tag:theconversation.com,2011:/global/topics/tyrannosaurus-rex-17686/articlesTyrannosaurus rex – The Conversation2024-03-11T13:10:38Ztag:theconversation.com,2011:article/2252862024-03-11T13:10:38Z2024-03-11T13:10:38ZA brief guide to birdwatching in the age of dinosaurs<p>Have you ever wondered what it would be like travel back in time to the age of dinosaurs? If you stumble upon a time machine, remember to bring your binoculars. Birdwatching is a popular hobby today, with an around <a href="https://www.wwt.org.uk/news-and-stories/blog/get-into-birdwatching/#:%7E:text=Bird%20watching%20in%20the%20UK,that%20we%20look%20after%20them.">3 million participants</a> in the UK alone, and in our modern world there are a staggering <a href="https://www.publish.csiro.au/pc/pdf/PCv27_BR4">11,000 species</a> of birds to spot. </p>
<p>Despite the popularity of their modern-day descendants, we often forget about ancient birds because of their more famous dinosaur cousins.</p>
<p>Birds are actually <a href="https://www.nhm.ac.uk/discover/how-dinosaurs-evolved-into-birds.html">a type of dinosaur</a>. They are closely related to smaller, agile meat-eating dinosaurs such as the <em>Velociraptor</em>. Ancient birds came in a variety of forms, from ones with teeth and claws to species barely distinguishable from farmyard <a href="https://www.nature.com/articles/d41586-020-00766-2">chickens</a>. </p>
<p>So, if you were to point your binoculars over the heads of <em>Triceratops</em> and <em><a href="https://theconversation.com/five-things-you-probably-have-wrong-about-the-t-rex-220011">Tyrannosaurus rex</a></em>, what could you spot? Here is a quick introduction to six of the most interesting ancient bird species. </p>
<h2><em>Archaeopteryx</em></h2>
<p><em>Archaeopteryx</em> is <a href="https://www.nhm.ac.uk/discover/dino-directory/archaeopteryx.html">the iconic “dino-bird”</a> from the Jurassic period. The discovery of <em>Archaeopteryx</em> fossils in Germany over 150 years ago provided scientists with the first clues about the link between dinosaurs and modern birds. </p>
<p>At first glance, the skeleton of <em>Archaeopteryx</em> is just like any other meat-eating dinosaur – sharp teeth, clawed hands and a long bony tail. Surrounding the skeleton of specimens such as the <a href="https://www.museumfuernaturkunde.berlin/en/about/news/archaeopteryx-named-fossil-year">Berlin <em>Archaeopteryx</em></a> (discovered between <a href="https://artsandculture.google.com/story/archaeopteryx-lithographica-%E2%80%93-the-berlin-specimen-museum-fuer-naturkunde-berlin/1AVxj85ySOZ4JQ?hl=en">1874 and 1876</a>) however, are imprints of feathers which form a pair of distinctly bird-like wings.</p>
<figure class="align-center ">
<img alt="3D rendering of black bird-like dinosaur flying through the sky" src="https://images.theconversation.com/files/580391/original/file-20240307-21-8fm1ve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580391/original/file-20240307-21-8fm1ve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580391/original/file-20240307-21-8fm1ve.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580391/original/file-20240307-21-8fm1ve.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580391/original/file-20240307-21-8fm1ve.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580391/original/file-20240307-21-8fm1ve.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580391/original/file-20240307-21-8fm1ve.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">
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<span class="caption"><em>Archaeopteryx</em> looked half way between a dinosaur and a modern bird.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/archaeopteryx-birdlike-dinosaur-flying-through-sky-1722734977">Dotted Yeti/Shutterstock</a></span>
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<p>But for many years, palaeontologists debated whether <em>Archaeopteryx</em> could have used these wings to fly. Scientists now think it is likely that <em>Archaeopteryx</em> could have flown, but only <a href="https://www.nature.com/articles/s41467-018-03296-8">in short bursts </a>, like a pheasant. Recent technological advances have given us our first insights into dinosaur colour and studies of fossilised, pigmented cells have shown that <em>Archaeopteryx</em> had <a href="https://www.nature.com/articles/s41598-020-65336-y">matt black</a> wing feathers.</p>
<h2><em>Confuciusornis</em></h2>
<p>This crow-sized bird had a beak like that of modern-day birds, but still had large, <a href="https://digitallibrary.amnh.org/items/fc74de43-ec0e-497f-a199-7f89b6b658b9">dinosaur-like claws</a> on its hands. It is thought that they lived in flocks, large numbers of which were killed by ash or gas in <a href="https://www.nature.com/articles/ncomms4151">volcanic eruptions</a> and preserved as fossils. Known from over <a href="https://www.researchgate.net/publication/326059155_A_taxonomical_revision_of_the_Confuciusornithiformes_Aves_Pygostylia">1,000 fossil specimens</a> from China, <em>Confuciusornis</em> is one of the most common fossil bird species.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/580395/original/file-20240307-30-nefob5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Outline of dinosaur clearly preserved in rock" src="https://images.theconversation.com/files/580395/original/file-20240307-30-nefob5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580395/original/file-20240307-30-nefob5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580395/original/file-20240307-30-nefob5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580395/original/file-20240307-30-nefob5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580395/original/file-20240307-30-nefob5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580395/original/file-20240307-30-nefob5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580395/original/file-20240307-30-nefob5.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>
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<span class="caption"><em>Confuciusornis sanctus</em> fossil, encased in rock.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/dinosaur-fossil-confuciusornis-sanctus-rock-1232355214">Chawalit Chankhantha/Shutterstock</a></span>
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<p>Some of these birds had a <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsbl.2008.0409?casa_token=dLetzDz5OIUAAAAA%3AKUyu-cMBlflBhPXtC6xu-PxSc6wFebScqXzE3LBa33EmqsrzLISDWi08ToliVPfTfyuuDI_psxm7fBY">pair of tail feathers</a> longer than their body, while others lacked these long feathers and would have looked comparatively stumpy. Scientists think these long-tailed birds were the males of the species and those with <a href="https://www.nature.com/articles/ncomms2377">short tails were females</a>. Like modern peacocks and peahens, the males probably used their extravagant tail feathers to woo the females.</p>
<h2><em>Falcatakely</em></h2>
<p>Discovered in 2020, <em><a href="https://www.nature.com/articles/s41586-020-2945-x">Falcatakely</a></em>, from Madagascar, would have resembled a small, buck-toothed toucan. Its oversized, banana-shaped bill only had teeth <a href="https://www.nature.com/articles/d41586-020-03260-x">at the very tip</a>. Although we don’t know what this buck-toothed bird would have eaten, its close relatives ate a <a href="https://www.biorxiv.org/content/10.1101/2023.07.18.549506v2.abstract">variety of food</a>, including fruit, fish and even larger prey. </p>
<p>Scientists think that birds such as <em>Falcatakely</em> could fly the same day they <a href="https://www.science.org/doi/full/10.1126/science.1100000">hatched from their egg</a>, unlike birds today which spend their first weeks or months helpless in the nest.</p>
<h2><em>Hesperornis</em></h2>
<p>One of the weirdest birds from the age of dinosaurs, <em>Hesperornis</em> would have looked something like a six-foot-tall penguin with a beak full of <a href="https://link.springer.com/article/10.1186/s12862-016-0753-6#Sec27">sharp teeth</a>. Its <a href="https://www.mdpi.com/1424-2818/14/4/267">tiny arms</a> would have made T rex look like a weightlifter, so it definitely couldn’t have used them to fly. </p>
<figure class="align-center ">
<img alt="Illustration of bird with tiny wings perched on a rock" src="https://images.theconversation.com/files/580394/original/file-20240307-18-16mtuh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580394/original/file-20240307-18-16mtuh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580394/original/file-20240307-18-16mtuh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580394/original/file-20240307-18-16mtuh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580394/original/file-20240307-18-16mtuh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580394/original/file-20240307-18-16mtuh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580394/original/file-20240307-18-16mtuh.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">
<figcaption>
<span class="caption"><em>Hesperornis</em> was an aquatic bird that lived at the time of the dinosaurs.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/hesperornis-aquatic-bird-that-lived-time-1118302547">Daniel Eskridge/Shutterstock</a></span>
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<p>Instead, <em>Hesperornis</em> used its oversized <a href="https://www.sciencedirect.com/science/article/pii/S0031018217307149">feet to propel</a> itself through the water like a modern cormorant. Out of the water, <em>Hesperornis</em> walked <a href="https://www.sciencedirect.com/science/article/pii/S0031018217307149">awkwardly upright</a> and probably couldn’t travel far overland.</p>
<h2><em>Vegavis and Asteriornis</em></h2>
<p>Towards the end of the dinosaurs’ reign, the earliest groups of modern birds began to appear. The first of these birds to be discovered was <em><a href="https://www.nature.com/articles/nature03150">Vegavis</a></em> from Antarctica, which in the time of dinosaurs would have been <a href="https://www.sciencedirect.com/science/article/pii/S0031018201004527">covered in trees</a> rather than ice. </p>
<p>It was probably an ancestor of ducks and geese and one exceptional fossil of <em>Vegavis</em> even has a rare <a href="https://www.nature.com/articles/nature19852">preserved vocal organ</a>. Analysis of this fossil suggested that <em>Vegavis</em> couldn’t make a songbird melody but could have made simple noises such as goose-like honks.</p>
<p>Sixty-six million years ago, not long before the <a href="https://www.pnas.org/doi/abs/10.1073/pnas.2006087117">asteroid impact</a>, which caused the extinction of the non-bird dinosaurs, lived <em><a href="https://www.nature.com/articles/s41586-020-2096-0">Asteriornis</a></em>. This quail-sized bird from Belgium was an ancestor of modern ducks and chickens. Although it would have looked unremarkable compared to the <a href="https://www.cambridge.org/core/journals/netherlands-journal-of-geosciences/article/stratigraphic-ranges-of-mosasaurs-in-belgium-and-the-netherlands-late-cretaceous-and-cephalopodbased-correlations-with-north-america/2601C3D2DD398B92DFEDA122E82F9991">giant swimming lizards</a> and <a href="https://www.nature.com/articles/s41586-022-05445-y">huge, toothed seagulls</a> it lived alongside, this may have been to its advantage.</p>
<p>Scientists think that the small size of birds such as <em>Asteriornis</em> helped them to survive the <a href="https://academic.oup.com/sysbio/article/67/1/1/3960267">mass extinction</a>. Because smaller animals need less food and take less time to reproduce, these humble birds were able to survive and evolve into the birds you can see through your binoculars today.</p><img src="https://counter.theconversation.com/content/225286/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Abi Crane 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>If you love learning about dinosaurs don’t let crowdpleasers like the T Rex distract you from the fascinating birdlife that once roamed the Earth.Abi Crane, Postgraduate Researcher in Palaeontology, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2200112023-12-19T16:53:46Z2023-12-19T16:53:46ZFive things you probably have wrong about the T rex<figure><img src="https://images.theconversation.com/files/566317/original/file-20231218-17-rt6kdx.jpg?ixlib=rb-1.1.0&rect=36%2C12%2C8142%2C5444&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/adventurous-young-boy-imitating-dinosaur-toy-2124861329">Jacob Lund/Shutterstock</a></span></figcaption></figure><p>An icon from the age of dinosaurs, <em>Tyrannosaurus rex</em> has featured in everything from blockbuster movies to the shape of chicken nuggets. As a creature to be feared for its bone-crushing bite or ridiculed for its inability to give a high five, T rex has captured the imagination of children and adults alike. </p>
<p>One skeleton broke records in 2020 when it sold at auction for <a href="https://www.science.org/content/article/stan-t-rex-sells-record-32-million-auction">US$32 million</a> (£25 million). But how well do you really know T rex? Here is the truth behind five common misconceptions about this dinosaur.</p>
<h2>Myth: T rex had bad eyesight</h2>
<p>Scientists think that T rex had excellent vision, despite what Jurassic Park might have you believe. The <a href="https://www.nature.com/articles/s42003-022-03706-0">grapefruit-sized eyes</a> of T rex could have distinguished objects with up to five times more precision than those of a falcon and <a href="https://www.tandfonline.com/doi/pdf/10.1671/0272-4634(2006)26%5B321%3ABVITD%5D2.0.CO%3B2">13 times better</a> than a human. </p>
<p>They also had <a href="https://www.uv.es/pe/2000_1/retinal/text.pdf">superior colour vision</a>. Like birds and crocodiles, T rex could distinguish more colours of the rainbow than humans and see ultraviolet light. Although it makes for good dramatic tension in fiction, standing still would not hide you from a hungry T rex. </p>
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<h2>Myth: Chickens are the direct descendants of T rex</h2>
<p>This myth has its origins in truth. All birds, including chickens, are not only descendants of dinosaurs but <a href="https://evolution-outreach.biomedcentral.com/articles/10.1007/s12052-009-0133-4">are themselves dinosaurs</a>. Birds belong to a lineage of dinosaurs closely related to the raptors (including <em>Velociraptor</em>). </p>
<p>Early birds, such as <a href="https://www.nhm.ac.uk/discover/dino-directory/archaeopteryx.html"><em>Archaeopteryx</em></a>, had wings like modern birds but teeth and long tails like their ancestors. These ancient birds first appeared <a href="https://www.nature.com/articles/nature12168">in the Jurassic period</a>, millions of years before T rex evolved. </p>
<p>Scientists have identified an ancestor of modern ducks and chickens as the quail-sized <a href="https://www.nature.com/articles/s41586-020-2096-0"><em>Asteriornis</em></a>, nicknamed the <a href="https://www.cam.ac.uk/stories/wonderchicken">wonderchicken</a> by scientists. It was still living at the time of T rex. A handful of these humble bird species <a href="https://www.sciencedirect.com/science/article/pii/S0960982218305347">survived the mass extinction</a> that killed their dinosaur relatives and evolved into all the birds we know today.</p>
<p>T rex, rather than being the grandparent of the modern chicken, is more like an oversized cousin to all birds.</p>
<h2>Myth: T rex had tiny, useless arms</h2>
<p>Muscle reconstructions show that T rex arms <a href="https://www.researchgate.net/profile/Kenneth-Carpenter-2/publication/314895700_Looking_again_at_the_forelimbs_of_Tyrannosaurus_rex/links/58c70de0aca27232ac8297b6/Looking-again-at-the-forelimbs-of-Tyrannosaurus-rex.pdf">were strong</a> for their size and had a reasonable range of motion. It is likely they were used in a range of behaviour. </p>
<p>The <a href="https://www.eaapublishing.org/journals/index.php/biosis/article/view/60">most plausible suggestions</a> scientists have come up with so far include slashing and holding onto prey and use in communicating between T rex individuals.</p>
<p>T rex actually <a href="https://link.springer.com/article/10.1007/BF03043773">couldn’t twist its arms</a> to make its hands face palm downward, as is commonly depicted. To improve the accuracy of your next T rex impression, face your palms towards each other, as if clapping. </p>
<p>At around one metre long, T rex arms are larger than human arms but still small compared with their 13-metre long bodies. Small arms are common among larger theropods (two-legged, predatory dinosaurs) and have <a href="https://www.sciencedirect.com/science/article/pii/S0960982222008600">evolved several times</a> in this group. Other dinosaurs in this group had even smaller arms. </p>
<p>The eight-metre long <a href="https://www.nhm.ac.uk/discover/dino-directory/carnotaurus.html"><em>Carnotaurus</em></a>, a horned predator from South America, had <a href="https://www.sciencedirect.com/science/article/abs/pii/S0024408298901935">stubby arms</a> less than 50 centimetres long. </p>
<h2>Myth: T rex lived alongside <em>Stegosaurus</em></h2>
<p>The age of dinosaurs was probably longer than you think. T rex lived at the end of the Cretaceous period, just before the dinosaur-killing <a href="https://www.pnas.org/doi/abs/10.1073/pnas.2006087117">asteroid strike</a> 66 million years ago. <a href="https://www.nhm.ac.uk/discover/dino-directory/stegosaurus.html"><em>Stegosaurus</em></a>, and other popular Jurassic dinosaurs such as <a href="https://www.nhm.ac.uk/discover/dino-directory/diplodocus.html"><em>Diplodocus</em></a>, lived around 150 million years ago. </p>
<p>T rex lived closer to the modern day than to the time of <em>Stegosaurus</em>. By the time T rex walked the Earth, <em>Stegosaurus</em> were already fossils beneath their feet.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/566315/original/file-20231218-21-hst1i7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Kids food dinosaur shapes on a plate" src="https://images.theconversation.com/files/566315/original/file-20231218-21-hst1i7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566315/original/file-20231218-21-hst1i7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=403&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566315/original/file-20231218-21-hst1i7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=403&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566315/original/file-20231218-21-hst1i7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=403&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566315/original/file-20231218-21-hst1i7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=506&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566315/original/file-20231218-21-hst1i7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=506&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566315/original/file-20231218-21-hst1i7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=506&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">The T rex lived long after stegosaurus went extinct.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/kids-food-dinosaur-shaped-chicken-fish-1427323466">Erhan Inga/Shutterstock</a></span>
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<h2>Myth: T rex was scaly and grey or green</h2>
<p>The idea that T rex might have had feathers is contentious, even among palaeontologists. There is evidence of feathers in many dinosaur species, leading some scientists to conclude that feathers were <a href="https://www.science.org/doi/full/10.1126/science.1235463">widespread among dinosaurs</a>. <a href="https://www.nature.com/articles/nature10906"><em>Yutyrannus</em></a>, a nine-metre long relative of T rex, was found preserved with a coat of fuzzy feathers. </p>
<p>So does this mean T rex was also fluffy? Not so fast. Some scientists think that a full feather coat would leave the giant, warm-blooded T rex at risk of overheating. </p>
<p>This thinking is supported by <a href="https://royalsocietypublishing.org/doi/full/10.1098/rsbl.2017.0092">preserved patches of skin</a> found from many parts of the body that appear to be scaled. Although we don’t know for certain either way, the real T rex was probably something between fully scaly and fully fuzzy. </p>
<p>The science of dinosaur colour is one of the most <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev-earth-073019-045641">exciting developments</a> in recent palaeontology. Scientists have been able to determine the colours and patterns of some exceptionally well preserved dinosaurs by studying fossilised pigement-containing capsules within cells in feathers and scales. </p>
<p>Although no one has worked out what colour T rex was yet, we now know that dinosaurs came in a range of colours, including <a href="https://www.science.org/doi/full/10.1126/science.1186290">red</a> and <a href="https://www.science.org/doi/10.1126/science.1213780">iridescent black</a>, and patterns <a href="https://www.nature.com/articles/nature08740">such as stripes</a>.</p><img src="https://counter.theconversation.com/content/220011/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Abi Crane 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>Impress your niece or nephew with these T rex facts.Abi Crane, Postgraduate Researcher, University of SouthamptonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2027612023-03-31T09:37:19Z2023-03-31T09:37:19ZTyrannosaurus rex: our new research shows it covered its enormous teeth with lips<figure><img src="https://images.theconversation.com/files/518435/original/file-20230330-28-gk7yku.jpg?ixlib=rb-1.1.0&rect=0%2C41%2C6989%2C4872&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Mark Witton</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Picture a <em>Tyrannosaurus rex</em>, that ferocious yet one of the most beloved dinosaurs. Most people will probably imagine a scaly giant with enormous fangs, visible even when its mouth is closed. </p>
<p>This is the image of toothy predatory dinosaurs that popular culture has perpetuated for over 30 years.</p>
<p>But our new study, <a href="http://www.science.org/doi/10.1126/science.abo7877">published in Science</a>, suggests that even the giant teeth of <em>Tyrannosaurus</em> would have been sheathed in scaly lips.</p>
<p>Palaeontologists and artists have held different opinions on how dinosaur faces looked since we began <a href="https://theconversation.com/crystal-palace-dinosaurs-how-we-rediscovered-five-missing-sculptures-from-the-famous-park-182573">recreating their form in the 1830s</a>. From the 1980s onwards, artists and scientists have <a href="https://www.nhbs.com/paleoart-visions-of-the-prehistoric-past-1830-1980-book">mostly shown theropod dinosaurs</a> (the lineage that includes <em>Tyrannosaurus</em>, <em>Velociraptor</em> and birds) with lipless mouths and exposed teeth. </p>
<p>This look became deeply rooted in popular culture thanks to the 1993 film Jurassic Park and its iconic depiction of <em>T. rex</em>. Jurassic Park’s creators deliberately exaggerated the size and visibility of their tyrant’s teeth, despite being an otherwise accurate recreation of <em>Tyrannosaurus</em> for the time. No specific study or fossil discovery inspired this look. The widespread adoption of the lipless dinosaur reflected a preference for a new, ferocious-looking aesthetic rather than a scientific re-think.</p>
<p>This is not to say that lipless theropods are scientifically baseless. Living cousins of dinosaurs, <a href="https://www.ucl.ac.uk/museums-static/obl4he/vertebratediversity/crocodilians.html">the crocodylians</a> (crocodiles and alligators), and the only surviving dinosaur group, birds, both have hard, immobile tissue around their jaws rather than the scaly lips of lizards. So it was reasonable to infer that extinct animals related to crocodylians and birds (including all predatory dinosaurs) had lipless faces. </p>
<figure class="align-center ">
<img alt="Series of Tyrannosaurus portraits: a skull, a green lipless face, a brown lipped face, and a grey-green face with open mouth partially gum-covered teeth." src="https://images.theconversation.com/files/518034/original/file-20230328-5475-muzfsm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518034/original/file-20230328-5475-muzfsm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1039&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518034/original/file-20230328-5475-muzfsm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1039&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518034/original/file-20230328-5475-muzfsm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1039&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518034/original/file-20230328-5475-muzfsm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1306&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518034/original/file-20230328-5475-muzfsm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1306&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518034/original/file-20230328-5475-muzfsm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1306&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The varying faces of <em>Tyrannosaurus rex</em>. The bottom picture is the most accurate, according to new research.</span>
<span class="attribution"><span class="source">Mark P. Witton</span></span>
</figcaption>
</figure>
<p>Our new study, 11 years in the making, brings new data to this conversation. My team analysed theropod fossils and compared them with living reptiles. We found that predatory dinosaurs probably had lips like those you’d find on a lizard.</p>
<p>One part of our research looked at tooth damage. Exposed teeth show greater wear than those behind lips – for example, crocodylians have <a href="https://www.nhm.ac.uk/discover/news/2014/may/museum-opens-wide-giant-crocodile-tooth.html">significant abrasion on their outer teeth</a>. But when we examined theropod teeth using microscopes and compared them with crocodylian teeth, we found theropod teeth were considerably less damaged. </p>
<p>This is not the only difference between theropods and crocodylians. All reptiles have small holes <a href="https://www.britannica.com/animal/reptile/Skull-and-dentition">in their jaw bones</a> that house blood vessels and nerves for their oral skin and gums, usually just millimetres wide. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/518436/original/file-20230330-23-ymidnh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A T-Rex with closed lips" src="https://images.theconversation.com/files/518436/original/file-20230330-23-ymidnh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/518436/original/file-20230330-23-ymidnh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518436/original/file-20230330-23-ymidnh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518436/original/file-20230330-23-ymidnh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518436/original/file-20230330-23-ymidnh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518436/original/file-20230330-23-ymidnh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518436/original/file-20230330-23-ymidnh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Don’t be fooled by those lips.</span>
<span class="attribution"><span class="source">Mark Witton</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Lipped reptiles, lizards and <a href="https://animals.sandiegozoo.org/animals/tuatara">tuataras</a> (the last survivors of a group of lizard-like reptiles from the age of dinosaurs), have relatively few of these holes and they are mostly positioned close to their teeth. <a href="https://core.ac.uk/reader/81671420">Crocodylian skulls</a>, however, are covered in hundreds of tiny openings that are related to their sensitive, tight facial skin.</p>
<p>We found theropod jaw bones are more like lizards’ and have a low number of openings close to their jaw margins. This is also true of crocodylians’ ancient, extinct relatives. This implies that the unusual facial anatomy of living crocodylians evolved within their own lineage, not as a shared feature with the dinosaur/bird line.</p>
<p>We also looked at tooth size, because some predatory dinosaurs had much bigger teeth than any living reptiles, and this might have prevented them from being enveloped inside lips. We calculated a ratio of tooth height and skull length for theropods. Then we compared this with the same value for monitor lizards, the lipped group that includes the only living animal comparable to large theropods in its feeding habits, the komodo dragon. </p>
<p>Our comparisons revealed that no predatory dinosaurs – even the big-toothed <em>T. rex</em> – had teeth larger than living lizards. Indeed, species like the crocodile monitor have proportionally larger teeth than any theropod, so there’s no reason to think dinosaur teeth were too big to be covered by lips.</p>
<p>Finally, we modelled the mechanics of how lipless theropod jaws would close, and found it impossible for some theropods to seal their mouths without lips. The best we could manage was a gappy smile. Forcing jaws into a full seal either crushed jaw-supporting bones or dislocated the jaw joint. With permanently open mouths, these theropods would have faced issues with their oral health and risked dehydration. </p>
<p>Collectively, these studies point to the same conclusion: that theropod mouth anatomy and functionality seems more like that of lizards than crocodiles. This suggests that lizard-like lips covered their teeth.</p>
<p>If we’re right, and lizards are our best model for theropod mouths, dinosaur lips were probably not muscular, <a href="https://theses.gla.ac.uk/77121/">like mammal lips</a> are. So, dinosaurs probably couldn’t snarl like they sometimes do in the movies. </p>
<p>In further contrast with Hollywood’s dinosaurs, we also need to give theropods bigger gums. Unlike crocodiles or even mammals, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3458625/">lizard-line reptiles</a> tend to have large gums that cover some or all of their tooth crowns, even when their teeth are adapted for ripping flesh. This has the effect of making their teeth look smaller or even invisible in their open mouths.</p>
<p>Combined with scaly lips, our findings suggest that predatory dinosaurs may have had softer-looking faces and mouths than we’re used to. But don’t let this fool you. Behind those lips and gums were the same formidable, flesh-rending teeth.</p><img src="https://counter.theconversation.com/content/202761/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark P. Witton 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>Although we’re used to seeing lipless dinosaur carnivores, our new data suggests they had lizard-like lips and probably couldn’t snarl.Mark P. Witton, Research Fellow in Palaeontology, University of PortsmouthLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1886782022-08-25T19:03:08Z2022-08-25T19:03:08ZBig head, small arms: A newly discovered gigantic dinosaur evolved in a similar manner to ‘Tyrannosaurus rex’<figure><img src="https://images.theconversation.com/files/480857/original/file-20220824-7032-zql1sf.jpeg?ixlib=rb-1.1.0&rect=0%2C11%2C998%2C726&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">At 50 years old when it died, a newly discovered dinosaur is one of the oldest on record.</span> <span class="attribution"><span class="source">(Jorge A. Gonzales)</span>, <span class="license">Author provided</span></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/big-head--small-arms--a-newly-discovered-gigantic-dinosaur-evolved-in-a-similar-manner-to-tyrannosaurus-rex" width="100%" height="400"></iframe>
<p>The fossil record represents an amazing window into the endless forms of life that have existed across countless ages. By studying ancient species and ecosystems we can increase our understanding of what lived in the past and how the Earth was different compared to today. We can also use fossils to understand how evolution works and what is most likely to evolve under particular sets of circumstances. </p>
<p>This context is what makes <em>Meraxes gigas</em>, <a href="https://doi.org/10.1016/j.cub.2022.05.057">a newly named theropod dinosaur</a>, so important for our understanding of dinosaur evolution and biodiversity.</p>
<p>I was part of the international team of palaeontologists, led by Juan Canale of the Ernesto Bachmann Palaeontological Museum, that named and described <em>Meraxes gigas</em>. The specimen was collected between 2012 and 2014 near Villa El Chocón in Argentina, in rocks of the ~95 million year old <a href="https://dino-data.ca/cityinfocard.php?ID=8">Huincul Formation</a>. </p>
<h2>Top predator</h2>
<p><em>Meraxes</em> is a large theropod, the group of bipedal, often meat-eating, dinosaurs which also includes birds, and a member of the Carcharodontosauridae family, making it a relative of dinosaurs like <em>Carcharodontosaurus</em>, <em>Giganotosaurus</em> and <em>Acrocanthosaurus</em>. </p>
<p>The discovered specimen is approximately 11 metres long, and its weight is estimated as approximately 4,200 kg. It has a proportionally large skull featuring a rather fearsome set of teeth, along with long legs and large clawed feet, a powerful tail, and small arms and hands. </p>
<p>Likely a top predator, it co-occurred with other large theropods like <a href="https://doi.org/10.1007/s00114-008-0487-4"><em>Skorpiovenator</em></a>, alongside <a href="https://doi.org/10.1016/j.cretres.2003.10.005">large herbivorous sauropod dinosaurs and smaller iguanadontian ornithopod dinosaurs</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/480638/original/file-20220823-24-h3k1yj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="diagram of Meraxes skeleton, with cutout photographs of bones from the specimen" src="https://images.theconversation.com/files/480638/original/file-20220823-24-h3k1yj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480638/original/file-20220823-24-h3k1yj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=388&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480638/original/file-20220823-24-h3k1yj.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=388&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480638/original/file-20220823-24-h3k1yj.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=388&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480638/original/file-20220823-24-h3k1yj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=487&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480638/original/file-20220823-24-h3k1yj.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=487&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480638/original/file-20220823-24-h3k1yj.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=487&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 skeletal diagram of Meraxes gigas, highlighting known bones.</span>
<span class="attribution"><span class="source">(Juan Canale/Ernesto Bachmann Palaeontological Museum)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Distant relatives</h2>
<p><em>Meraxes</em> is particularly notable in what it tells us about the evolution of large size in dinosaurs. Its body plan — a large head and small arms — is very similar to that seen in tyrannosaurids like <em>Tyrannosaurus rex</em>, and abelisaurids like <em>Carnotaurus</em>. </p>
<p>These three groups of theropod dinosaurs are all distant relatives. Each independently evolved both large body size and the combination of a large head and small arms. </p>
<p>We analyzed the evolution of these changes in these three groups by examining changes in arm size relative to other body measurements, such as leg and body size. We found that not only did each group experience similar changes through evolution, but there appears to be a lower limit for how small the arms can be relative to the rest of the body. This may represent a developmental or mechanical constraint: the arm can only get so small relative to the body, regardless of other evolutionary pressures in this context. </p>
<p>There are several potential explanations for the size of the arms; the forelimbs themselves may have retained some function despite their reduced size. Our data most directly support the idea that arm reduction in these dinosaur groups is more likely tracking other traits <a href="https://doi.org/10.1098/rspb.1979.0086">rather than being the subject of evolutionary selective pressure itself</a>. In other words, as the relative size of the skull increased over evolution, the arms decreased proportionally in size as an evolutionary trade-off.</p>
<h2>Growth charts</h2>
<p>Another important thing <em>Meraxes</em> can tell us about dinosaur evolution concerns its growth and age. As a palaeontologist, one of my areas of expertise is in using bone microstructure to understand growth in extinct animals like dinosaurs. I also study how bone growth <a href="https://doi.org/10.1098/rsbl.2021.0383">varies across individuals within and between species</a>. </p>
<p>This involves cutting a bone in half (typically one of the long bones of the hind limb, like a femur or tibia), mounting a piece to a slide, and grinding that piece down to be thin enough that you can pass light through it and view the bone microstructure using a microscope. </p>
<p>From here, changes in bone tissue can be observed, telling us about physiology and relative maturity. We can also see annual growth marks, similar to tree rings. By counting these growth marks, measuring their positions across the bone and analyzing them using statistical growth models, we can estimate not only how much an animal grew from year to year, but also how old it was when it died. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/480640/original/file-20220823-23-h7rjyy.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a microscopic image of bone that looks like clusters of brown circles with dark centres " src="https://images.theconversation.com/files/480640/original/file-20220823-23-h7rjyy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480640/original/file-20220823-23-h7rjyy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480640/original/file-20220823-23-h7rjyy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480640/original/file-20220823-23-h7rjyy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480640/original/file-20220823-23-h7rjyy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480640/original/file-20220823-23-h7rjyy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480640/original/file-20220823-23-h7rjyy.png?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"></a>
<figcaption>
<span class="caption">Close-up image of the bone microstructure of the fibula of Meraxes gigas, showing the extensive secondary bone growth associated with this animal’s skeletal maturity.</span>
<span class="attribution"><span class="source">(Thomas Cullen)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Using this approach to study <em>Meraxes</em>, we were able to determine that it was likely around 50 years old at death, and its skeleton had stopped growing about four years before it died. This would make it the oldest non-avian theropod dinosaur currently known, and one of the oldest known dinosaurs. </p>
<p>We also discovered that <em>Meraxes</em>, <a href="https://doi.org/10.1098/rspb.2020.2258">compared to other gigantic theropods like <em>Tyrannosaurus</em></a>, reached a large size through very different changes to their growth. <em>Meraxes</em> continued growing for a longer period of time when compared to its smaller relatives. <em>Tyrannosaurus</em> had a greater relative growth rate than smaller tyrannosaurid species, but reached adult size in a similar amount of time. </p>
<h2>Independent evolution</h2>
<p>As a result, <em>Meraxes</em> and <em>Tyrannosaurus</em> provide a complex example of evolutionary convergence: they both reached very large size when compared to their relatives, and independently evolved the combination of large skulls and small arms. But they achieved this through very different modifications to their growth pattern through life. </p>
<p>As we continue to study <em>Meraxes</em> and other dinosaurs, we’ll further increase our understanding of the amazing biodiversity and changes throughout the Earth’s history. And in doing so, we’ll also gain a greater understanding of the mechanisms of evolution itself.</p><img src="https://counter.theconversation.com/content/188678/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thomas Cullen has received research grants & funding support from the Natural Sciences and Engineering Research Council of Canada (NSERC), the Dinosaur Research Institute (DRI), and the Kenneth C. Griffin Charitable Fund. </span></em></p>A newly discovered dinosaur has small arms and a large head, similar to Tyrannosaurus rex. Estimated to have died at 50 years old, it’s also one of the oldest individual dinosaurs on record.Thomas Cullen, Postdoctoral Fellow, Earth Sciences, Carleton UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1808522022-04-10T13:09:47Z2022-04-10T13:09:47ZThe discovery of two giant dinosaur species solves the mystery of missing apex predators in North America and Asia<figure><img src="https://images.theconversation.com/files/456981/original/file-20220407-26-cwi93t.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5955%2C3350&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Tyrannosaurus Rex was the top predator in North America just before dinosaurs went extinct at the end of the Cretaceous Period.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/the-discovery-of-two-giant-dinosaur-species-solves-the-mystery-of-missing-apex-predators-in-north-america-and-asia" width="100%" height="400"></iframe>
<p>The top predator of the <a href="https://doi.org/10.1038/ncomms3827">Jurassic and Cretaceous landscapes was usually a species of meat-eating dinosaur</a>. These predators walked on two legs, had powerful jaws lined with sharp teeth and included species from groups known as <a href="https://doi.org/10.1126/science.1193304">tyrannosaurs</a>, <a href="https://doi.org/10.1111/1755-6724.13328">spinosaurs</a> and <a href="https://doi.org/10.1098/rsos.210923">carcharodontosaurs</a>.</p>
<p><em>Tyrannosaurus rex</em>, the goat-eating, jeep-chasing tyrannosaur from the movie <em>Jurassic Park</em>, was the apex predator of <a href="https://www.nhm.ac.uk/discover/dino-directory/tyrannosaurus.html">North America just before dinosaurs went extinct at the end of the Cretaceous Period</a>. Although iconic, <em>T. rex</em> was only one species of many large, meat-eating dinosaurs that dominated various ecosystems at different times over the 130 million years of dinosaur reign.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Rc_i5TKdmhs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The infamous scene from the 1993 movie <em>Jurassic Park</em>, where the T. rex escapes its paddock.</span></figcaption>
</figure>
<p>During the Cretaceous Period, most species of top predator that evolved in North America and Asia were either carcharodontosaurs (shark-toothed dinosaurs) or tyrannosaurs (tyrant dinosaurs). The earlier part of the Cretaceous was ruled by carcharodontosaurs, after which tyrannosaurs replaced them as the top predators until the end of the Cretaceous.</p>
<h2>New species</h2>
<p>Recently two new species of these large Cretaceous predators were discovered — a <a href="https://doi.org/10.1016/j.cretres.2020.104388">tyrannosaur from Canada</a> and a <a href="https://doi.org/10.1098/rsos.210923">carcharodontosaur from Uzbekistan</a>. I was lucky enough to be involved in the study of both. These two discoveries, although unrelated, have some interesting parallels.</p>
<p>In 2019, paleontologists Jared Voris and Kohei Tanaka — both who had trained in <a href="https://ucalgary.ca/dinosaur-paleontology">my lab at the University of Calgary</a> — visited museums to look at fossils housed in collections. Voris went to the Royal Tyrrell Museum in Drumheller, Alta., and Tanaka to the State Geological Museum in Uzbekistan.</p>
<p>Each found a fossil specimen they thought may have been important, although overlooked. Both fossils had been found in Cretaceous age rocks of their respective region, and had sat in the museum collections for at least a decade without much notice.</p>
<p>After many months of study, each of these fossils turned out to be an entirely new species of meat-eating dinosaur, previously unknown to science. This meant that we would need to formally describe them, and each would be given its own species name.</p>
<p>We named the new tyrannosaur species <em>Thanatotheristes degrootorum</em>, which means “reaper of death.” The name draws inspiration from its predatory role in the 80-million-year-old ecosystem and for the first discoverer of the fossil bones, an Alberta rancher called John DeGroot.</p>
<p>On the other hand, we named the carcharodontosaur species <em>Ulughbegsaurus uzbekistanensis</em> after <a href="https://www.britannica.com/biography/Ulugh-Beg">Ulugh Beg</a>, a historical figure and early astronomer in Uzbekistan.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/456990/original/file-20220407-19-jhgg77.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a carcharodontosaurus skull on display" src="https://images.theconversation.com/files/456990/original/file-20220407-19-jhgg77.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/456990/original/file-20220407-19-jhgg77.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/456990/original/file-20220407-19-jhgg77.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/456990/original/file-20220407-19-jhgg77.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/456990/original/file-20220407-19-jhgg77.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/456990/original/file-20220407-19-jhgg77.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/456990/original/file-20220407-19-jhgg77.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&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 carcharodontosaurus skull on display at the National Museum of Nature and Science in Tokyo.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/xevivarela/7760677388">(Xevi V/flickr)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/unraveling-the-mystery-of-how-dinosaurs-get-their-names-44367">Unraveling the mystery of how dinosaurs get their names</a>
</strong>
</em>
</p>
<hr>
<h2>Top predators</h2>
<p>The two species are known from only a few skull bones, with the remainder of their skeletons completely unknown. The most recognizable bones are from the jaws — the upper and lower jaw of <em>Thanatotheristes</em> and the upper jaw of <em>Ulughbegsaurus</em>.</p>
<p>From the jaws, it was apparent both species were a respectable and similar size. We were able to figure out their body size from these preserved bones. Measuring from the tip of the snout to the end of the tail, both species would have been around eight metres long — the length of the average school bus.</p>
<p>In these two studies, we discovered that <em>Thanatotheristes</em> and <em>Ulughbegsaurus</em> were each, by far, the largest predator of their ecosystems. The previous absence of a large predatory species in either ecosystem before was puzzling, as populations of large plant-eating dinosaurs would likely have grown unchecked, <a href="https://www.nationalgeographic.org/media/wolves-yellowstone/">as in living herbivores</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/457175/original/file-20220408-41161-t014q3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="artist illustration of _Thanatotheristes_ on the left and _Ulughbegsaurus_ on the right" src="https://images.theconversation.com/files/457175/original/file-20220408-41161-t014q3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/457175/original/file-20220408-41161-t014q3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=240&fit=crop&dpr=1 600w, https://images.theconversation.com/files/457175/original/file-20220408-41161-t014q3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=240&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/457175/original/file-20220408-41161-t014q3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=240&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/457175/original/file-20220408-41161-t014q3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=302&fit=crop&dpr=1 754w, https://images.theconversation.com/files/457175/original/file-20220408-41161-t014q3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=302&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/457175/original/file-20220408-41161-t014q3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=302&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 artist’s rendition of Thanatotheristes (left) and Ulughbegsaurus (right) based on the discovered fossils.</span>
<span class="attribution"><span class="source">(Julius Csotonyi)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Most other known predatory species from these ecosystems were small, typically less than three metres long. In fact, the older Uzbekistan ecosystem was also home to a <a href="https://doi.org/10.1073/pnas.1600140113">small tyrannosaur species</a> that was <a href="https://doi.org/10.1098/rsos.210923">dwarfed by the large <em>Ulughbegsaurus</em></a>.</p>
<h2>The rise and demise of top predators</h2>
<p>Around 90 million years ago, <a href="https://doi.org/10.1098/rsos.210923">all carcharodontosaur species went extinct</a> – <em>Ulughbegsaurus</em> was among the last of its kind. Their extinction left a vacancy in North American and Asian ecosystems for new, large predators to evolve and take over. The tyrannosaurs, which for the most part, were knee-high to a carcharodontosaur for tens of millions of years prior, finally made their play.</p>
<p>Somewhere between 90 and 80 million years ago, <a href="https://www.nature.com/articles/s42003-019-0308-7?from=article_link">tyrannosaur species began to evolve towards a larger body size</a>. <em>Thanatotheristes</em> was one of the earliest species of these large tyrannosaurs, living around 80 million years ago in Alberta’s prehistoric past. </p>
<p><em>Thanatotheristes</em> and its kin were among the ancestors that led to even larger tyrannosaur species, like the 12 metre long <em>Tyrannosaurus rex</em>. These large species went on to rule Cretaceous ecosystems of North America and Asia for the last 10 million years before the <a href="https://www.nhm.ac.uk/discover/dinosaur-extinction.html">mass extinction event that wiped out the dinosaurs</a>.</p><img src="https://counter.theconversation.com/content/180852/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Darla K. Zelenitsky receives funding from NSERC. </span></em></p>Two recent discoveries in Alberta and Uzbekistan have identified the top predators in those regions during the Cretaceous period. Fossils that had been in storage for years included the jawbones.Darla K. Zelenitsky, Associate Professor, Dinosaur Paleobiology, University of CalgaryLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1736342022-02-01T13:14:21Z2022-02-01T13:14:21ZDid male and female dinosaurs differ? A new statistical technique is helping answer the question<figure><img src="https://images.theconversation.com/files/443225/original/file-20220128-23-12zgv3p.jpg?ixlib=rb-1.1.0&rect=2%2C14%2C1950%2C1159&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">How can researchers tell if male and female dinosaurs, like the stegosaur, were different?</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Journal.pone.0138352.g001A.jpg#/media/File:Journal.pone.0138352.g001A.jpg">Susannah Maidment et al. & Natural History Museum, London</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>In most animal species, <a href="https://doi.org/10.2307/2407393">males and females differ</a>. This is true for people and other mammals, as well as many species of birds, fish and reptiles. But what about dinosaurs? In 2015, I proposed that variation found in the iconic back plates of stegosaur dinosaurs was <a href="https://doi.org/10.1371/journal.pone.0123503">due to sex differences</a>.</p>
<p>I was surprised by how strongly some of my colleagues <a href="https://doi.org/10.1017/pab.2016.51">disagreed</a>, arguing that differences between sexes, called sexual dimorphism, <a href="https://doi.org/10.2307/2407393">did not exist in dinosaurs</a>.</p>
<p><a href="https://scholar.google.com/citations?user=umU9KBMAAAAJ&hl=en&oi=ao">I am a paleontologist</a>, and the debate sparked by my 2015 paper has made me reconsider how researchers studying ancient animals use statistics. </p>
<p>The limited fossil record makes it hard to declare if a dinosaur was sexually dimorphic. But I and some others in my field are beginning to <a href="https://doi.org/10.1038/d41586-019-00857-9">shift away from traditional black-or-white statistical thinking</a> that relies on p-values and statistical significance to define a true finding. Instead of only looking for yes or no answers, we are beginning to consider the estimated magnitude of sexual variation in a species, the degree of uncertainty in that estimate and how these measures compare to other species. This approach offers a more nuanced analysis to challenging questions in paleontology as well as many other fields of science.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/443076/original/file-20220127-9640-1ercxvu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A very colorful duck standing next to a drab brown duck." src="https://images.theconversation.com/files/443076/original/file-20220127-9640-1ercxvu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/443076/original/file-20220127-9640-1ercxvu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/443076/original/file-20220127-9640-1ercxvu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/443076/original/file-20220127-9640-1ercxvu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/443076/original/file-20220127-9640-1ercxvu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/443076/original/file-20220127-9640-1ercxvu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/443076/original/file-20220127-9640-1ercxvu.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">In many species, like these mandarin ducks, males (left) and females (right) look very different.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Pair_of_mandarin_ducks.jpg">Francis C. Franklin via WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Differences between males and females</h2>
<p><a href="http://dx.doi.org/10.1007/978-3-319-47829-6_433-1">Sexual dimorphism</a> is when males and females of a certain species differ on average in a particular trait – not including their reproductive anatomy. Classic examples are how male deer have antlers and male peacocks have flashy tail feathers, while the females lack these traits.</p>
<p>Dimorphism can also be subtle and unflashy. Often the difference is one of degree, like differences in the average body size between males and females – as in <a href="https://doi.org/10.1007/s12110-012-9130-3">gorillas</a>. In these modest cases, researchers use statistics to determine whether a trait differs on average between males and females.</p>
<h2>The dinosaur dilemma</h2>
<p>Studying sexual dimorphism in extinct animals is fraught with uncertainty. If you and I independently dig up similar fossils of the same species, they are inevitably going to be slightly different. These differences could be due to sex, but they could also be driven by age – <a href="https://www.worldcat.org/title/avian-anatomy-integument/oclc/603445440&referer=brief_results">young birds are fuzzy, adult birds are sleek</a>. They could also be due to genetics unrelated to sex, like eye color in humans.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/437461/original/file-20211214-15-1gmw3ot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two drawings of dinosaurs showing different shaped horns and frills." src="https://images.theconversation.com/files/437461/original/file-20211214-15-1gmw3ot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/437461/original/file-20211214-15-1gmw3ot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=520&fit=crop&dpr=1 600w, https://images.theconversation.com/files/437461/original/file-20211214-15-1gmw3ot.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=520&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/437461/original/file-20211214-15-1gmw3ot.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=520&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/437461/original/file-20211214-15-1gmw3ot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=653&fit=crop&dpr=1 754w, https://images.theconversation.com/files/437461/original/file-20211214-15-1gmw3ot.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=653&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/437461/original/file-20211214-15-1gmw3ot.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=653&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">It’s possible that variation among individual dinosaurs of the same species could be due to sexual dimorphism, but there are rarely good enough samples to assert so using traditional statistics.</span>
<span class="attribution"><span class="source">James Ormiston</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>If paleontologists had thousands of fossils to study of every species, the many sources of biological variation wouldn’t matter as much. Unfortunately, the <a href="https://doi.org/10.1002/bies.201700167">ravages of time</a> have left the fossil record painfully incomplete, often with less than a dozen good specimens for large, extinct vertebrate species. Additionally, there is currently no way to identify the sex of an individual fossil except in rare cases where obvious clues exist, like <a href="https://doi.org/10.1126/science.1110578">eggs preserved within the body cavity</a>. </p>
<p>So where does all this leave the debate on whether male and female dinosaurs had differences within traits? On the one hand, birds – which are direct descendants of dinosaurs – <a href="https://doi.org/10.1098/rspb.1998.0308">commonly show sexual dimorphism</a>. So do <a href="https://doi.org/10.18475/cjos.v45i1.a12">crocodilians</a>, dinosaurs’ next closest living relatives. Evolutionary theory also predicts that, since dinosaurs reproduced with sperm and egg, there would be a <a href="https://doi.org/10.1016/j.tree.2011.12.006">benefit to sexual dimorphism</a>.</p>
<p>These things all suggest that dinosaurs likely were sexually dimorphic. But in science you need to be quantitative. The challenge is that there is little in the way of <a href="https://doi.org/10.1017/pab.2016.51">statistically significant</a> analyses of the fossil record to support dimorphism. </p>
<h2>Statistical shifts</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/443057/original/file-20220127-6424-dz34sy.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A line graph showing two peaks." src="https://images.theconversation.com/files/443057/original/file-20220127-6424-dz34sy.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/443057/original/file-20220127-6424-dz34sy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=315&fit=crop&dpr=1 600w, https://images.theconversation.com/files/443057/original/file-20220127-6424-dz34sy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=315&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/443057/original/file-20220127-6424-dz34sy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=315&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/443057/original/file-20220127-6424-dz34sy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=396&fit=crop&dpr=1 754w, https://images.theconversation.com/files/443057/original/file-20220127-6424-dz34sy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=396&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/443057/original/file-20220127-6424-dz34sy.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">Very large sex differences can create a bimodal distribution that looks like two distinct groupings of a certain measurement.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Bimodal.png">Maksim via WikimediaCommons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>There are a couple of ways paleontologists could test for sexual dimorphism. They could look to see if there are statistically significant differences between fossils from presumed males and females, but there are very few specimens where researchers <a href="https://doi.org/10.1073/pnas.0708903105">know the sex</a>. Another method is to see whether there are two distinct groupings of a trait, called a bimodal distribution, which could suggest a difference between males and females.</p>
<p>To tell whether a perceived difference between two groups is true, scientists have traditionally used a tool called the p-value. P-values quantify the probability of a result being due to random chance. If a p-value is low enough, the result is deemed “statistically significant” and considered unlikely to have happened by chance.</p>
<p>But p-values can be heavily influenced by sample size and the design of the study, in addition to the actual degree of sexual dimorphism. Because of the very small sample size of fossils, relying on this statistical technique makes it exceedingly difficult to categorically proclaim what dinosaur species were dimorphic. </p>
<p>The weakness of the black-or-white approach that focuses solely on whether a result is statistically significant has led to hundreds of scientists <a href="https://doi.org/10.1038/d41586-019-00857-9">calling to abandon significance testing with p-values</a> in favor of something called <a href="https://doi.org/10.1111/j.1469-185X.2007.00027.x">effect size statistics</a>. Using this approach, researchers would simply report the measured difference between two groups and the uncertainty in that measurement.</p>
<h2>Effect size statistics</h2>
<p>I have begun to apply effect size statistics in <a href="https://doi.org/10.1093/biolinnean/blaa105">my research on dinosaurs</a>. My colleagues and I compared sexual dimorphism in body size between three different dinosaurs: the duck-billed <em>Maiasaura</em>, <em>Tyrannosaurus rex</em> and <em>Psittacosaurus</em>, a small relative of <em>Triceratops</em>. None of these species would be expected to show statistically significant size differences between males and females according to p-values. But that approach does not capture the nature of the variation within these species. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/443567/original/file-20220131-15-3xspkd.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A cast of a duck billed dinosaur fossil skeleton." src="https://images.theconversation.com/files/443567/original/file-20220131-15-3xspkd.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/443567/original/file-20220131-15-3xspkd.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/443567/original/file-20220131-15-3xspkd.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/443567/original/file-20220131-15-3xspkd.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/443567/original/file-20220131-15-3xspkd.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/443567/original/file-20220131-15-3xspkd.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/443567/original/file-20220131-15-3xspkd.jpeg?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">Using effect size statistics, researchers were able to determine that the duck-billed dinosaur <em>Maiasaura</em> showed a larger amount of dimorphism with the least uncertainty in that estimate compared to other dinosaurs.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Maiasaura#/media/File:Maiasaura_peeblesorum_cast_-_University_of_California_Museum_of_Paleontology_-_Berkeley,_CA_-_DSC04688.JPG">Daderot via WikimediaCommons</a></span>
</figcaption>
</figure>
<p>When we instead used effect size statistics, we were able to estimate that male and female <em>Maiasaura</em> demonstrate a greater difference in body mass compared to the other two species and that we had a higher confidence in this estimate as well. A few of the characteristics within the data helped reduce the uncertainty. First, we had a large number of <em>Maiasaura</em> fossils, from individuals of various ages. These bones very nicely fit with trajectories of how size changes as an individual grows from juvenile to adult, so we could control for differences due to age and instead focus on differences due to sex.</p>
<p>Additionally, the <em>Maiasaura</em> fossils all come from a <a href="https://doi.org/10.1017/pab.2015.19">single bone bed</a> of individuals that died in the same place at the same time. This means that variation between individuals is likely not due to them being different species from different regions or time periods. </p>
<p>If my colleagues and I had approached the problem expecting a yes or no answer on whether males and females differed in size, we would have completely missed all of these intricacies. Effect size statistics allow researchers to produce much more nuanced and, I think, informative results. It is almost as much a difference in the philosophical approach to science as it is a mathematical one.</p>
<p>Studying dinosaur dimorphism is not the only place p-values create issues. Many fields of science, including <a href="https://theconversation.com/the-replication-crisis-is-good-for-science-103736">medicine and psychology</a>, are having similar <a href="https://doi.org/10.1080/00031305.2018.1543137">debates about issues in statistics</a> and a worrying problem of <a href="https://doi.org/10.1371/journal.pmed.0020124">unrepeatable studies</a>.</p>
<p>Embracing uncertainty in data – rather than looking for black-or-white answers to questions like whether male and female dinosaurs were sexually dimorphic – can help elucidate dinosaur biology. But this shift in thinking may be felt far and wide across the sciences. A careful consideration of problems within statistics could have deep impacts across many fields.</p>
<p>[<em>Understand new developments in science, health and technology, each week.</em> <a href="https://memberservices.theconversation.com/newsletters/?nl=science&source=inline-science-understand">Subscribe to The Conversation’s science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/173634/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Evan Thomas Saitta 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>The lack of large numbers of fossils makes it hard to study sexual dimorphism in dinosaurs. But a new statistical approach offers insight into this question and others across science.Evan Thomas Saitta, Postdoctoral Scholar in Paleontology, University of ChicagoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1632722021-06-29T15:32:01Z2021-06-29T15:32:01ZFossil offers fresh insights into social habits of our non-mammalian ancestors<figure><img src="https://images.theconversation.com/files/408374/original/file-20210625-13-1dlvscj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A reconstruction of face-biting gorgonopsian skulls.</span> <span class="attribution"><span class="source">Sophie Vrard, Creaphi</span></span></figcaption></figure><p>Bite marks, in the form of traces left on bones by the teeth of scavengers or predators, are not uncommon in the fossil record. These marks are sometimes impressively large. What they show is that carnivores of the past, like their modern equivalents, used to eat flesh.</p>
<p>So far, so good.</p>
<p>But every now and then a new find throws open new possibilities. In <a href="https://www.frontiersin.org/articles/10.3389/fevo.2021.699298/full">our paper</a> we unpack a rare find – the first healed bite mark and embedded tooth in the snout of a middle Permian gorgonopsian. The <a href="https://ucmp.berkeley.edu/synapsids/gorgonopsia.html">gorgonopsians</a> were a group of fierce sabre-toothed predators that roamed Africa between 265 million and 250 million years ago. These non-mammalian <a href="https://www.britannica.com/animal/therapsid">therapsids</a> were part of the ancestral stock that eventually <a href="https://theconversation.com/what-fossils-reveal-about-the-hairy-history-of-mammals-ancestors-61449">evolved mammalness</a> and gave rise to modern mammals. </p>
<p>The fossil we described in our research was recently rediscovered in the collection of Cape Town’s <a href="https://www.iziko.org.za/museums/south-african-museum">Iziko Museum of Natural History</a>. The small partial snout was originally found in the 1940s by the famous South African palaeontologist <a href="http://www.worldcat.org/identities/lccn-no2009100095/">Lieuwe D. Boonstra</a>. </p>
<p>In this fossil the bite had healed, leaving a scar – or callus. As bone takes several weeks to heal, the healed bone tells us that the gorgonopsian survived an attack by another predator. Therefore, it appears that the biter lost the tooth during the attack, and the healed bone developed around the tooth for a few weeks before the animal died. </p>
<p>Finding a fossil tooth embedded in bone is always great news for palaeontologists, as it is the gateway to some otherwise out-of-reach understanding of the behaviour of extinct animals. For example, it can demonstrate that the biter had <a href="https://www.jstor.org/stable/40864394">bone-crushing or puncturing capabilities</a>. Palaeontologists have used fossilised teeth embedded in a callus to prove that a carnivorous species had bitten a living prey, and that the prey ran away; this demonstrated that the carnivore was not only scavenging, but was also hunting. This is how in 2013 American palaeontologists managed <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3732924/">to demonstrate</a> that <em>Tyrannosaurus rex</em> was not a scavenger, contrary to the popular belief of the time. </p>
<p>Prior to our <a href="https://doi.org/10.3389/fevo.2021.699298">newly published research</a>, no such embedded fossil tooth had been found in <a href="https://www.britannica.com/animal/therapsid">therapsids</a>. We developed two hypotheses as to what happened here: one, that it was a failed attack, most likely by another carnivorous species. Or two, that it was made by another gorgonopsian during some form of social biting.</p>
<p>To test the predation hypothesis we compared the embedded tooth to those of other animals living at the time. We concluded that although we can’t rule out the predator hypothesis, the <a href="https://theconversation.com/you-can-thank-our-pre-mammalian-ancestors-for-your-sexy-teeth-65663">social signalling</a> hypothesis was more likely. </p>
<p>If our hypothesis is correct it suggests that therapsids were fighting each other during ritualised combats. The practice of social biting for signalling – males sparring for territory, dominance, and access to mates – has long been <a href="https://theconversation.com/how-selfies-and-family-photos-put-300-million-years-of-evolution-on-display-71717">hypothesised in mammalian ancestors</a>, but evidence has been lacking. </p>
<p>Our findings will help fill an important gap in our knowledge of the onset of social behaviour in the lineage that eventually gave rise to mammals. It shows that social interactions are not a new phenomenon that evolved with more intelligent mammals, but had already developed in our small-brained ancestors. It also suggests that we’ve been overlooking evidence – such as bite marks in therapsids – for over a century, so more new discoveries may await.</p>
<h2>Identifying the attacker</h2>
<p>Finding the tip of a tooth embedded in the snout of a gorgonopsian, surrounded by a distinctive callus of healed bone, was puzzling. Gorgonopsians were themselves predators and were thus unlikely to become prey. Did the embedded tooth imply that this gorgonopsian was attacked by a bigger “super predator”?</p>
<p>We concluded that the answer was no because the embedded tooth was not significantly larger than the teeth of the gorgonopsian itself. So, the biter was likely an animal of similar size. </p>
<p>We also wondered whether a prey animal fighting for its life might have lost a tooth in battle with the gorgonopsian. This, too, we excluded: the embedded tooth displayed a sharp, meat-shearing edge, meaning its owner was evidently a carnivore, not prey.</p>
<p>Ultimately, the secret of the attacker’s identity lay not in the tooth, but in the callus. This indicated that the gorgonopsian survived the attack and that the bite was likely not meant to be lethal. By understanding this it became clear that this wasn’t a predator versus prey situation, but a social signal: the attacker was another gorgonopsian making a point.</p>
<h2>Face-biting</h2>
<p>In modern species, fights between males for territory, dominance, and access to mates <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev.ecolsys.39.110707.173502">are common</a>. More often than not, these competitions are non-lethal because they are ritualised and are more about display than physical aggression. The aim is to discourage rather than to kill the opponent. </p>
<figure class="align-center ">
<img alt="Two grey wolves are snarling; one has the other's muzzle in its jaws. The action appears playful rather than vicious." src="https://images.theconversation.com/files/407861/original/file-20210623-25-sa2lcg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/407861/original/file-20210623-25-sa2lcg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/407861/original/file-20210623-25-sa2lcg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/407861/original/file-20210623-25-sa2lcg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/407861/original/file-20210623-25-sa2lcg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/407861/original/file-20210623-25-sa2lcg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/407861/original/file-20210623-25-sa2lcg.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">Wolves in Norway engage in the face-biting behaviour that may have originated as long as 260 million years ago.</span>
<span class="attribution"><span class="source">Wikicommons/Taral Jansen/Soldatnytt from Oslo, Norway/</span></span>
</figcaption>
</figure>
<p>Biting an opponent’s face is often an effective way to gain the upper hand, and face-biting has indeed been reported <a href="https://www.researchgate.net/publication/40662860_Head-biting_behavior_in_theropod_dinosaurs_Paleopathological_evidence">in numerous species</a>. Noticeably, evidence of face-biting has also <a href="https://blogs.scientificamerican.com/laelaps/fighting-saber-toothed-cats-bit-each-other-on-the-face/">been reported</a> in other animals with sabre-like canines, such as the infamous sabre-toothed cats. </p>
<p>Our research suggests that the behaviour of social biting may have originated among mammal ancestors some 260 million years ago. This is another exciting step in understanding our own and other mammals’ ancient behaviours.</p><img src="https://counter.theconversation.com/content/163272/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Julien Benoit receives funding from the DST-NRF Centre of Excellence in Palaeosciences.</span></em></p><p class="fine-print"><em><span>Claire Browning receives funding from the National Research Foundation and is permanently employed at the Iziko South African Museum. </span></em></p><p class="fine-print"><em><span>Luke Norton receives funding from The Palaeontological Scientific Trust (PAST).</span></em></p>Finding a fossil tooth embedded in bone is always great news for palaeontologists, as it is the gateway to some otherwise out-of-reach understanding of the behaviour of extinct animals.Julien Benoit, Senior Researcher in Vertebrate Palaeontology, University of the WitwatersrandClaire Browning, Curator of Karoo Palaeontology, Iziko Museums of South AfricaLuke Norton, Honorary Research Fellow, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1541882021-04-21T08:26:26Z2021-04-21T08:26:26ZFat-footed tyrannosaur parents couldn’t keep up with their skinnier offspring, fossil footprints reveal<figure><img src="https://images.theconversation.com/files/381455/original/file-20210130-18933-t5ob7.png?ixlib=rb-1.1.0&rect=85%2C101%2C1745%2C1005&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Artwork by José Vitor Silva. </span>, <span class="license">Author provided</span></span></figcaption></figure><p><em>Tyrannosaurus rex</em> is perhaps the most famous of all dinosaurs. It and its closest kin, a group referred to as “tyrannosaurs”, have been embedded in popular culture as powerful and mobile predators. </p>
<p>Consider the below scene from the 1993 blockbuster Jurassic Park; an adult <em>T. rex</em> chases down a speeding Jeep — much to the thrill of the audience. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/rxqHVoZ0fzc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The 1993 Jeep chase scene from Jurassic Park remains an iconic movie moment.</span></figcaption>
</figure>
<p>But Jeeps and fanciful theme parks aside, are these depictions realistic? </p>
<p>Our research, <a href="https://www.tandfonline.com/doi/full/10.1080/02724634.2021.1878201">published today</a> in the Journal of Vertebrate Paleontology, shows while young tyrannosaurs may have indeed been the vision of wrath depicted above, they likely became broader-footed, bulky and less mobile in adulthood. </p>
<h2>A new perspective</h2>
<p>Previous arguments about the way tyrannosaurs did (or didn’t) run either focused on their bones, or relied on computer models to simulate their running abilities.</p>
<p>Apart from being smaller, the skeletons of young tyrannosaurs are also more lightly built than their bulkier parents, which suggests they were probably faster and more nimble for their body size. Juveniles tended to have relatively longer legs and smaller skulls, and weighed much <a href="https://www.nature.com/news/2004/040809/full/040809-7.html">less than a fully grown adult</a>. </p>
<p>In fact, the volume of leg muscles needed to sustain a fast running pace in a six-tonne adult <em>T. rex</em> would have probably been <a href="https://www.nature.com/articles/4151018a">biologically impossible</a>. This would require the dinosaur having as much as 86% of its total body weight just as leg muscle!</p>
<p>However, skeletons only represent part of the story. Fossilised footprints provide a unique snapshot in time of how an animal (or species) moved about its environment — one not provided by skeletons. </p>
<p>Fossilised footprints are a fleshed-out image of the feet as they once appeared in real life, with the soft parts still intact. </p>
<p>In 2015 and 2018, our team discovered a new collection of tyrannosaur footprints in rocks at a lonely outpost in western Canada, which we introduce for the first time in our new paper. </p>
<p>These footprints presented a unique opportunity to study how tyrannosaurs’ foot shapes changed from youth to adulthood. If their relative mobility decreased as they grew — as was previously hypothesised from studying their skeletons — then we’d expect this to be expressed in foot shape, too. </p>
<p>Younger and swifter animals would have more slender feet, whereas older individuals would have bulkier feet, less suited for speed and agility. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-many-tyrannosaurus-rex-walked-the-earth-159041">How many _Tyrannosaurus rex_ walked the Earth?</a>
</strong>
</em>
</p>
<hr>
<h2>Tracking ancient footprints through bear country</h2>
<p>The tyrannosaur tracks we found remain preserved in a wilderness area near Grande Prairie in Northwestern Alberta, Canada. The region is known for its bitter cold winters, which causes the rivers to flood in spring as snow-melt rolls off the nearby Rocky Mountains. </p>
<p>The footprints themselves are preserved along a bank of the Redwillow River, surrounded by <a href="https://en.wikipedia.org/wiki/Taiga">Boreal forest</a>, which today is home to wildlife including brown bears, black bears and wolves. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/383674/original/file-20210211-22-1xokosb.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Tracksite in Albert, Canada" src="https://images.theconversation.com/files/383674/original/file-20210211-22-1xokosb.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/383674/original/file-20210211-22-1xokosb.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=355&fit=crop&dpr=1 600w, https://images.theconversation.com/files/383674/original/file-20210211-22-1xokosb.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=355&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/383674/original/file-20210211-22-1xokosb.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=355&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/383674/original/file-20210211-22-1xokosb.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=446&fit=crop&dpr=1 754w, https://images.theconversation.com/files/383674/original/file-20210211-22-1xokosb.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=446&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/383674/original/file-20210211-22-1xokosb.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=446&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Lush forest surrounded the track site where the tyrannosaur footprints were found in Alberta.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Thankfully our close encounters were largely with deer, although swarms of mosquitoes were a constant nuisance. </p>
<p>Tyrannosaur footprints in this area can be identified by the presence of three long and narrow toes, often with sharp, pointed claw marks. We found up to ten footprints, all about 72 million years old, ranging from 30 to 62 centimetres in length. </p>
<p>Although no bones were discovered, the footprints may have belonged to <em>Albertosaurus</em>. This tyrannosaur lived in Alberta at that time and was an earlier and smaller relative of <em>T. rex</em>. </p>
<h2>My, what big heels you have!</h2>
<p>Using a method called geometric morphometrics, we analysed the best tyrannosaur footprints from our collection of tracks, along with previously discovered footprints.</p>
<p>This method mathematically removes the effect of overall size difference between each footprint while examining important differences in footprint shape. </p>
<p>Applied to our samples, we found the main difference across all footprints was the surface area and width of the heel relative to the footprint’s length.</p>
<p>Larger prints had proportionally larger heels while smaller tracks had narrower, smaller heels.</p>
<p>This difference likely relates to the imposing size of an adult tyrannosaur, or specifically an adult <em>Albertosaurus</em>, which may have weighed between <a href="https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/2041-210X.12226">1,300 and 2,200 kg</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/383676/original/file-20210211-22-1up9leq.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Tyrannosaur track growth photo and diagram." src="https://images.theconversation.com/files/383676/original/file-20210211-22-1up9leq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/383676/original/file-20210211-22-1up9leq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=209&fit=crop&dpr=1 600w, https://images.theconversation.com/files/383676/original/file-20210211-22-1up9leq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=209&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/383676/original/file-20210211-22-1up9leq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=209&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/383676/original/file-20210211-22-1up9leq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=263&fit=crop&dpr=1 754w, https://images.theconversation.com/files/383676/original/file-20210211-22-1up9leq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=263&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/383676/original/file-20210211-22-1up9leq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=263&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">On the left is a photo of a tyrannosaur track likely made by a middle-aged <em>Albertosaurus</em>. The diagram on the right shows how tyrannosaur feet may have changed in both shape and size as they aged.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>A wider and more fleshy heel probably helped adults maintain balance and support increased weight, but likely came at the expense of speed and agility. </p>
<p>Our work on footprints serves to support the hypothesis that as tyrannosaurs grew they underwent a shift from quick, sprightly juveniles to slower, heavy-set adults.</p>
<h2>Slowed down by old age</h2>
<p>Would this have been a problem for catching food as an adult tyrannosaur? Probably not. The large four-legged herbivores they hunted, such as <em><a href="https://www.sciencedirect.com/science/article/pii/S0960982213013948">Edmontosaurus regalis</a></em> (which weighed about 4,000kg), were probably even slower.</p>
<p>So what about that chase scene from Jurassic Park? </p>
<p>Well, we still can’t be certain exactly how fast an adult <em>T. rex</em> could run. But we can say heavier and bulkier adults were probably slower for their body size than more slender juveniles. </p>
<p>Perhaps it should have been a juvenile tyrannosaur chasing that Jeep instead. Although, this wouldn’t have been quite as scary. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-could-dinosaurs-evolve-back-into-existence-148623">Curious Kids: could dinosaurs evolve back into existence?</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/154188/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan James Enriquez receives funding from the Australian Government via a Research Training Program scholarship, and the University of New England. </span></em></p><p class="fine-print"><em><span>Nicolas Campione receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Phil Bell receives funding from The Australian Research Council. </span></em></p>So how accurate is the T. rex’s running speed in that famous Jurassic Park jeep-chase scene?Nathan James Enriquez, PhD Student, 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/1590412021-04-16T20:16:33Z2021-04-16T20:16:33ZHow many ‘Tyrannosaurus rex’ walked the Earth?<figure><img src="https://images.theconversation.com/files/395507/original/file-20210416-21-215xck.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2269%2C1437&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">_Tyrannosaurus rex_ spanned all of ancient North America, and about 20,000 lived at once.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/tyrannosaurus-rex-dinosaur-royalty-free-illustration/99311107?adppopup=true">Roger Harris/Science Photo Library vie Getty Images</a></span></figcaption></figure><p><em>The <a href="https://theconversation.com/us/topics/research-brief-83231">Research Brief</a> is a short take about interesting academic work.</em></p>
<h2>The big idea</h2>
<p>During 2.4 million years of existence on Earth, a total of <a href="https://doi.org/10.1126/science.abc8300">2.5 billion <em>Tyrannosaurus rex</em> ever lived</a>, and 20,000 individual animals would have been alive at any moment, according to a new calculation method we <a href="https://doi.org/10.1126/science.abc8300">described in a paper published on April 15, 2021</a> in the journal Science.</p>
<p>To estimate population, our team of <a href="https://scholar.google.com/citations?user=5CGShQUAAAAJ&hl=en&oi=ao">paleontologists</a> and <a href="https://ib.berkeley.edu/labs/marshall/people.php">scientists</a> had to combine the extraordinarily comprehensive existing research on <em>T. rex</em> with an ecological principle that connects <a href="https://doi.org/10.1038/290699a0">population density to body size</a>.</p>
<p>From microscopic growth patterns in bones, researchers inferred that <em>T. rex</em> <a href="https://doi.org/10.1073/pnas.0708903105">first mated at around 15 years old</a>. With growth records, scientists can also generate survivorship curves – an estimate of a <a href="https://doi.org/10.1126/science.1125721"><em>T. rex</em>‘s chances of living to a given age</a>. Using these two numbers, our team estimated that <em>T. rex</em> generations took 19 years. Finally, <em>T. rex</em> existed as a species for <a href="https://doi.org/10.1371/journal.pone.0188426">1.2 to 3.6 million years</a>. With all of this information, we calculate that <em>T. rex</em> existed for 66,000 to 188,000 generations. </p>
<p>From the fossil record alone, we had generated a <em>T. rex</em> turnover rate. If our team could estimate the number of individuals in each generation, we would know how many <em>T. rex</em> ever lived. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/395516/original/file-20210416-13-n5nimm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A drawing of one elephant on the left next to dozens of rabbits on the right." src="https://images.theconversation.com/files/395516/original/file-20210416-13-n5nimm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/395516/original/file-20210416-13-n5nimm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=345&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395516/original/file-20210416-13-n5nimm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=345&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395516/original/file-20210416-13-n5nimm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=345&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395516/original/file-20210416-13-n5nimm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=434&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395516/original/file-20210416-13-n5nimm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=434&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395516/original/file-20210416-13-n5nimm.jpg?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"></a>
<figcaption>
<span class="caption">Damouth’s law connects body mass to population density.</span>
<span class="attribution"><span class="source">Sara Volz</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>In ecology, there is a well-established relationship between body mass and population density called <a href="https://doi.org/10.1038/290699a0">Damuth’s law</a>. Larger animals need more space to survive – one square mile of grassland can support a lot more bunnies than elephants. This relationship is also dependent on metabolism – animals that burn more energy require more space.</p>
<p>Paleontologists have come up with a range of good <a href="https://doi.org/10.1111/brv.12638">estimates of <em>T. rex</em>’s body mass</a> and have also estimated <a href="https://doi.org/10.1073/pnas.0904000106">its metabolism</a> – slower than mammals but somewhat faster than a large modern lizard, the Komodo dragon. With Damuth’s law, we then estimated that the ancient world held about one <em>T. rex</em> every 42.4 square miles (109.9 square km). That’s about two individuals in the entire area of Washington, D.C.</p>
<p>Now we had all the pieces we needed. Multiplying the population density by the area in which <em>T. rex</em> lived gives us an estimate of 20,000 individuals per generation.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/395198/original/file-20210415-17-2ziwwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Thousands of drawn T. rex showing only a small number turning into fossils." src="https://images.theconversation.com/files/395198/original/file-20210415-17-2ziwwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395198/original/file-20210415-17-2ziwwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395198/original/file-20210415-17-2ziwwa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395198/original/file-20210415-17-2ziwwa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395198/original/file-20210415-17-2ziwwa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395198/original/file-20210415-17-2ziwwa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395198/original/file-20210415-17-2ziwwa.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">Knowing the total number of <em>T. rex</em> that ever lived unlocks other pieces of knowledge – like the fraction that turn into fossils and were found.</span>
<span class="attribution"><span class="source">Franz Anthony</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Why it matters</h2>
<p>Once we figured out the average population size, we were able to calculate the fossilization rate for <em>T. rex</em> – the chance that a single skeleton would survive to be discovered by humans 66 million years later. The answer: about 1 in 80 million. That is, for every 80 million adult <em>T. rex</em>, there is only one clearly identifiable specimen in a museum. </p>
<p>This number highlights how <a href="https://doi.org/10.1038/35000558">incomplete the fossil record is</a> and allows researchers to ask how rare a species could be without disappearing entirely from the fossil record.</p>
<p>Beyond calculating the <em>T. rex</em> fossilization rate, our new method could be used to calculate population size for other extinct species.</p>
<h2>What still isn’t known</h2>
<p>Estimates about extinct animals always include some amount of uncertainty. Our estimate of <em>T. rex</em> population density ranges from one individual for every 2.7 square miles (7 square km) to one for every 665.7 square miles (1,724 square km). But surprisingly, the largest source of this uncertainty comes from Damuth’s law. There is a lot of variation in modern animals. For example, Arctic foxes and Tasmanian devils have similar body mass, but devils have six times the population density.</p>
<p>Further study of living animals could tighten up our estimates on <em>T. rex</em>.</p>
<p>We also don’t know fossilization rates of other long extinct dinosaurs. If we have many fossils of one species, does that mean they were more common than <em>T. rex</em>, or do we simply recover their fossils more often? </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/395500/original/file-20210416-19-jbcpr5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A skeleton of T. rex." src="https://images.theconversation.com/files/395500/original/file-20210416-19-jbcpr5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/395500/original/file-20210416-19-jbcpr5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/395500/original/file-20210416-19-jbcpr5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/395500/original/file-20210416-19-jbcpr5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/395500/original/file-20210416-19-jbcpr5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/395500/original/file-20210416-19-jbcpr5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/395500/original/file-20210416-19-jbcpr5.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">The huge amount of research that has been done on <em>T. rex</em> played an important role in making this calculation.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:FMNH_SUE_Trex.jpg#/media/File:FMNH_SUE_Trex.jpg">Evolutionnumber9/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>What’s next</h2>
<p>This study might lead to other hidden facts about <em>T. rex</em> biology and ecology. </p>
<p>For instance, we might be able to learn whether <em>T. rex</em> populations fluctuated up and down with <em>Triceratops</em> – similar to <a href="https://isleroyalewolf.org/data/data/home.html">wolf and moose predator and prey relationships today</a>. However, most other dinosaurs <a href="https://doi.org/10.1371/journal.pone.0016574">do not yet have the incredibly rich data</a> from decades of careful fieldwork that allowed our team to tally up <em>T. rex</em>. </p>
<p>If scientists want to apply this powerful technique to other extinct animals, we’ve got some more digging to do.</p>
<iframe src="https://embed.acast.com/60087127b9687759d637bade/60781590fbe1eb33d652507a?cover=true&ga=false" frameborder="0" allow="autoplay" width="100%" height="110"></iframe>
<p><em><a href="https://theconversation.com/dinosaurs-from-giant-reptiles-to-warm-blooded-feathered-creatures-how-our-understanding-of-what-they-looked-like-has-changed-podcast-158905">The Conversation Weekly podcast</a> digs into new research shedding light on the real size and feathery appearance of dinosaurs.</em></p><img src="https://counter.theconversation.com/content/159041/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>Using the incredible wealth of fossil data and a modern ecological theory, researchers estimated population density for the extinct apex predator.Ashley Poust, Research Associate in Paleontology, University of California, BerkeleyDaniel Varajão de Latorre, Ph.D. Student in Paleontology, University of California, BerkeleyLicensed 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/896152018-01-05T16:00:35Z2018-01-05T16:00:35ZWhy I jumped at the chance to bring the real T. rex to life for TV<figure><img src="https://images.theconversation.com/files/200952/original/file-20180105-26154-1wiqvem.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">BBC/Dom Walter, Tailsmith productions</span></span></figcaption></figure><p>The chance to work on a major documentary is always a testing experience for a researcher. It’s a huge opportunity to communicate cutting edge research to the public, but the way the information is presented can lack nuance and detail. This is especially true for dinosaur documentaries that are inevitably watched by young children and have to counter a huge range of myths that have built up in the popular imagination. Trying to educate, inform and entertain the audience all at once is a huge challenge.</p>
<p>Yet when I was invited to become a consultant for <a href="http://www.bbc.co.uk/programmes/b09ksl99">The real <em>T. rex</em> with Chris Packham</a>, I knew it was an opportunity not to be missed. <em>Tyrannosaurus rex</em> is not only the king of the dinosaurs but arguably the most famous animal we only know from fossils. A TV show on this species is an excellent opportunity for outreach and to try to steer conversations away from things like the endlessly recycled, and long ago settled, question of whether <em>T. rex</em> was a <a href="http://www.pnas.org/content/110/31/12560.short">predator</a> or a <a href="http://www.bioone.org/doi/abs/10.4202/app.2009.0133">scavenger</a> (the answer to this is incidentally, both).</p>
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<p>Here I must briefly mention Jurassic Park, even though I’d love not to. When the original film came out in 1993 it did more for getting across then current scientific thinking on dinosaurs than almost anything else ever could. Gone was the image of tail-dragging, upright, lumbering, swamp-dwellers and in came fast, active, and perhaps even intelligent, animals. </p>
<p>This dragged the public image of dinosaurs out of the 1960s and into the 1990s. Unfortunately, another 25 years later the science has moved on again but people’s impressions have not. The challenge is not just to introduce new ideas but overturn old ones.</p>
<h2>Latest research</h2>
<p>In the case of <em>T. rex</em> , we have learned a huge amount in the last 25 years and it has even become something of a model organism for dinosaur researchers. We have new data on their <a href="http://www.bioone.org/doi/abs/10.1666/04044.1?journalCode=pbio">movement</a>, <a href="https://peerj.com/articles/885/">feeding habits</a>, <a href="http://onlinelibrary.wiley.com/doi/10.1002/ar.20983/full">brain and inner ears</a> and more. </p>
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<p>Many of these ideas come from studying incomplete and fragmentary fossils. And however solid the research, this is never going to make exciting viewing. So ideas need to be new, easy to communicate, and contain certain level of whizz-bang for the audience. Access to specimens, and even researchers, for filming can limit the options further.</p>
<p>One excellent example of this was the programme’s section on the tyrannosaur’s bite, with an on-screen comparison with a live alligator. This gave us an opportunity to show off the gator’s bite, which was fun for the audience. But it also meant we could explain or reference the unusual shape of tyrannosaur teeth, the size and shape of their heads, the attachment sites for the jaw muscles, and the evolutionary relationship between crocodilians and dinosaurs.</p>
<h2>Bringing fossils to life</h2>
<p>We also filmed (although it was sadly cut for time from the final show) was a <em>Triceratops</em> pelvis showing <a href="http://www.tandfonline.com/doi/abs/10.1080/02724634.1996.10011297?journalCode=ujvp20">bite marks from a Tyrannosaurus</a>. This allowed us to actually include trace fossils as well. So a single short section covered multiple areas of comparative anatomy, experimental palaeontology, evolution, and ichnology (the study of animal traces like footprints). These were all integrated to build up a single coherent picture of tyrannosaur behaviour, backed by multiple research papers and presented with a bit of flair and easy frame of reference (namely a big alligator).</p>
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<p>In contrast, we had real problems getting the animal’s appearance right because the speed of research outstripped the production. We know several types of tyrannosaur had feathers and researchers have reasonably assumed that <em>T. rex</em> did too. But during production <a href="http://rsbl.royalsocietypublishing.org/content/13/6/20170092">a new paper came out</a> describing some fossilised <em>T. rex</em> skin that showed scales. Although the paper’s authors explicitly didn’t rule out feathers on <em>T. rex</em>, the research obviously meant that we needed to change our initial approach of a near fully feathered dinosaur, to one with a sparser coat.</p>
<p>Documentaries are a great way to potentially reach a huge audience and really engage with the public. The filter of writers, directors, producers and presenters means key messages can go awry, and there will always be compromises and concessions to the practicalities of filming. But the rewards are massive. Just didn’t expect anyone but your family to notice your name in the credits.</p><img src="https://counter.theconversation.com/content/89615/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Hone worked as a consultant for The Real T rex with Chris Packham, made by Talesmith Limited for the BBC.</span></em></p>A consultant on Chris Packham’s latest dinosaur show about Tyrannosaurus Rex explains how they kept it entertaining but accurate.David Hone, Senior Lecturer in Zoology, Queen Mary University of LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/562212016-03-14T19:01:35Z2016-03-14T19:01:35ZNew tyrannosaur species reveals how king of the dinosaurs won its crown<figure><img src="https://images.theconversation.com/files/114922/original/image-20160314-11288-x518v8.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Timurlengia euotica</span> <span class="attribution"><span class="source">Todd Marshall</span>, <span class="license">Author provided</span></span></figcaption></figure><p><em>Tyrannosaurus rex</em> is an icon, a dinosaur known to nearly everyone on the planet. It doesn’t get much more awesome than a 13-metre long, seven-ton superpredator that could bite through the bones of its prey. </p>
<p><em>T. rex</em> may be the <a href="https://theconversation.com/how-i-dissected-a-t-rex-it-took-chainsaws-feathers-and-lots-of-latex-42920">undisputed king</a> of the dinosaurs, but how did evolution produce such a marvellous creature, the biggest predator ever to live on land? It’s been a mystery for a long time, but a new species of tyrannosaur from Uzbekistan – a smaller and earlier cousin of <em>T. rex</em> – provides some valuable clues.</p>
<p>Meet <em>Timurlengia euotica</em>, a horse-sized tyrannosaur that lived about 90m years ago when Uzbekistan was a sweltering maze of forests and rivers bordering a vast inland sea. </p>
<h2>Small and smart</h2>
<p>The bones of <em>Timurlengia</em> were collected during a decade of field expeditions to Uzbekistan’s desolate Kyzylkum Desert, one of the driest areas of the world, led by my colleagues Alexander Averianov and Hans-Dieter Sues. They invited me to help study the fossils, and we have described the new species <a href="http://www.pnas.org/cgi/doi/10.1073/pnas.1600140113">in a paper</a> in Proceedings of the National Academy of Sciences. </p>
<p><em>Timurlengia</em> is particularly important because it is the first tyrannosaur known from the middle part of the Cretaceous period. Previously this was a dark interval of tyrannosaur history: a 20-30 million year gap in the fossil record concealing the moment when tyrannosaurs switched from fairly marginal hunters living in the underbrush to the colossal tyrants that fuel our nightmares. </p>
<p>Like pieces of a jigsaw puzzle, we have various bits of <em>Timurlengia’s</em> skeleton, including part of the snout and jaws, some teeth, various vertebrae of the neck, back and tail, and fragments of the hands and feet. These bones tell us that <em>Timurlengia</em> was about 3-4 metres long and weighed about 170-270 kilograms, roughly the size of a big horse. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/114933/original/image-20160314-11277-1ynbptj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/114933/original/image-20160314-11277-1ynbptj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=353&fit=crop&dpr=1 600w, https://images.theconversation.com/files/114933/original/image-20160314-11277-1ynbptj.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=353&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/114933/original/image-20160314-11277-1ynbptj.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=353&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/114933/original/image-20160314-11277-1ynbptj.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=443&fit=crop&dpr=1 754w, https://images.theconversation.com/files/114933/original/image-20160314-11277-1ynbptj.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=443&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/114933/original/image-20160314-11277-1ynbptj.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=443&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Fossil jigsaw.</span>
<span class="attribution"><span class="source">Todd Marshall / Stephen Brusatte</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p><em>Timurlengia</em> would have been a nasty critter, but nowhere near the brutish size of <em>T. rex</em>. In fact, it wasn’t at the top of the food chain at all. It was still living in fear of other, more primitive carnivorous dinosaurs called allosaurs, which were the apex predators of the day.</p>
<p>But there’s also another part of <em>Timurlengia’s</em> skeleton that we were able to study: the braincase, the fused bones at the back of the skull that surround the brain, ear, and sinuses. We put it into a CT scanner, which allowed us to digitally peer inside and see what the brain and sensory organs looked like. </p>
<p>This gave us quite a surprise: <em>Timurlengia</em> had the same type of brain and ear as the giant tyrannosaurs such as <em>T. rex</em>. It was very smart, and had an ear attuned to hearing low frequency sounds. Previously, these features were thought to be unique to the big tyrannosaurs, part of that toolkit of predatory superpowers that evolved as they turned into giants.</p>
<h2>Evolution story</h2>
<p>So our new Uzbek tyrannosaur helps to tell a story, about how evolution turns seemingly ordinary animals into extraordinary freaks of nature. It goes something like this.</p>
<p>Tyrannosaurs originated around 170m years ago during the Jurassic period, as human-sized, fast-running stalkers who used their long arms to grab prey. For about 80m years they stayed this way, far from spectacular, but eking out a living in the shadows. </p>
<p>Then some of these small tyrannosaurs developed sophisticated brains and senses, probably to help them better track their prey. Little did they know that, eventually, these neurosensory features would come in handy, when <a href="https://theconversation.com/six-amazing-dinosaur-discoveries-that-changed-the-world-51367">the allosaurs</a> went extinct around 80-90m years ago and a new niche at the top of the food pyramid suddenly opened up. Their intelligence and sharp senses made tyrannosaurs perfectly equipped to swoop into the top-predator role. </p>
<p>And swoop they did. Very quickly the human-to-horse-sized tyrannosaurs grew into supersized monsters, longer than a bus and weighing more than a ton. Their heads became giant killing machines and their arms, now unnecessary, shrunk down to nubbins. By 80m years ago these mega tyrannosaurs were terrorising what is now North America and Asia, spreading into all ecosystems on land, displacing smaller predators, and eating whatever they wanted.</p>
<p>It would remain this way for another 15m years or so, until the day, when <em>T. rex</em> was at the peak of its success rampaging across western North America, that a 10-kilometer-wide asteroid fell out of the sky and the world <a href="https://theconversation.com/revealed-asteroid-that-killed-the-dinosaurs-boiled-earths-atmosphere-36606">changed in an flash</a>.</p><img src="https://counter.theconversation.com/content/56221/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephen Brusatte receives funding from the European Commission (Marie Curie actions), National Science Foundation, University of Edinburgh, and American Museum of Natural History. </span></em></p>Fossils discovered in Uzbekistan help tell the story of how T. Rex evolved to become the biggest predator ever to live on land.Stephen Brusatte, Chancellor's Fellow in Vertebrate Palaeontology, The University of EdinburghLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/429202015-06-06T08:32:00Z2015-06-06T08:32:00ZHow I dissected a T.rex (it took chainsaws, feathers and lots of latex)<figure><img src="https://images.theconversation.com/files/84141/original/image-20150605-8719-1pl8ao6.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Prepare to meet thy chainsaw</span> <span class="attribution"><a class="source" href="http://channel.nationalgeographic.com/t-rex-autopsy/videos/t-rex-behind-the-build/">NatGeoTV</a></span></figcaption></figure><p>I dissected a <em>Tyrannosaurus rex</em> in front of television cameras. </p>
<p>That may be the most surreal sentence I’ve ever written. So let me explain. I’m part of a team that built a life-sized model of <em>Tyrannosaurus rex</em> and then cut it up. The spectacle is a bloody, gory two-hour television special called <em>T</em>.<em>rex</em> Autopsy. The premise may seem absurd. But this is a whole new way of communicating science to the public, and it has been one of the highlights of my career.</p>
<p>I’m a paleontologist who has been studying dinosaurs for more than a decade. I’ve dug up <em>T.rex</em> fossils in the western United States, travelled the world studying tyrannosaur bones in museums, and described some of <em>T.rex</em>’s closest cousins. It’s a pretty cool job, but it comes with something of a peculiar annoyance. Sometimes I get strange people ringing me up with their pet theories on how dinosaurs evolved from space aliens, or emailing me long screeds about how dinosaurs never existed.</p>
<p>I got an email like that last August from a television producer in London. At first it seemed like a joke: they wanted to autopsy a <em>T.rex</em> corpse in front of the cameras. Just another ambitious but insane young producer, I thought, wanting to make his mark in a television landscape where shows on Bigfoot and mermaids are now standard fare on networks that used to be dedicated to science programming.</p>
<p>But I agreed to hear him out, and very quickly my opinion changed. They wanted to dissect a <em>T.rex</em> alright, but by building the most scientifically accurate model possible, then using the pageantry of an autopsy to reveal how this most famous of dinosaurs actually functioned as a living, breathing, feeding, moving, growing animal.</p>
<p>They needed a <em>T.rex</em> expert to consult on the build of the model. I signed up immediately, along with several of my esteemed colleagues, and was later asked to expand my role and appear on-screen as one of the dissectors. That was how I found myself in the famous <a href="http://www.pinewoodgroup.com/our-studios/uk/pinewood-studios">Pinewood Studios</a> near London last April, next to where they were filming the new Bond movie, chopping up a 43-foot <em>T.rex</em> with chainsaws, dripping with synthetic blood. Not a normal day at the office for an academic scientist who spends most of his time writing grants, advising students, and lecturing. </p>
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<p>I’m incredibly proud of the end result. We’ll probably be criticised by some internet cynics who feel we’re trying to hoodwink the public into thinking this is a real tyrannosaur, or who disparage the whole idea of doing a dinosaur autopsy as too over-the-top. But that would be missing the point. </p>
<p>We took the utmost care to make sure our tyrannosaur was completely in line with what we know from fossils. Everything we couldn’t reconstruct from real fossils was informed speculation based on careful comparisons with living crocodiles, <a href="https://theconversation.com/take-a-t-rex-and-a-chicken-and-youll-see-how-dinosaurs-shrank-survived-and-evolved-into-birds-29996">which are</a> close cousins of dinosaurs, and birds, which are their descendants. And having four real scientists (a vet and three paleontologists) conducting the autopsy, without a script, made it even more authentic. </p>
<p>When I first walked into the autopsy room and saw the dinosaur, I was blown away.
Yes I had consulted on the build, but the producers had deliberately prevented me from seeing the final model so I would be surprised. It was so realistic – pretty much how I think a real <em>T.rex</em> would have looked – but made of latex, silicone, plastic, corn syrup, and various other goodies. What the artists made in four-and-a-half months and 10,000+ man hours is surely the most accurate and life-like dinosaur of all time. </p>
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<h2>Inside rex</h2>
<p>We go from head-to-tail on the dinosaur, cutting it up, talking about how each bit helps us understand <em>T.rex</em> as a living animal; what it ate, how fast it moved, what injuries it suffered, what its metabolism was like and how quickly it grew, how it reproduced. </p>
<p>So what exactly did we learn? If you thought dinosaurs were dim-witted, overgrown reptiles, think again. <em>T.rex</em> had a huge brain, its eyesight was keen, it had feathers and it grew really fast. It was essentially a huge fluffy bird from hell. </p>
<p>Some of my favourite moments were spent inside the belly of the beast, as we removed the super-sized internal organs. We don’t know much about dinosaur hearts and lungs and stomachs, because these soft parts don’t easily fossilise. But they can leave signatures on the bones, and we can use birds and crocodiles for plausible speculation. That’s how we designed the size, shape, and position of the guts in our model.</p>
<p>The organs were remarkably life-like, and I say this as somebody who has dissected a lot of animals. In particular, the suitcase-sized heart really looked and felt like it had just been cut from a real <em>T.rex</em> cadaver. The heart had four chambers inside, just like a bird, a sign of high metabolism and consistent with evidence from bones that <em>T.rex</em> was a dynamic, fast-growing animal. </p>
<figure class="align-center zoomable">
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<span class="caption">Everything was designed to be as life-like as possible.</span>
<span class="attribution"><a class="source" href="http://channel.nationalgeographic.com/t-rex-autopsy/videos/t-rex-behind-the-build/">NatGeoTV</a></span>
</figcaption>
</figure>
<p>The lungs had balloon-like extensions called air-sacs. These store air during the breathing cycle to make the lungs extra efficient, also just like birds. We know about these from the traces the air-sacs have left on <em>T.rex</em> bones. The stomach was also incredibly bird-like, with two chambers. This isn’t total speculation either: there is one spectacularly preserved tyrannosaur fossil with stomach contents that helped us in our design.</p>
<p>It’s easy to think of <em>T.rex</em> as a monster, a villain in movies, a terror in our nightmares. But it was a real living breathing animal, a great lost wonder of the world. If our programme gives people a sense of what this creature was really like, it will have been well worth the hard work. </p>
<p><em>T.rex Autopsy is on the <a href="http://channel.nationalgeographic.com">National Geographic Channel</a>.</em></p><img src="https://counter.theconversation.com/content/42920/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephen was a paid consultant and on-screen presenter for T Rex Autopsy</span></em></p>Ever wondered what it would like if you carved up the biggest land-based carnivore of all time?Stephen Brusatte, Chancellor's Fellow in Vertebrate Palaeontology, The University of EdinburghLicensed as Creative Commons – attribution, no derivatives.