tag:theconversation.com,2011:/id/topics/triassic-7414/articlesTriassic – The Conversation2018-01-05T13:22:56Ztag:theconversation.com,2011:article/896882018-01-05T13:22:56Z2018-01-05T13:22:56ZDavid Attenborough’s Sea Dragon – and the science behind a tantalising prehistoric ‘murder mystery’<figure><img src="https://images.theconversation.com/files/200993/original/file-20180105-26145-1wickxb.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">How the fossilised creature may have looked in its heyday.
</span> <span class="attribution"><span class="source">BBC Pictures</span></span></figcaption></figure><p>Sea Dragon, you ask? It sounds as if David Attenborough has decided to change things up a bit and enter the world of Game of Thrones. But, not quite. <a href="http://www.bbc.co.uk/programmes/b09m2kgl">Attenborough and the Sea Dragon</a> – to be screened on January 7 – is a new, one-off BBC documentary presented by Sir David Attenborough, which tells the story of a newly discovered ichthyosaur from the Dorset coast, England.</p>
<p>The word “Sea Dragon” refers to two extinct types of reptiles, <a href="http://www.bbc.co.uk/nature/life/Ichthyosaur">ichthyosaurs</a> and <a href="http://www.bbc.co.uk/nature/life/Plesiosaur">plesiosaurs</a>. They were first brought to the attention of the scientific world in the early 19th century, and described and named in 1821. </p>
<p>The scientists were well aware that these were not actual dragons, of course, but some people (notably the early collector, Thomas Hawkins), thought the word “dragon” would help to popularise these incredible animals. Their discovery even predates the formal recognition of the word dinosaur, in 1842. </p>
<p>Indeed, these animals are not “swimming dinosaurs”, as they are commonly and mistakenly described as, but are an entirely different group of extinct reptiles that lived at the same time as the dinosaurs. They were a highly successful group that first appeared in the Early Triassic, around 248m years ago, and became extinct about 90m years ago, in the Late Cretaceous.</p>
<h2>On British shores</h2>
<p>Most of the early discoveries were found in the UK, having come from the early part of the Jurassic Period, from inland quarries in Somerset and from the coastal section of the Lyme Regis-Charmouth area, Dorset. The inspirational Victorian fossil hunter and palaeontologist, <a href="http://www.lymeregismuseum.co.uk/collection/mary-anning/">Mary Anning</a>, collected many ichthyosaur specimens from around Lyme Regis and Charmouth, including some of the first brought to the attention of geologists. </p>
<p>Such fossils captivated scientists and the general public, which led to interest from museums and institutions around the globe, eager to add a specimen to their collection. Remains are displayed and stored in museums around the globe. Today, there is still major interest in collecting and studying such specimens.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/200942/original/file-20180105-26154-pn6r09.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/200942/original/file-20180105-26154-pn6r09.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=378&fit=crop&dpr=1 600w, https://images.theconversation.com/files/200942/original/file-20180105-26154-pn6r09.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=378&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/200942/original/file-20180105-26154-pn6r09.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=378&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/200942/original/file-20180105-26154-pn6r09.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=475&fit=crop&dpr=1 754w, https://images.theconversation.com/files/200942/original/file-20180105-26154-pn6r09.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=475&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/200942/original/file-20180105-26154-pn6r09.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=475&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Partial skeleton of <em>Leptonectes moorei</em>, a species of ichthyosaur named after fossil collector Chris Moore. Held in the collections of the Natural History Museum, London.</span>
<span class="attribution"><span class="source">Natural History Museum, London</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>For most of my academic career, which spans just over a decade, I have been studying ichthyosaurs, with a key emphasis on those collected from the Early Jurassic rocks of Britain. Over the years, I have been through countless museum collections across the UK and elsewhere, in hope of examining as many British Early Jurassic ichthyosaurs as possible. In doing so, I’ve seen thousands of specimens, ranging from isolated bones to complete skeletons, and from pregnant individuals to specimens with their last meal preserved. It is hard to quantify the great number of specimens known, but I have probably seen (either physically, or as photos) more than 90% of all British Early Jurassic ichthyosaurs that are stored in museums and university collections.</p>
<p>Globally, there are 25 species of Early Jurassic ichthyosaurs known. I have named five of them: <a href="http://www.tandfonline.com/doi/abs/10.1080/02724634.2014.903260?journalCode=ujvp20"><em>Ichthyosaurus anningae</em></a>, <a href="http://www.tandfonline.com/doi/abs/10.1080/14772019.2016.1183149"><em>Wahlisaurus massarae</em></a>, <a href="http://onlinelibrary.wiley.com/doi/10.1002/spp2.1065/pdf"><em>Ichthyosaurus larkini</em> and <em>I. somersetensis</em></a>, and <a href="http://www.tandfonline.com/doi/abs/10.1080/02724634.2017.1361433?journalCode=ujvp20"><em>Protoichthyosaurus applebyi</em></a>. </p>
<p>Each of the new species were based on the (re)discovery of specimens already in museum collections – indeed, palaeontology collections contain a treasure trove of fossils that await rediscovery. But new discoveries straight from the field are particularly exciting – and this is where Attenborough steps in …</p>
<h2>A new ‘dragon’</h2>
<p>In 2016, I was in contact with somebody at the BBC regarding a possible new one-off documentary on ichthyosaurs, presented by Sir David Attenborough. David has a bit of a soft-spot for ichthyosaurs, you see.</p>
<p>Excited probably doesn’t quite capture what I was feeling, given that ichthyosaurs have pretty much been my life for ten or so years and I grew up watching Attenborough documentaries. Anyway, the idea was based around a new ichthyosaur discovery in Dorset. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/200949/original/file-20180105-26169-19il3ve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/200949/original/file-20180105-26169-19il3ve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/200949/original/file-20180105-26169-19il3ve.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/200949/original/file-20180105-26169-19il3ve.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/200949/original/file-20180105-26169-19il3ve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/200949/original/file-20180105-26169-19il3ve.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/200949/original/file-20180105-26169-19il3ve.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">David Attenborough examines the fossil.</span>
<span class="attribution"><span class="source">BBC/Robin Cox</span></span>
</figcaption>
</figure>
<p>I had actually already been aware of this discovery (in early 2016), as I am long-time friends with the collector, an excellent chap called Chris Moore. I met Chris when I was about 17 years old. He is one of the best fossil collectors I have ever met. He just has a gift when it comes to finding new or rare fossils. For example, one ichthyosaur specimen he found back in January, 1995, turned out to be a new species. It was named <em><a href="http://onlinelibrary.wiley.com/doi/10.1111/1475-4983.00096/pdf">Leptonectes moorei</a></em>, in honour of Chris. He has certainly got an eye for recognising something rare.</p>
<p>The documentary thus focuses on telling the life story of Chris’ 2016 ichthyosaur specimen. From how it lived, what it would have looked like, to ultimately how it died. Several of my colleagues, including Emily Rayfield, Ben Moon, and Fiann Smithwick (all from the University of Bristol) were on hand to help piece together this 200m-year-old puzzle. </p>
<p>Various other colleagues, including Cindy Howells (National Museum of Cardiff) and Steve Etches (The Etches Collection – Museum of Jurassic Marine Life) also helped. The specimen itself is almost complete, although, sadly, is missing the skull. But therein lies the mystery, and part of the story. It is thought that the animal may have been killed from an attack by another ichthyosaur. So, perhaps this is a 200m-year-old crime scene, even what the BBC publicity has called a <a href="http://www.bbc.co.uk/programmes/b09m2kgl">“murder mystery”</a>?</p>
<p>I have yet to see the documentary, and am looking forward to seeing it. However, I have read, in various press articles, that this specimen has been hailed a new species. </p>
<p>I actually disagree with this. I have seen the specimen, well parts of it, and the forefin matches what is known for the ichthyosaur genus, <a href="http://onlinelibrary.wiley.com/doi/10.1002/spp2.1065/pdf"><em>Ichthyosaurus</em></a>. The forefin of <em>Ichthyosaurus</em> is unique to the genus, and the forefins of Chris’ new specimen, match perfectly. Indeed, they probably belong to <em><a href="https://www.cambridge.org/core/journals/geological-magazine/article/an-ichthyosaurus-breviceps-collected-by-mary-anning-new-information-on-the-species/860729195FFDE7504DB6214F5C7D7FCB">Ichthyosaurus breviceps</a></em>, a short-snouted species, known from about 30 specimens – although Chris’ specimen, if it is an <em>Ichthyosaurus breviceps</em>, would be the largest known. </p>
<p>Of course, without a skull, it is difficult to say for certain what species this specimen belongs to, or what really happened to it, and I’m interested to see whether the mystery is finally solved.</p><img src="https://counter.theconversation.com/content/89688/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dean Lomax 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>As a new David Attenborough documentary examines a remarkable fossil, a leading expert gives his verdict.Dean Lomax, Visiting Scientist (Palaeontologist), University of ManchesterLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/757322017-09-19T17:57:52Z2017-09-19T17:57:52ZForgotten fossils hold clues to how ancestors of mammals cared for their young<p>We all know that mammals protect and care for their young. In some cases, they also live within complex social groups. Was this always the case? </p>
<p>The skeletal anatomy of mammals’ early ancestors has been studied for more than 150 years. But until relatively recently, not much was known about their lifestyle or reproductive habits. It wasn’t clear whether these extinct animals protected and cared for their young in the same way as modern mammals do.</p>
<p>But a few decades ago a clue to their behaviour was discovered in two remarkable fossils found in South Africa that date back 251 million years ago. The significance of these fossils of <em>Thrinaxodon liorhinus</em> and <em>Galesaurus planiceps</em> have been largely forgotten by the palaeontological community and they were left out of recent discussions about parental care in the fossil record. We rediscovered them while doing other research and decided to <a href="https://peerj.com/articles/2875/">reinvestigate their significance</a>.</p>
<p>The fossils are even more important than we imagined. They provide direct evidence of parental care in these extinct animals. They also reveal complex behaviour in our own distant ancestors.</p>
<h2>The first discoveries</h2>
<p>The <em>Thrinaxodon</em> and <em>Galesaurus</em> fossils date back to the Early Triassic period, soon after the <a href="http://science.nationalgeographic.com/science/prehistoric-world/permian-extinction/">end-Permian mass extinction</a> and before the age of dinosaurs. </p>
<p>Mammals hadn’t yet evolved. But their ancestors, the non-mammalian <a href="https://global.britannica.com/animal/cynodont">cynodonts</a>, had a few features we recognise today in mammals: teeth differentiated into incisors, canines and complex postcanines, and the presence of a secondary palate. The fossils of <em>Thrinaxodon</em> and <em>Galesaurus</em> represented the first possible cases of parental care reported in non-mammalian cynodonts. This is significant because mammals didn’t evolve for another 30 million years.</p>
<p>The <em>Thrinaxodon</em> fossil was found in 1954 by the renowned Karoo fossil hunter James Kitching. Dr. A.S. Brink, a palaeontologist at Johannesburg’s University of the Witwatersrand, briefly <a href="http://wiredspace.wits.ac.za/handle/10539/14873">described</a> it as consisting of an adult skull preserved next to a small juvenile about a third of its size. Brink hypothesised that this represented a case of parental care.</p>
<p>In 1965 Brink discovered a second case of parental care in <em>Galesaurus planiceps</em>, a larger basal cynodont about the size of a fox. The <em>Galesaurus</em> fossil block contained the skeleton of an adult surrounded by juveniles. Brink interpreted this fossil as evidence of a mother caring for her young.</p>
<p>These remarkable fossils became part of the collection of the <a href="https://www.wits.ac.za/esi/">Evolutionary Studies Institute</a> at the University of the Witwatersrand. We came across them while investigating ontogenetic growth in <a href="http://onlinelibrary.wiley.com/doi/10.1002/ar.23116/abstract"><em>Thrinaxodon</em></a> and <a href="http://onlinelibrary.wiley.com/doi/10.1002/ar.23473/abstract"><em>Galesaurus</em></a>. We wanted to find out how these cynodonts’ skull changed as they grew from a small juvenile into a large adult. In the course of our work, we realised that these fossils were also telling a forgotten story about nurturing behaviour in our very distant ancestors.</p>
<p>Some further work had been done on the <em>Thrinaxodon</em> fossil since Brink’s 1955 description. The skulls are now separated from each other and acid-preparation led to the discovery of a second juvenile individual. But the <em>Galesaurus</em> fossil was found tucked away in a drawer in collections, with no evidence of further preparation or study.</p>
<p>We were intrigued, and decided to reinvestigate what the fossils might tell us about parental care among the ancestors of mammals. </p>
<h2>Our findings</h2>
<p>Our study concluded that in both cases there were two young juveniles associated with each adult.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/175164/original/file-20170622-12008-qrinid.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/175164/original/file-20170622-12008-qrinid.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=419&fit=crop&dpr=1 600w, https://images.theconversation.com/files/175164/original/file-20170622-12008-qrinid.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=419&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/175164/original/file-20170622-12008-qrinid.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=419&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/175164/original/file-20170622-12008-qrinid.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=526&fit=crop&dpr=1 754w, https://images.theconversation.com/files/175164/original/file-20170622-12008-qrinid.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=526&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/175164/original/file-20170622-12008-qrinid.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">
<figcaption>
<span class="caption"><em>Galesaurus</em> parental care fossil consisting of one adult surrounded by two juveniles.</span>
<span class="attribution"><span class="source">From Jasinoski and Abdala (2017). DOI: 10.7717/peerj.2875/fig-3</span></span>
</figcaption>
</figure>
<p>We then investigated more than 100 fossils of <em>Thrinaxodon</em> and <em>Galesaurus</em> from South Africa to determine how often individuals of each genus were preserved together. The bones of individuals that were found together in the same fossil block or in close proximity were, in many cases, preserved in “life position”. </p>
<p>This suggests that these animals were living together in a group – what’s known as an <a href="https://www.jstor.org/stable/2808323?seq=1#page_scan_tab_contents">aggregation</a> – before they died and were fossilised.</p>
<p>The research we’d already done into ontogenetic classification really helped. We had sorted the <em>Thrinaxodon</em> and <em>Galesaurus</em> specimens into juvenile, subadult, or adult stages. This meant we could determine whether the aggregation consisted of individuals of the same age – for example, all adults – or represented a mixed-age group, such as an adult with juveniles.</p>
<p>Overall, we found that <em>Thrinaxodon</em> had a higher occurrence of aggregations than <em>Galesaurus</em>. These groups were comprised of individuals of either similar or different ontogenetic ages.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/185723/original/file-20170912-3748-1oubdpq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/185723/original/file-20170912-3748-1oubdpq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=346&fit=crop&dpr=1 600w, https://images.theconversation.com/files/185723/original/file-20170912-3748-1oubdpq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=346&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/185723/original/file-20170912-3748-1oubdpq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=346&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/185723/original/file-20170912-3748-1oubdpq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=434&fit=crop&dpr=1 754w, https://images.theconversation.com/files/185723/original/file-20170912-3748-1oubdpq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=434&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/185723/original/file-20170912-3748-1oubdpq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=434&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A graph showing the number and type of aggregations found in <em>Galesaurus</em> and <em>Thrinaxodon</em>. Aggregations were classified as same-age or mixed-age based on previous cranial ontogenetic studies of these two cynodonts. Abbreviations: juv, juvenile; subad, subadult.</span>
<span class="attribution"><span class="source">Supplied by authors</span></span>
</figcaption>
</figure>
<p>In <em>Thrinaxodon</em>, we found four aggregations consisting of same-age individuals and three aggregations among mixed-age individuals – including the parental care case described by Brink. This is in stark contrast to <em>Galesaurus</em>: here, only one other aggregation, among three sub-adult individuals, was found in addition to the parental care case. These findings suggest that <em>Thrinaxodon</em> regularly lived within a group.</p>
<p>The two parental care fossils Brink described showed the largest discrepancy in size among aggregating individuals. This implies he was right: these fossils do indeed represent cases of parental care. </p>
<p>The juveniles in each parental care fossil represent the smallest recorded individuals for both genera, suggesting they were newborns. In addition, the juveniles of each genus are similar in size to each other. That indicates they might have been siblings. We also confirmed that the adult <em>Galesaurus</em> individual represented a “female” – so, a mother – based on our previous discovery of <a href="http://onlinelibrary.wiley.com/doi/10.1002/ar.23473/abstract">sexual dimorphism</a> in this genus.</p>
<h2>Parenting in the past</h2>
<p>Parental care was present in both of these cynodonts, but the evidence to date suggests that <em>Galesaurus</em> cared for its young for a relatively longer period of time. This is because the skull of the <em>Galesaurus</em> juveniles is about half the size of the largest known adult, and it is relatively much larger than the <em>Thrinaxodon</em> juveniles. This discrepancy in size also supports our previous idea that <em>Thrinaxodon</em> matured relatively earlier than <em>Galesaurus</em>.</p>
<p>What these fossils show is that parental care instincts were already established 251 million years ago in two different species of mammal forerunners. This indicates that complex behaviour generally attributed to living mammals has a long history, stretching back millions of years.</p><img src="https://counter.theconversation.com/content/75732/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sandra Jasinoski received postdoctoral funding from the DST-NRF Centre of Excellence in Palaeosciences.</span></em></p><p class="fine-print"><em><span>Fernando Abdala 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>Two fossils found in South Africa provide direct evidence of parental care in extinct pre-mammalian ancestors.Sandra Jasinoski, Honorary Associate, University of the WitwatersrandFernando Abdala, Reader, Evolutionary Studies Institute, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/799612017-07-18T10:23:24Z2017-07-18T10:23:24ZMore than 252 million years ago, mammal ancestors became warm-blooded to survive mass extinction<figure><img src="https://images.theconversation.com/files/177875/original/file-20170712-19675-1n78i80.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The skeleton of a therapsid dicynodont _Lystrosaurus_.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/93645864@N03/29568366190/">Flickr</a></span></figcaption></figure><p>Today mammals and birds are the only true warm-blooded animals. They are called endotherms, meaning they produce their body heat internally.</p>
<p>Endotherm animals are the opposite to ectotherms which get their heat from an external factor like the sun. They are considered “cold-blooded”.</p>
<p>The origins of warm-bloodedness in mammals has been a very controversial issue for two reasons. One is that several of the anatomical features thought to be linked to warm-bloodedness have also been found in cold-blooded reptiles. The other is that these characteristics are not always preserved in fossils, giving scientists inconsistent signals about the presence of warm-bloodedness.</p>
<p><a href="https://elifesciences.org/articles/28589">Our research</a> helps shed new light on this controversy. We’ve been able to come up with new insights about how mammals developed a warm-blooded metabolism that may have helped them survive the terrible mass extinction that marked the end of the Permian period, 252 million years ago.</p>
<p>By comparing the ratios of oxygen isotope in fossils we were able to show that a group called the cynodontia – mammal ancestors – acquired warm-bloodedness somewhere during the Late Permian period, which ranged from 259 to 252 million years ago. This makes the origin of mammal endothermy older than what we thought previously.</p>
<p>But our research also shows that the cynodontia were not the only ones to acquire warm-bloodedness. The dicynodontia, which have been considered cold-blooded, also developed this feature independently in the same time period. </p>
<p>Our discovery suggests that climate was the main factor that triggered the evolution of warm-bloodedness in mammals and it’s responsible for subsequent mammalian evolutionary success. We argue that triassic dicynodonts and cynodonts were able to survive by already possessing an endothermic metabolism to cope with temperature fluctuations.</p>
<h2>Mammalian characteristics</h2>
<p>There are several special features that are linked to warm-bloodedness. One is the bones inside the nose and snout, called the turbinates. These bones increase the distance that air travels into the body, allowing it to warm up on the way in. There is also the bony palate which separates the mouth from the nose and allows for continuous breathing, even while eating. Another, which is rarely preserved in the fossil records, is the presence of fur which acts as an insulating layer.</p>
<p>The challenge with evaluating the origins of morphological features is that they aren’t from the same time. Some have appeared in some animals earlier than others. </p>
<p>So we took an innovative and unprecedented approach. We looked at the isotopes of oxygen in the bones and teeth of Permo-Triassic mammal-like reptiles known as therapsids. This is an approach that’s been used officially to evaluate <a href="http://www.sciencedirect.com/science/article/pii/S0012821X06003050">dinosaurs</a>. </p>
<p>The transition between the Permian and Triassic periods, 252 million years ago, is known as the most devastating mass extinction in <a href="http://www.sciencedirect.com/science/article/pii/S0169534703000934">Earth’s history</a>. Reconstructions of the paleoclimate show that after a cooling trend towards the end of the Permian period, there was an abrupt and intense warming at the <a href="http://www.sciencedirect.com/science/article/pii/S1342937X15002439">Permian-Triassic Boundary</a>. </p>
<p>We took samples of groups of animals from fossil records kept in South Africa, Lesotho, Morocco and China dating to the Permian and Triassic period.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/178610/original/file-20170718-21991-142ukd6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/178610/original/file-20170718-21991-142ukd6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/178610/original/file-20170718-21991-142ukd6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/178610/original/file-20170718-21991-142ukd6.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/178610/original/file-20170718-21991-142ukd6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/178610/original/file-20170718-21991-142ukd6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/178610/original/file-20170718-21991-142ukd6.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">The skull of the therapsid dicynodont <em>Lystrosaurus murrayi</em> from South Africa dating to the Triassic period.</span>
<span class="attribution"><span class="source">supplied by author</span></span>
</figcaption>
</figure>
<p>We sampled therapsids and some tetrapods that lived at the same time and at the same place. By doing so we were able to distinguish warm-blooded therapsids from cold-blooded ones, and get closer to pinning down when species evolved to warm-bloodedness.</p>
<p>We found that Permian therapsids and the co-existing tetrapods had similar body temperatures. But, in contrast, analysed therapsids in the Triassic period were warm-blooded. </p>
<p>Both the dicynodonts and cynodonts in the Permian period were cold-blooded while the same groups in the Triassic period were warm-blooded. This means that they acquired their endothermy in the late Permian period. </p>
<p>Understanding that these groups developed their warm-bloodedness during the Late Permian period highlights two important findings. </p>
<p>The first is that they appeared independently – the Permian ancestors of both groups were not warm-blooded. The second is, even if they may have appeared at different times during the Late Permian period, they seem to have been through the same factors of selection by surviving the global climatic variations of the end-Permian.</p>
<p>The “mammal-like reptiles” survived because warm-blooded animals have the capacity to produce their own body heat which allows them to live in colder environments or in areas with huge seasonal temperature contrasts. </p>
<p>At the geological scale, this could mean that endothermic species would have a better chance to survive through important and rapid climate change.</p><img src="https://counter.theconversation.com/content/79961/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kevin Rey 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>Climate was the main factor that triggered the evolution of warm-bloodedness in mammals and the subsequent mammalian evolutionary success.Kevin Rey, Postdoctoral researcher, Evolutionary Studies Institute, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/728262017-02-14T16:01:42Z2017-02-14T16:01:42ZPregnant fossil shows bird and crocodile ancestors gave birth to live young<figure><img src="https://images.theconversation.com/files/156830/original/image-20170214-25972-19hs5uy.png?ixlib=rb-1.1.0&rect=119%2C0%2C4281%2C2133&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Dinghua Yang & Jun Liu</span></span></figcaption></figure><p>Giving birth to live young is one of the traits we use to distinguish mammals from other animals. But certain <a href="https://theconversation.com/lizards-help-us-find-out-which-came-first-the-baby-or-the-egg-29954">kinds of lizards</a>, snakes and amphibians, both living and extinct, also reproduce without laying eggs. In fact, live birth (or viviparity) has evolved more than 100 separate times in non-mammal species throughout history. It seems to have been a common reproductive strategy in particular for <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0088640">extinct aquatic reptiles</a>, such as the fish-like ichthyosaurs, plesiosaurs and mosasaurs that lived at the same time as the dinosaurs.</p>
<p>But one group of animals known as Archosauromorpha, which include crocodiles, birds and their ancestors the dinosaurs, has never been known to give birth – until now. A recently unearthed fossil, described <a href="http://nature.com/articles/doi:10.1038/ncomms14445">in a new study</a> by a team of scientists from China, the US, UK and Australia, shows that an ancient species of archosauromorph was giving birth around 245m years ago.</p>
<p>The newly described specimen belongs to the species <em>Dinocephalosaurus orientalis</em> and was found in sediments from the early Triassic period in Yunnan Province, China. <em>Dinocephalosaurus</em> had a body length of around a metre but with an elongated neck of nearly twice that length. Its skull was relatively small and equipped with needle-like teeth adapted to catch fish and squids.</p>
<p>The shape of its skeleton suggests that it lived in water, but scientists originally thought it might have ventured onto land to lay eggs, as all known archosauromorphs do. The new fossil find now proves this theory to be wrong because it was found with an embryo preserved in its abdominal region. This provides compelling evidence for that this species of archosauromorphs gave birth to live young.</p>
<h2>Compelling evidence</h2>
<p>It is often hard to reconstruct a picture of an extinct creature and how it lived from a fossil, but a number of features strongly suggest that the new specimen does indeed represent a pregnant <em>Dinocephalosaurus</em>. The embryo’s skeleton has a very similar shape to the adult’s, showing that both belonged to the same species and that the embryo was in a very mature stage. The embryo is fully enclosed by the bones of the adult specimen and located in the pelvic region.</p>
<p>Remains of a partially digested fish were also found further up and between the ribs of the adult. This not only helps us identify the mother’s last meal, but also rules out the possibility that the embryo might have been devoured prey.</p>
<p>The embryo was also found in a curled-up position with the neck pointed towards the chest and forelimbs, which is a typical pose for vertebrate embryos. The withering of soft tissues such as muscles after an adult vertebrate dies means they are often fossilised in a <a href="http://phenomena.nationalgeographic.com/2015/12/30/flexible-necks-made-the-classic-dinosaur-death-pose/">typical death pose</a> with the neck and tail arched back.</p>
<p>In this case, the mother animal was preserved in exactly this position but not the embryo. This makes it unlikely that both fossils died at different times and came to lie on top of each other by coincidence. Together, this provides good evidence that the new fossil is indeed that of a pregnant <em>Dinocephalosaurus</em> and its embryo.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/156802/original/image-20170214-25977-1lrrb3p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/156802/original/image-20170214-25977-1lrrb3p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=316&fit=crop&dpr=1 600w, https://images.theconversation.com/files/156802/original/image-20170214-25977-1lrrb3p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=316&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/156802/original/image-20170214-25977-1lrrb3p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=316&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/156802/original/image-20170214-25977-1lrrb3p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=397&fit=crop&dpr=1 754w, https://images.theconversation.com/files/156802/original/image-20170214-25977-1lrrb3p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=397&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/156802/original/image-20170214-25977-1lrrb3p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=397&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Fossilised dinosaur eggs were our only evidence until now.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/23165290@N00/9325347404/">Tim Evanson/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Exceptionally preserved fossils, such as this one, allow a unique glimpse into the life of organisms over 245m years ago, but they also have more far-reaching implications. Until now, it was assumed that all Archosauromorpha laid eggs. Modern members, represented by birds and crocodiles, are without exception oviparous (egg-laying), and fossilised eggs of dinosaurs <a href="http://science.sciencemag.org/content/331/6015/321">and pterosaurs</a> further supported this assumption.</p>
<p>Finding a pregnant <em>Dinocephalosaurus</em> demonstrates that at least some extinct archosauromorphs were giving birth to living young. It also means our knowledge of how archosauromorphs reproduced goes back 50m years further than was previously possible. Until now, our <a href="http://www.pnas.org/content/109/7/2428.full">oldest relevant fossils</a> of this group were dinosaur eggs from the early Jurassic period (around 190m years ago).</p>
<p>The results of this study also raise several questions. <a href="https://www.ncbi.nlm.nih.gov/pubmed/25904118">Viviparity has evolved</a> independently and numerous times in all major types of vertebrate, with mammals probably the most prominent and successful example. Although giving birth is physically and energetically taxing for the parent, it has <a href="https://www.researchgate.net/publication/233720348_Viviparity_and_oviparity_Evolution_and_reproductive_strategies">clear advantages</a> for the offspring, which receives extra nutrients and protection, and develops without being affected by environmental conditions. </p>
<p>Yet archosauromorphs evolved away from this reproductive strategy to become the egg-laying dinosaurs, and eventually crocodiles and birds that we know. Why was this? We will now have to hope that future fossil finds might reveal another piece to the evolutionary puzzle.</p><img src="https://counter.theconversation.com/content/72826/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephan Lautenschlager has received funding from the Natural Environment Research Council (NERC). </span></em></p>A 245m year old fossil is the first evidence that of live births in one of the major groups of animals.Stephan Lautenschlager, Lecturer in Palaeobiology, University of BirminghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/603382016-06-07T14:04:21Z2016-06-07T14:04:21ZHow looking 250 million years into the past could save modern species<figure><img src="https://images.theconversation.com/files/125538/original/image-20160607-15031-aifndq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A Permo-Triassic boundary site near Bethulie in South Africa's Free State province. </span> <span class="attribution"><span class="source">Supplied</span></span></figcaption></figure><p><em>More than 250 million years ago, something huge happened to the Earth: the <a href="http://science.nasa.gov/science-news/science-at-nasa/2002/28jan_extinction/">Permo-Triassic Mass Extinction</a> (PTME), which wiped out almost all of the planet’s species. Now a group of scientists has <a href="http://www.nature.com/articles/srep24053">uncovered</a> important details about how the event’s survivors adapted in a harsh, drought-stricken stretch of South Africa. The Conversation Africa’s science and technology editor Natasha Joseph asked lead researcher Dr Jennifer Botha-Brink to explain what she and her colleagues have learnt – and what this might teach us about species’ adaptation to climate change.</em></p>
<p><strong>Lots of research has been done about this period and its impact. What was your research trying to understand, specifically?</strong></p>
<p>There have been five major mass extinctions in Earth’s history and the PTME was by far the most catastrophic, killing 70% of all terrestrial species and somewhere between 80% and 96% of all marine species. The environment changed from a world with abundant vegetation, large meandering rivers and a temperate climate to a highly seasonal, drought-stricken, unpredictable environment. The world’s ecosystems did not fully recover until some five million years after the extinction event. </p>
<p>The aim of our research was to discover the changes, if any, that occurred in vertebrate life histories across the PTME. In other words, how did the survivors adapt to the harsh, unpredictable, drought-stricken post-extinction environment? To try and answer this question, we compared the growth patterns of Permian (pre-extinction) and Triassic (post-extinction) therapsids – they were the ancient ancestors of mammals – by looking at their bone microstructure. </p>
<p>The bone microstructure, or histology, of extinct vertebrates gives a unique view on how they lived. It provides information about how quickly an animal grew, the manner in which it grew, when it matured – that’s the age it was at skeletal and possibly reproductive maturity – and how old it was when it died. This information allows us to reconstruct the animal’s life history.</p>
<p>Comparing the life histories of therapsids that lived before and after the extinction allowed us to identify differences in the Early Triassic animals that may have helped them survive the PTME. Our results help explain how some species that thrive in post-extinction environments, such as the therapsid <a href="http://study.com/academy/lesson/lystrosaurus-facts-lesson-quiz.html">Lystrosaurus</a>, not only survived but spread to all areas of the globe and became the most abundant vertebrate after the PTME.</p>
<p><strong>Your research was focused on therapsids that had occurred in South Africa’s Karoo Basin. How large an area is that, and why did you choose it as the site for your work?</strong></p>
<p>The South African Karoo Basin contains the best, most complete terrestrial record of the PTME. It covers some 730,000km² of the interior of South Africa. Thousands of therapsid fossils have been found in these strata, providing a complete fossil record through the Permo-Triassic boundary. There was enough material from many different therapsid species to allow us to obtain the information required for this type of analysis. It is the best place for studying the PTME and its influence on animal and plant life histories.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/125400/original/image-20160606-13043-79271p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/125400/original/image-20160606-13043-79271p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/125400/original/image-20160606-13043-79271p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/125400/original/image-20160606-13043-79271p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/125400/original/image-20160606-13043-79271p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/125400/original/image-20160606-13043-79271p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=440&fit=crop&dpr=1 754w, https://images.theconversation.com/files/125400/original/image-20160606-13043-79271p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=440&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/125400/original/image-20160606-13043-79271p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=440&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An illustration of the Lystrosaurus.</span>
<span class="attribution"><span class="source">Maggie Lambert-Newman</span></span>
</figcaption>
</figure>
<p><strong>How did you extract the data you needed? And what was it you were looking for in those fossils – what stories did they tell you?</strong></p>
<p>Our analysis focused on fossil bone microstructure and body size measurements. Limb bones were sectioned using specialised cutting and grinding equipment. Thin slivers of the fossil bone were then fixed to glass slides and examined under a microscope. Although the organic components of the bone have long since disappeared, the orientation of the bone tissue fibres, the spaces for marrow, blood vessels and bone cells remain intact. This allows us to compare growth patterns and rates between different species. </p>
<p>We also obtained body size data by measuring the skull lengths of as many therapsid specimens as possible. These measurements were used to compile body size distributions so we could compare the demographics between Permian and Triassic therapsid species. All the data were then combined to assess the ecology of Permian and Triassic therapsids. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/125401/original/image-20160606-13040-1wiwypt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/125401/original/image-20160606-13040-1wiwypt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/125401/original/image-20160606-13040-1wiwypt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1029&fit=crop&dpr=1 600w, https://images.theconversation.com/files/125401/original/image-20160606-13040-1wiwypt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1029&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/125401/original/image-20160606-13040-1wiwypt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1029&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/125401/original/image-20160606-13040-1wiwypt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1293&fit=crop&dpr=1 754w, https://images.theconversation.com/files/125401/original/image-20160606-13040-1wiwypt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1293&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/125401/original/image-20160606-13040-1wiwypt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1293&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 Lystosaurus skeleton, which was examined to understand how the species adapted to a massive extinction event.</span>
<span class="attribution"><span class="source">Jennifer Botha-Brink</span></span>
</figcaption>
</figure>
<p>We also used the data to create a theoretical model showing what kind of features would have helped the post-extinction therapsids to survive. The bone microstructure and body size data showed that Early Triassic therapsids grew quickly to skeletal and reproductive maturity and then died at young ages. The simulations of population growth supported our results by showing that reproducing at young ages would indeed have helped the survivors to persist in the harsh, unpredictable post-extinction environment.</p>
<p><strong>Your work focused on extinct species. What are its applications today? What can it tell us about how species might cope with another big “die-out”?</strong></p>
<p>Research on past extinctions provides data on how ecosystems change in response to severe climate change. It also shows how species adapt to their new environment. This information can be applied to today’s world, which is currently in the midst of a <a href="http://www.theguardian.com/environment/radical-conservation/2015/oct/20/the-four-horsemen-of-the-sixth-mass-extinction">sixth mass extinction</a>. </p>
<p>We can use information from the past to predict which species might survive and which may be more sensitive to extinction. In this way we can learn how to conserve susceptible species such as those that take many years to reach adulthood. Those that take longer to breed or have few young may be more likely to become extinct than those that breed when they are still young and have many babies.</p><img src="https://counter.theconversation.com/content/60338/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jennifer Botha-Brink receives funding from the National Research Foundation, the DST/NRF Centre of Excellence for Palaeosciences and the Palaeontological Scientific Trust and its Scatterlings of Africa programmes. </span></em></p>How did survivors of the Permo-Triassic Mass Extinction adapt to their new, harsh environment? And why is that knowledge so important for modern species?Jennifer Botha, Specialist Museum Scientist and Head of Department (National Museum, Bloemfontein) and Research Affiliate, University of the Free StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/445712015-07-16T02:59:20Z2015-07-16T02:59:20ZPlate tectonics may have driven the evolution of life on Earth<figure><img src="https://images.theconversation.com/files/88279/original/image-20150714-11798-1l5y1ud.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The cycles of nutrients into the oceans following the building of mountains may have been a prime driver of evolutionary change.</span> <span class="attribution"><span class="source">John Long, Flinders University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>When <a href="http://www.biography.com/people/charles-darwin-9266433">Charles Darwin</a> published his theory of evolution by natural selection in 1859, the world hadn’t even heard of <a href="http://csmres.jmu.edu/geollab/vageol/vahist/plates.html">plate tectonics</a>. The notion that continents drifted on molten rock currents deep in the Earth’s mantle was unimaginable.</p>
<p>So it would have come as a shock to Darwin to think the movement of the Earth’s continental plates could have been a major driver of evolutionary change in all life.</p>
<p>In our research, published this month in <a href="http://www.sciencedirect.com/science/article/pii/S1342937X15001537">Gondwana Research</a>, we suggest that the regular collision of tectonic plates over the past 700 million years has been a prime driver of evolutionary change on Earth.</p>
<h2>The essentials for life</h2>
<p>We used <a href="https://secure.utas.edu.au/earth-sciences/facilities/laicpms-laboratory">laser technology</a> housed in the Earth Science laboratories at the University of Tasmania to analyse more than 4,000 pyrite grains from seafloor mudstone samples collected from around the globe.</p>
<p>This enabled us to determine how concentrations of trace elements in the oceans have varied over the 700 million years. <a href="http://www.sciencemag.org/content/213/4514/1332.short">Trace elements</a> included copper, zinc, phosphorus, cobalt and selenium, which are necessary for nearly all life – from marine <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.0022-3646.1987.00001.x/abstract">phytoplankton</a> through to <a href="https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/#h5">humans</a> – to function. </p>
<p>The most surprising finding was that there were certain periods in Earth’s history when nutrient trace elements were highly enriched in the oceans, and other periods when levels of these critical trace elements were very low.</p>
<p>The nutrient-rich periods promoted rapid plankton growth in the short term, and this appears to correlate with periods of increased evolutionary change. An example of this is the rapid rise in trace elements preceding the <a href="http://www.ucmp.berkeley.edu/vendian/ediacaran.php">Ediacaran</a> (635 to 542 million years ago) and <a href="http://www.ucmp.berkeley.edu/cambrian/cambrian.php">Cambrian</a> (541 to 485 mya) periods, a time when multicellular animal life took off in a big way.</p>
<p>The <a href="http://www.bbc.co.uk/science/earth/earth_timeline/cambrian_explosion">Cambrian explosion</a>, around 540 million years ago, is when most major groups of living animals appeared. This corresponds to a time when essential trace elements were peaking in the oceans, thus nutrient levels were very high.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/88187/original/image-20150713-14709-csh315.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/88187/original/image-20150713-14709-csh315.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/88187/original/image-20150713-14709-csh315.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=408&fit=crop&dpr=1 600w, https://images.theconversation.com/files/88187/original/image-20150713-14709-csh315.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=408&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/88187/original/image-20150713-14709-csh315.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=408&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/88187/original/image-20150713-14709-csh315.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=513&fit=crop&dpr=1 754w, https://images.theconversation.com/files/88187/original/image-20150713-14709-csh315.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=513&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/88187/original/image-20150713-14709-csh315.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=513&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 Cambrian explosion about 540 million years ago was when all the major living groups (phyla) of animal life appeared. Did a rise in oceanic trace elements initiate this event?</span>
<span class="attribution"><a class="source" href="http://dinopedia.wikia.com/wiki/Cambrian">Wikia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The nutrient-poor periods caused depletion of plankton and promoted a slow-down in rates of diversification and ultimately could have played a role in three major <a href="http://www.bbc.co.uk/nature/extinction_events">mass extinction events</a>. These occurred at the end of the <a href="http://www.ucmp.berkeley.edu/ordovician/ordovician.php">Ordovician</a>, <a href="http://www.ucmp.berkeley.edu/devonian/devonian.php">Devonian</a> and <a href="http://www.ucmp.berkeley.edu/mesozoic/triassic/triassic.html">Triassic</a> periods.</p>
<p>Although <a href="http://www.endangeredspeciesinternational.org/overview.html">several possible explanations</a> are given for these extinctions events, depletion in oceanic trace elements might be another plausible factor. Work is currently underway demonstrating that these events are tied to rapid declines in certain essential trace elements, particularly selenium.</p>
<h2>Plate tectonics and nutrient cycles</h2>
<p>Nutrients in the oceans ultimately come from weathering and erosion of rocks on the
continents. Weathering breaks down the minerals in the rocks and releases the
nutrient trace elements, which nourish life. Thus when weathering and erosion rates increase for extended periods, more nutrients are supplied to the oceans.</p>
<p>In the long term of geological history, erosion rates rise dramatically during
mountain building events caused by the gradual collision of tectonic plates.</p>
<p>Geologists have known since the 1960s that collisions of tectonic plates lead to the formation of huge mountain ranges. The <a href="http://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Convergent/Continental-Collision">Himalayas were formed</a> when India, drifting northwards after splitting off from the supercontinent of Gondwana, slammed into Asia and pushed up the Tibetan Plateau. These collisions are called called <a href="http://www.britannica.com/science/orogeny">orogenic events</a> and their timing through Earth’s history is now well established.</p>
<p>Continued erosion eventually depletes the surface of nutrients, causing a drop in the ocean’s nutrients. This might have lead to extinction events in the seas.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/88183/original/image-20150713-1501-150g4jh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/88183/original/image-20150713-1501-150g4jh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/88183/original/image-20150713-1501-150g4jh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=344&fit=crop&dpr=1 600w, https://images.theconversation.com/files/88183/original/image-20150713-1501-150g4jh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=344&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/88183/original/image-20150713-1501-150g4jh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=344&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/88183/original/image-20150713-1501-150g4jh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=432&fit=crop&dpr=1 754w, https://images.theconversation.com/files/88183/original/image-20150713-1501-150g4jh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=432&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/88183/original/image-20150713-1501-150g4jh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=432&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">When tectonic plates collide, mountains are pushed upwards and erosion causes an increase in nutrients in the oceans.</span>
<span class="attribution"><span class="source">Ross Large, University of Tasmania</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>This is the first time nutrient trace element curves have been developed that demonstrate the relationship between tectonic collisions and the generation of cycles of nutrients.</p>
<p>While the link between these nutrient cycles as drivers of evolution and factors in mass extinction events remains to be proven, it really makes us think about evolution in a broad sense. Plate tectonics and evolution both operate on the same time scale of millions of years, and it seems logical that they could be causally related. </p>
<p>The relationship between increased nutrients in the oceans with bursts of evolutionary change are clearly correlated for the early part of the cycles, but less clear is the correlation with the evolution of advanced land animals.</p>
<h2>Life out of the oceans</h2>
<p>The origin of the first land animals, <a href="http://www.ucmp.berkeley.edu/vertebrates/tetrapods/tetraintro.html">tetrapods</a> about 370 million years ago, corresponds with a decrease in oceanic nutrients and a series of <a href="http://www.devoniantimes.org/opportunity/massExtinction.html">mass extinction events</a> in the oceans. This could explain why certain <a href="http://evolution.berkeley.edu/evolibrary/article/evograms_04">sarcopterygian fishes with robust limbs </a> left the seas when they did in order to leave the nutrient-poor ocean and make out on land.</p>
<p>But the first appearance of <a href="http://paleobiology.si.edu/geotime/main/htmlversion/triassic3.html">dinosaurs and mammals</a> in the early Triassic, about 225 million years ago, has no correlation with trace element abundance.</p>
<p>Perhaps the cycles pertain mainly to biodiversity in the oceans. There is certainly a close correlation with the drop in nutrients and some global oceanic mass extinctions. These events are being tested and explored further in further research on selenium, to be released soon.</p><img src="https://counter.theconversation.com/content/44571/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ross Large receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>John Long receives funding from The Australian Research Council</span></em></p>The rise and fall of the essential elements for life could have influenced the way life evolved over many millions of years.Ross Large, Distinguished Professor of Geology, University of TasmaniaJohn Long, Strategic Professor in Palaeontology, Flinders UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/437192015-06-24T05:16:25Z2015-06-24T05:16:25ZHow life on Earth recovers after a devastating mass extinction<figure><img src="https://images.theconversation.com/files/86118/original/image-20150623-19374-1xdk2xj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Bye bye humanity.... now what?</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Collision_d%27une_com%C3%A8te.jpg">NASA</a></span></figcaption></figure><p>Life on Earth is entering the greatest mass extinction <a href="https://theconversation.com/earths-sixth-mass-extinction-has-begun-new-study-confirms-43432">since the death of the dinosaurs</a>, according to a major new study – and humans may be among the <a href="https://theconversation.com/the-five-biggest-threats-to-human-existence-27053">casualties</a>. Such a catastrophic loss of species would leave a huge hole in the world’s ecosystems, and all sorts of weird and wonderful life would evolve into the vacancies left behind.</p>
<p>To consider what life after a mass extinction might involve, we can look to the past. There have been five major mass extinctions in Earth’s history – though colleagues and I recently proposed <a href="http://www.bbc.co.uk/news/science-environment-32397220">a sixth</a> – and comparing current rates of change to the geological record of the “Big Five” extinctions suggests that this time the warning signs are real. </p>
<p>So let’s be pessimistic, and assume the apocalypse is going to happen. What does Earth look like afterwards?</p>
<h2>The greatest crisis in history</h2>
<p>The Permian-Triassic boundary (251m years ago) saw the greatest crisis in Earth’s history, when <a href="http://www.thamesandhudson.com/When_Life_Nearly_Died/9780500285732">at least 90% of species</a> died off. Even insects suffered huge losses – the only mass extinction in their long history.</p>
<p>The event is widely attributed to the effects of the <a href="http://www.le.ac.uk/gl/ads/SiberianTraps/Introduction.html">Siberian Traps</a> – huge volcanic outpourings of lava and associated greenhouse gases, in what is now northern Russia. This lead to global warming, ocean acidification and acid rain, marine oxygen depletion and poisoning by toxic metals such as mercury. Imagine today’s gloomiest climate predictions, but cranked up a few notches.</p>
<p>The few species that survived gave rise to all life thereafter and there has not been such a profound restructuring of ecosystems since, perhaps because this “survival of the fittest” rendered their descendants more tolerant to global change. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/86164/original/image-20150623-19397-l0u4t6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86164/original/image-20150623-19397-l0u4t6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=372&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86164/original/image-20150623-19397-l0u4t6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=372&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86164/original/image-20150623-19397-l0u4t6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=372&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86164/original/image-20150623-19397-l0u4t6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=467&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86164/original/image-20150623-19397-l0u4t6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=467&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86164/original/image-20150623-19397-l0u4t6.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">Trilobites prospered for 270m years, but they didn’t make it into the Triassic.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Trilobite_Heinrich_Harder.jpg">Heinrich Harder</a></span>
</figcaption>
</figure>
<p>What did the planet look like in the Early Triassic? It was hot – hot as hell – and seemingly lifeless over vast areas. Sea-surface temperatures reached up to 45°C in the tropics. In the vast Pangaean desert it was probably <a href="http://www.sciencemag.org/content/338/6105/366.short">even hotter</a>.</p>
<p>The heat caused land animals, marine reptiles and fish to disappear from the fossil record in all but the high latitudes, which were presumably a little cooler, for millions of years. In fact, there are several “gaps” in the Early Triassic. </p>
<p>The bulk of the world’s coal today derives from vast swathes of the Permian seed fern <em>Glossopteris</em> – a prominent casualty, whose loss led to a “<a href="http://gsabulletin.gsapubs.org/content/108/2/195.abstract">coal gap</a>” of at least 12m years. </p>
<p>A series of Early Triassic “<a href="http://www.ncbi.nlm.nih.gov/pubmed/11607638">fungal spikes</a>”, where rocks contain greatly enhanced numbers of spores, has been attributed to huge amounts of dead plant and animal matter available for fungi to feed upon. The heat, and acid rain-induced destruction of soils (which would have <a href="http://geology.gsapubs.org/content/43/2/159.full">smelled of vanilla</a>), must have rendered the planet largely uninhabitable. </p>
<p>Without plants there are no plant-eaters. Without herbivores there were no carnivores. One of the few “big” survivors on land was the “shovel lizard” <em>Lystrosaurus</em>, an odd-looking vegetarian which, in the absence of predators and competitors, <a href="http://phenomena.nationalgeographic.com/2013/05/28/lystrosaurus-the-most-humble-badass-of-the-triassic/">diversified with some success</a> during the Triassic. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/86132/original/image-20150623-19415-h2jbtt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/86132/original/image-20150623-19415-h2jbtt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=308&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86132/original/image-20150623-19415-h2jbtt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=308&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86132/original/image-20150623-19415-h2jbtt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=308&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86132/original/image-20150623-19415-h2jbtt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=386&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86132/original/image-20150623-19415-h2jbtt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=386&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86132/original/image-20150623-19415-h2jbtt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=386&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The shovel lizard dominated southern Pangaea before dinosaurs showed up.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Lystrosaurus_BW.jpg">Nobu Tamura</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The carnage was worse in the oceans, where up to 96% of species went extinct. The loss of all reef-building corals led to a 10m year Early Triassic “<a href="http://www.osti.gov/scitech/biblio/5174872">reef gap</a>”. Think of it: a world without reefs – and without all the diverse and abundant life they support. </p>
<p>But Earth wasn’t quite lifeless – and as well as <em>Lystrosaurus</em> there were marine success stories amid the horror. <em>Claraia</em> was an opportunistic genus of scallop-like bivalve that survived the end-Permian, and then <a href="http://link.springer.com/chapter/10.1007/978-3-319-04364-7_197#page-1">quickly diversified</a> to fill the vacant niches left by the almost total annihilation of the dominant Permian sea-floor dwellers, the brachiopods. <em>Claraia</em> was tough and could withstand very low oxygen levels – a trait that came in very handy when most sea-bed life was being starved of oxygen. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/86136/original/image-20150623-19386-84wrni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/86136/original/image-20150623-19386-84wrni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=783&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86136/original/image-20150623-19386-84wrni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=783&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86136/original/image-20150623-19386-84wrni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=783&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86136/original/image-20150623-19386-84wrni.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=984&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86136/original/image-20150623-19386-84wrni.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=984&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86136/original/image-20150623-19386-84wrni.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=984&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Claraia – seabed survivors.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Claraia_Clarai_Museum_Gr%C3%B6den.jpg">Museum Gröden / Wolfgang Moroder</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Dinosaur doom</h2>
<p>Perhaps the most famous and eye-catching extinction saw the death of the (non-avian) dinosaurs around 66m years ago at the Cretaceous-Tertiary boundary. As well as picture-postcard victims such as <em>T. rex</em>, the turnover in tiny plankton at the other end of the food chain saw an end to the formation of the famous Cretaceous chalk cliffs that are so widespread across Europe (the period’s name comes from the German “kreide”, meaning chalk). </p>
<p>Whether it was a meteorite, more massive volcanic eruptions, or a bit of both that did the damage, in comparison to the Permian-Triassic scenario, the death of the dinosaurs was more modest (around <a href="http://rstb.royalsocietypublishing.org/content/344/1307/11">75% of global species lost</a>) and the recovery was more rapid. Either Earth sorted itself out more quickly, or, following the “Great Dying” 185m years previously, life had become better at adapting to, and evolving with, stress. </p>
<p>Of course, dinosaurs are not exactly extinct. Birds are highly evolved dinosaurs that derive from the few dinosaurian survivors of the Cretaceous-Tertiary (K-T) event and nobody can deny their evolutionary success in the 66m years since the demise of the <a href="https://theconversation.com/take-a-t-rex-and-a-chicken-and-youll-see-how-dinosaurs-shrank-survived-and-evolved-into-birds-29996">chicken-like <em>T. rex</em></a>.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/86153/original/image-20150623-19415-kshpc1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/86153/original/image-20150623-19415-kshpc1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/86153/original/image-20150623-19415-kshpc1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=819&fit=crop&dpr=1 600w, https://images.theconversation.com/files/86153/original/image-20150623-19415-kshpc1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=819&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/86153/original/image-20150623-19415-kshpc1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=819&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/86153/original/image-20150623-19415-kshpc1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1030&fit=crop&dpr=1 754w, https://images.theconversation.com/files/86153/original/image-20150623-19415-kshpc1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1030&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/86153/original/image-20150623-19415-kshpc1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1030&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Life soon flourished after the dinosaurs were gone.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Eocene.jpg">Jay Matternes</a></span>
</figcaption>
</figure>
<p>Crocodiles and alligators – the closest living relatives of birds – are among the other prominent survivors. While it’s clear that birds’ ability to fly to oases of calm and plenty allowed them to flourish amid the upheaval of the K-T boundary, it is not obvious why crocodilians survived. Theories suggest their cold-blooded bodies (vs. the supposed <a href="https://theconversation.com/hot-fuss-is-warm-blooded-dinosaur-theory-right-or-wrong-8174">warm-blooded theropod dinosaurs</a>), their <a href="http://www.bioone.org/doi/abs/10.1671/0272-4634(2008)28%5B409%3ATOACPP%5D2.0.CO%3B2">fresh or brackish water habitat</a> or even their <a href="http://www.pbs.org/wgbh/nova/nature/extraordinary-lives-of-crocs.html">high IQ</a> enabled them to flourish.</p>
<p>The good news amid all this death and destruction is that life on Earth always recovers, even when it has been really badly damaged. Without extinction, there is no evolution – the two are intrinsically linked. </p>
<p>The earliest dinosaurs evolved 20m years after the Permian-Triassic losses. Their evolution was almost certainly driven by a freshening of climate during the “<a href="http://www.sciencedirect.com/science/article/pii/S0012825213001840">Carnian Pluvial Event</a>” (when it rained, a lot), new-found lush vegetation and the swathes of ecospace available to colonise. </p>
<p>Dinosaurs lived for 165m years before their demise, but without their death, humans probably wouldn’t be here today to do their damage. Mammals, of course, were the great beneficiaries of the dinosaurs’ downfall. </p>
<p>If humans are indeed doomed then we won’t be around to see what evolves to replace us. But rest assured, we geologists don’t take ourselves too seriously – we know that Earth is bigger than us, and it will bounce back.</p><img src="https://counter.theconversation.com/content/43719/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Bond receives funding from the Natural Environment Research Council (NERC).</span></em></p>With most species out of the way, remaining plants and animals rush to evolve into the ecological gaps.David Bond, NERC Advanced Research Fellow and Lecturer in Geology, University of HullLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/396552015-04-09T05:32:28Z2015-04-09T05:32:28ZTriassic mass extinction may give clues on how oceans will be affected by climate change<figure><img src="https://images.theconversation.com/files/77340/original/image-20150408-18036-y3pohj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mass extinction, good news for this guy. </span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/esparta/2250832672/in/photolist-4qU78S-66BE18-GqrBY-8LZWFh-nh9FNU-8MjSah-9MNcZg-7w3peb-b1tdeB-5C5Jts-7pFHLa-b2Vg9D-GXN8d-8pkqJ-7w3qfA-d83nYS-49VkLa-Y71Ch-9jciTZ-4Jutdo-5eTgDz-5G7Auz-o3aSey-rbj4ri-nK3EzJ-fRyXh-nJFq8R-6gmkHi-iqRikN-e77A7m-pG3mnn-bgzznr-bo43bw-b1FLUp-6tK9ke-aoWG96-9fumzk-dkkPkH-bmeUgH-38c686-wUMQx-bmeRYn-bmeNin-bmeQ98-bmeKKF-8EdvNp-bb4Cs2-p2C4jh-7KDJbp-roeyiw">Esparta Palma/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Just over 200m years ago, the end-Triassic mass extinction killed off more than half of the species of organisms living on Earth’s land and in the oceans. We are only just beginning to understand how this – and the period of runaway global warming that followed – changed the chemistry of open oceans.</p>
<p>The end-Triassic mass extinction marked the transition between the Triassic to the Jurassic Period and the rise of the large herbivorous dinosaurs, such as the <em>Diplodocus</em>. The extinction meant that previously abundant species were cleared from ecological niches which allowed dinosaurs to move in with little competition from other animals. The Jurassic lasted another 55m years until the beginning of the Cretaceous Period.</p>
<p>But the extinction also had profound effects on ocean ecosystems. <a href="http://www.pnas.org/content/107/15/6721.short">Previous research</a> linked the extinction to rapid global warming and changes in ocean chemistry which were caused by massive volcanic eruptions that released large amounts of greenhouse gasses into the atmosphere.</p>
<p>One of the unanswered questions has been how global warming changed the chemistry of the oceans. Some studies provide a picture of environmental changes on land and in coastal shallow seas, but until now there has been little information on the conditions of ecosystems in open ocean areas – known as pelagic zones – where water is neither close to the seabed or the shore.</p>
<p>We decided to investigate this unresolved problem, as open ocean settings better reflect global conditions in comparison to shallow coastal areas, as open oceans tend not to be subject to small climatic changes experienced by other areas such as shallow coastal regions near to shore. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/77370/original/image-20150408-18075-1sdcp43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/77370/original/image-20150408-18075-1sdcp43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=790&fit=crop&dpr=1 600w, https://images.theconversation.com/files/77370/original/image-20150408-18075-1sdcp43.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=790&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/77370/original/image-20150408-18075-1sdcp43.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=790&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/77370/original/image-20150408-18075-1sdcp43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=993&fit=crop&dpr=1 754w, https://images.theconversation.com/files/77370/original/image-20150408-18075-1sdcp43.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=993&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/77370/original/image-20150408-18075-1sdcp43.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=993&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">To hot to handle .</span>
<span class="attribution"><span class="source">Jessica Whiteside</span></span>
</figcaption>
</figure>
<h2>Toxic oceans</h2>
<p>We extracted and analysed fossilised organic molecules – known as biomarkers – that are the remains of microscopic marine organisms from sediments deposited at the bottom of what was the north-eastern Panthalassic Ocean - the vast body of water that surrounds the ancient super-continent Pangaea. The sediment is now preserved as rock exposed on the coast of Haida Gwaii (also known as the Queen Charlotte Islands) off the coast of British Columbia in Canada.</p>
<p>Different types of biomarkers signify the presence of certain groups of organisms and allow us to track their abundance in Triassic oceans. Our results show that for a 600,000-year interval immediately after the end-Triassic mass extinction, water close to the ocean surface became devoid of oxygen and was poisoned by hydrogen sulphide, a by-product of anaerobic bacteria that is extremely toxic to most other forms of life. This oxygen depletion and hydrogen sulphide poisoning disrupted the availability of nutrients, altering the food chains and causing a major disruption of marine ecosystems.</p>
<h2>Clues for the future</h2>
<p>These results are similar to another major event in the geologic record that was also caused by greenhouse gas release: the <a href="http://www.nhm.ac.uk/nature-online/life/dinosaurs-other-extinct-creatures/mass-extinctions/end-permian-mass-extinction/">end-Permian extinction</a>, the largest-known mass extinction.</p>
<p>Our team’s discoveries about the end-Triassic mass extinction event have direct relevance to today’s world because we are currently experiencing a rapid rise in the atmospheric levels of the greenhouse gas, carbon dioxide (CO<sub>2</sub>). Although the Earth was very different during the Triassic Period due to the lack of polar ice caps and higher initial CO<sub>2</sub> concentrations, the speed of CO<sub>2</sub> release from volcanic eruptions following the mass extinction is similar to those that we are experiencing today through the burning of fossil fuels. </p>
<p>The concern is that the consequences of rapidly rising atmospheric CO<sub>2</sub> levels can be expected to be similar: ocean acidification, oxygen depletion of the oceans, hydrogen sulphide poisoning and disruption of food chains through the killing off of photosynthesisers in the ocean. </p>
<p>Studies of ancient mass extinctions such as the one at the end-Triassic inform us of the possible consequences of our own CO<sub>2</sub> crisis.</p><img src="https://counter.theconversation.com/content/39655/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jessica H. Whiteside has received funding from National Science Foundation and Natural Environmental Research Council.</span></em></p>The end-Triassic mass extinction may be better known for preceding the rise of the dinosaurs, but it had a profound effect on oceans too.Jessica H. Whiteside, Lecturer in Ocean and Earth Science, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.