6-bTC5Ti-bTC3Tn-dfzWt7-bTC1WB-X6aXz-bTC5av-bTC22r">Dave Catchpole/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Myth 5: Dinosaurs were doomed to extinction</h2>
<p>Dinosaur extinction was long blamed on some failure of the dinosaurs themselves, a failure to adapt to the changing environment. In reality, dinosaurs were diverse for more than 100m years with fossils found in North and South America, Asia, Europe, Africa, and even Antarctica.</p>
<p>Although some argue this diversity <a href="http://www.bbc.co.uk/news/science-environment-36073592">was in decline</a>, the fossils show that dinosaurs remained widespread, common and diverse until 66m years ago, when an <a href="https://theconversation.com/how-does-an-invisible-underwater-crater-prove-an-asteroid-killed-the-dinosaurs-57711">asteroid struck</a> the Earth in what is now Mexico. Debris from the impact blocked out the sun and plunged the world into darkness. The disappearance of the dinosaurs wasn’t fated – it was a cosmic accident. If the asteroid had deviated by a fraction of a fraction of a degree, dinosaurs would still rule the planet – and we wouldn’t. </p>
<h2>Myth 6: Dinosaurs all became extinct</h2>
<p>The asteroid wiped out the dinosaurs, almost. <em>T. rex</em>, <em>Triceratops</em> and the rest disappeared, but a handful of small feathered dinosaurs, probably less than a dozen species, survived. They were birds — small, flying cousins of <em>T. rex</em> and <em>Velociraptor</em> and the direct descendants of the carnivorous dinosaurs. And they not only survived but thrived, <a href="http://news.nationalgeographic.com/news/2014/12/141211-bird-crocodile-dinosaur-genome-evolution-science/">evolving into</a> some ten thousand species of birds.</p><img src="https://counter.theconversation.com/content/59031/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nicholas R. Longrich does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Think you know all about the dinosaurs? You might be surprised.Nicholas R. Longrich, Senior lecturer, palaeontology, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/607112016-06-08T15:58:08Z2016-06-08T15:58:08ZFossil teeth reveal the secret rise of mammals – millions of years before dinosaurs became extinct<figure><img src="https://images.theconversation.com/files/125700/original/image-20160608-3475-zhgazj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Early mammal _Purgatorius unio_</span> <span class="attribution"><span class="source">Nobu Tamura</span></span></figcaption></figure><p>What would have happened if an asteroid hadn’t killed the dinosaurs? Perhaps mammals wouldn’t have evolved to become the planet’s dominant group of animals and humans would never have existed. We’re certainly used to the idea that it was only after the dinosaurs (apart from birds) became extinct around 66m years ago, that mammals were able to develop and spread around the globe. But new research suggests this picture of Earth’s evolution may not be completely accurate.</p>
<p>Work by a team that includes me and other palaeontologists from the universities of Chicago and Southampton has unveiled a <a href="http://rspb.royalsocietypublishing.org/content/283/1832/20160256">new level of detail</a> of early mammals. We discovered that the therian mammals (the kind that gave rise to most modern mammals) were actually beginning to diversify between 10m years and 20m years before the Cretaceous mass extinction event that wiped out the dinosaurs.</p>
<p>This finding reflects the considerable changes in our understanding of the early evolution of mammals, thanks to exceptional fossils found over the last few years. </p>
<p>Previously, most palaeontologists thought that mammal diversity was suppressed by the <a href="https://www.ucl.ac.uk/news/news-articles/1215/221215-mammal-diversity">dominance of dinosaurs</a>. This was largely based on the fact that many of the early mammal fossils that had been found were from small, insect-eating animals with very similar feeding habits and life histories. But with the help of some astounding new fossils, including several from China, we have shown that mammals at this time were much more diverse than this suggests.</p>
<p>We focused on studying several aspects of early mammal diversity, including the number of species through time and how these animals differed in both their physical structure and the way they lived. We also looked at how these things changed through time, particularly during the period either side of the extinction event. To do this, we studied the shape of teeth of hundreds of early mammal specimens in museum fossil collections.</p>
<h2>Greater diversity</h2>
<p>Mammal teeth are highly developed, with uniquely complicated series of cusps, troughs and pits that perform precise functions for feeding. This means the specific shape of teeth can offer a wealth of information on the lives of long-extinct animals.</p>
<p>Tracking changes in tooth shape through time showed us that the mammals that lived during the years leading up to the dinosaurs’ demise had widely varied diets. This also helped us uncover another surprising finding. Mammals with the most extreme tooth shapes disappeared immediately following the extinction, which suggests that those that had the most specialised diets suffered along with the dinosaurs.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/125738/original/image-20160608-3516-15ev253.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/125738/original/image-20160608-3516-15ev253.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/125738/original/image-20160608-3516-15ev253.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/125738/original/image-20160608-3516-15ev253.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/125738/original/image-20160608-3516-15ev253.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/125738/original/image-20160608-3516-15ev253.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/125738/original/image-20160608-3516-15ev253.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Answers in the teeth.</span>
<span class="attribution"><span class="source">Dave Grossnickle</span></span>
</figcaption>
</figure>
<p>Our research follows <a href="http://www.pnas.org/content/113/18/5036.abstract">other recent findings</a> that dinosaur diversity was already decreasing before the extinction event, exactly as mammals were on the rise. So what caused this growing change in the prehistoric animal kingdom? One explanation is that the rapid spread of flowering plants (angiosperms) during the late Cretaceous period had a <a href="http://www.nature.com/nature/journal/v483/n7390/abs/nature10880.html">significant effect</a> on the ecology of animal groups.</p>
<p>It is possible that mammals may have been able to adapt to this change in plant life and flourish while the dinosaurs could not. Small-bodied mammals may have been early adaptors to the range of new food sources (fruit and seeds), ecosystems and insect prey provided by the flowering plants. Meanwhile, <a href="http://bit.ly/22SKTpA">non-avian dinosaurs</a> felt more of the negative effects as these flowering plants took over their habitats, causing their traditional food sources to disappear.</p>
<h2>Mammals’ shaky start</h2>
<p>Another traditional theory that our research questions is that mammals <a href="https://www.ucl.ac.uk/news/news-articles/1215/221215-mammal-diversity">diversified rapidly</a> immediately after the dinosaurs went extinct. Traditionally, the extinction has been seen as an ideal opportunity for mammal evolution to take off, but our findings suggest that early mammals were also hit by a <a href="http://rspb.royalsocietypublishing.org/content/283/1832/20160256">selective extinction event</a>. Some that could live off of a wide variety of foods were able to survive, but many other mammals with specialised diets went extinct.</p>
<p>By offering a more realistic image of the dynamics of mass extinction on mammals, our research may also provide important evidence of how mammals <a href="https://www.sciencedaily.com/releases/2014/01/140122134234.htm">could be affected</a> by man-made climate change. It raises the question of whether we should prepare for a similar selective extinction event in modern mammals as occurred 66m years ago.</p>
<p>This highlights how studying the fossils of long-dead organisms can actually help us to model our own effects on global ecosystems and habitats. In a rapidly changing world, the fossil record is a unique and unadulterated constant that may provide solutions far beyond what most people expect.</p><img src="https://counter.theconversation.com/content/60711/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elis Newham receives funding from NERC, EPSRC. </span></em></p>New research reveals that mammals didn’t wait for the dinosaurs to die out before starting their rapid spread.Elis Newham, PhD candidate, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.