Researchers discover overlooked Jurassic Park of lizards
New research published today in eLife by researchers from the Institut Català de Paleontologia Miquel Crusafont (ICP) and the University of Bristol (UB) moves back the moment of the radiation of squamates — the group of reptiles that includes lizards, snakes and worm lizards — to the Jurassic, a long time before current estimates.
The Squamata is the largest order of reptiles, including lizards, snakes and worm lizards. Squamates are all cold-blooded, and their skins are covered by horny scales. They are key parts of modern terrestrial faunas, especially in warmer climates, with an astonishing diversity of more than 10,000 species. However, understanding the evolutionary paths that forged their success are still poorly understood.
There is consensus that all the main squamate groups had arisen before the event that wiped out dinosaurs and other groups of reptiles at the end of the Mesozoic era. Before that global catastrophic event, through the Cretaceous, many terrestrial tetrapod groups like mammals, lizards and birds, apparently underwent a great diversification during the so-called Cretaceous Terrestrial Revolution, triggered by the rise of flowering plants. The scarcity of fossil remains of squamates through the Jurassic suggested that the main burst of squamate evolution happened in the Cretaceous (between 145 and 66 Myr.), when their fossil record dramatically improves.
Now, a new paper published in eLife, led by Arnau Bolet, paleontologist at the Institut Català de Paleontologia Miquel Crusafont and the University of Bristol, however, challenges this view by suggesting a much earlier radiation of squamates. Along with colleagues from the University of Bristol Michael Benton, Tom Stubbs and Jorge Herrera-Flores, their research concludes that this group of reptiles probably achieved a diverse array of adaptations in the Jurassic (between 201 and 145 Myr.), long before previously thought. “Even though Jurassic squamates are rare, reconstructed evolutionary trees show that all the main specializations of squamates evolved then, and it’s possible to distinguish adaptations of geckoes, iguanas, skinks, worm lizards, and snakes some 50 million years earlier than had been thought,” explains Michael Benton, co-author of the research.
But how could the scarce Jurassic fossils suggest an early burst in evolution? The key is in their anatomy. The few Jurassic squamates do not show primitive morphologies as would be expected, but they relate directly to the diverse modern groups. “Instead of finding a suite of generalized lizards on the stem of the squamate tree, what we found in the Jurassic were the first representatives of many modern groups, showing advanced morphological features,” says Arnau Bolet, lead author of the article.
The observed times of divergence, morphospace plots and evolutionary rates, all suggest that the Jurassic was a time of innovation in squamate evolution, during which the bases of the success of the group were established. According to these results, the apparent sudden increase in diversity observed in the Cretaceous could be related to an improved fossil record, capable of recording a larger number of species, or to a burst of origins of new species related to the new kinds of forests and insects.
Establishing the timing and mode of radiation of squamates is key for not only understanding the dynamics of terrestrial ecosystems in the Mesozoic, but also for deciphering how the group achieved an astonishing diversity of more than 10,000 species, only rivalled by birds among tetrapods.
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Pterosaur discovery solves ancient feather mystery
An international team of palaeontologists has discovered remarkable new evidence that pterosaurs, the flying relatives of dinosaurs, were able to control the colour of their feathers using melanin pigments.
The study, published in the journal Nature, was led by University College Cork (UCC) palaeontologists Dr Aude Cincotta and Prof. Maria McNamara and Dr Pascal Godefroit from the Royal Belgian Institute of Natural Sciences, with an international team of scientists from Brazil and Belgium.
The new study is based on analyses of a new 115 million year old fossilized headcrest of the pterosaur Tupandactylus imperator from north-eastern Brazil. Pterosaurs lived side by side with dinosaurs, 230 to 66 million years ago.
This species of pterosaur is famous for its bizarre huge headcrest. The team discovered that the bottom of the crest had a fuzzy rim of feathers, with short wiry hair-like feathers and fluffy branched feathers.
“We didn’t expect to see this at all,” said Dr Cincotta. “For decades palaeontologists have argued about whether pterosaurs had feathers. The feathers in our specimen close off that debate for good as they are very clearly branched all the way along their length, just like birds today.”
The team then studied the feathers with high-powered electron microscopes and found preserved melanosomes — granules of the pigment melanin. Unexpectedly, the new study shows that the melanosomes in different feather types have different shapes.
“In birds today, feather colour is strongly linked to melanosome shape.” said Prof. McNamara. “Since the pterosaur feather types had different melanosome shapes, these animals must have had the genetic machinery to control the colours of their feathers. This feature is essential for colour patterning and shows that coloration was a critical feature of even the very earliest feathers.”
Thanks to the collective efforts of the Belgian and Brazilian scientists and authorities working with a private donor, the remarkable specimen has been repatriated to Brazil. “It is so important that scientifically important fossils such as this are returned to their countries of origin and safely conserved for posterity” said Dr Godefroit. “These fossils can then be made available to scientists for further study and can inspire future generations of scientists through public exhibitions that celebrate our natural heritage.”
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T. rex’s short arms may have lowered risk of bites during feeding frenzies
Over the two decades paleontologist Kevin Padian taught a freshman seminar called The Age of Dinosaurs, one question asked frequently by undergraduates stuck with him: Why are the arms of Tyrannosaurus rex so ridiculously short?
He would usually list a range of paleontologists’ proposed hypotheses — for mating, for holding or stabbing prey, for tipping over a Triceratops — but his students, usually staring a lifesize replica in the face, remained dubious. Padian’s usual answer was, “No one knows.” But he also suspected that scholars who had proposed a solution to the conundrum came at it from the wrong perspective.
Rather than asking what the T. rex’s short arms evolved to do, Padian said, the question should be what benefit those arms were for the whole animal.
In a paper appearing in the current issue of the journal Acta Palaeontologia Polonica, Padian floats a new hypothesis: The T. rex’s arms shrank in length to prevent accidental or intentional amputation when a pack of T. rexes descended on a carcass with their massive heads and bone-crushing teeth. A 45-foot-long T. rex, for example, might have had a 5-foot-long skull, but arms only 3 feet long — the equivalent of a 6-foot human with 5-inch arms.
“What if several adult tyrannosaurs converged on a carcass? You have a bunch of massive skulls, with incredibly powerful jaws and teeth, ripping and chomping down flesh and bone right next to you. What if your friend there thinks you’re getting a little too close? They might warn you away by severing your arm,” said Padian, distinguished emeritus professor of integrative biology at the University of California, Berkeley, and a curator at the UC Museum of Paleontology (UCMP). “So, it could be a benefit to reduce the forelimbs, since you’re not using them in predation anyway.”
Severe bite wounds can cause infection, hemorrhaging, shock and eventual death, he said.
Padian noted that the predecessors of tyrannosaurids had longer arms, so there must have been a reason that they became reduced in both size and joint mobility. This would have affected not only T. rex, which lived in North America at the end of the Cretaceous period, he said, but the African and South American abelisaurids from the mid-Cretaceous and the carcharodontosaurids, which ranged across Europe and Asia in the Early and Mid-Cretaceous periods and were even bigger than T. rex.
“All of the ideas that have been put forward about this are either untested or impossible because they can’t work,” Padian said. “And none of the hypotheses explain why the arms would get smaller — the best they could do is explain why they would maintain the small size. And in every case, all of the proposed functions would have been much more effective if the arms had not been reduced.”
He admitted that any hypothesis, including his, will be hard to substantiate 66 million years after the last T. rex became extinct.
Arms and the T. rex
When the great dinosaur hunter Barnum Brown discovered the first T. rex fossils in 1900, he thought the arms were too small to be part of the skeleton. His colleague, Henry Fairfield Osborn, who described and named T. rex, hypothesized that the short arms might have been “pectoral claspers” — limbs that hold the female in place during copulation. This is analogous to some sharks and rays’ pelvic claspers, which are modified fins. But Osborn provided no evidence, and Padian noted that the T. rex’s arms are too short to go around another T. rex and certainly too weak to exert any control over a mate.
Over more than a century, other proposed explanations for the short arms included waving for mate attraction or social signaling, serving as an anchor to allow T. rex to get up from the ground, holding down prey, stabbing enemies, and even pushing over a sleeping Triceratops at night. Think cow-tipping, Padian said. And some paleontologists propose that the arms had no function at all, so we shouldn’t be concerned with them.
Padian approached the question from a different perspective, asking what benefit shorter arms might have for the animal’s survival. The answer came to him after other paleontologists unearthed evidence that some tyrannosaurids hunted in packs, not singly, as depicted in many paintings and dioramas.
“Several important quarry sites unearthed in the past 20 years preserve adult and juvenile tyrannosaurs together,” he said. “We can’t really assume that they lived together or even died together. We only know that they were buried together. But when you find several sites with the same animals, that’s a stronger signal. And the possibility, which other researchers have already raised, is that they were hunting in groups.”
Perhaps, he thought, the arms shrank to get out of the way during pack feeding. T. rex youngsters, in particular, would have been wise to wait until the larger adults were finished.
In his new paper, Padian examines speculations by other paleontologists, none of which appear to have been fully tested. The first thing he determined, by measuring the lifesize T. rex cast that dominates the atrium outside the doors of the UCMP, is that none of the hypotheses would actually work.
“The arms are simply too short,” he said. “They can’t touch each other, they can’t reach the mouth, and their mobility is so limited that they can’t stretch very far, either forward or upward. The enormous head and neck are way out in front of them and pretty much form the kind of death machine you saw in ‘Jurassic Park.'”
Twenty years ago, two paleontologists analyzed the arms and hypothesized that T. rex could have bench pressed about 400 pounds with its arms. “But the thing is, it can’t get close enough to anything to pick it up,” Padian said.
Beware of Komodo dragons
Padian’s hypothesis has analogies in some fearsome animals today. The giant Komodo Dragon lizard (Varanus komodoensis) of Indonesia hunts in groups, and when it kills prey, the larger dragons converge on the carcass and leave the remains for the smaller ones. Maulings can occur, as they do among crocodiles during feeding. The same could be true of T. rex and other tyrannosaurids, which first appeared in the Late Jurassic and reached their peak in the Late Cretaceous before becoming extinct.
Firmly establishing the hypothesis may never be possible, Padian said, but a correlation could be found if museum specimens around the world were checked for bite marks. That would be quite a feat of fossil crowdsourcing, he admitted.
“Bite wounds on the skull and other parts of the skeleton are well known in tyrannosaurs and other carnivorous dinosaurs,” he said. “If fewer bite marks were found on the reduced limbs, it could be a sign that reduction worked.”
But Padian has no illusion that his idea will be the end of the story.
“What I first wanted to do was to establish that the prevailing functional ideas simply don’t work,” he said. “That gets us back to square one. Then, we can take an integrative approach, thinking about social organization, feeding behavior and ecological factors apart from purely mechanical considerations.”
One problem in establishing the hypothesis is that there were several groups of large carnivorous dinosaurs that independently reduced their forelimbs, although in different ways.
“The sizes and proportions of the limb bones in these groups are different, but so are other aspects of their skeletons,” Padian said. “We shouldn’t expect them to be reduced in the same way. This is also true for the reduced wings of our large, living, flightless ratite birds, like the ostrich, the emu and the rhea. They evidently took different evolutionary paths for their own reasons.”
Padian sees a common thread in the history of explanations of short arms and other characteristics of T. rex.
“To me, this study of what the arms did is interesting because of how we tell stories in science and what qualifies as an explanation,” he said. “We tell a lot of stories like this about possible functions of T. rex because it’s an interesting problem. But are we really looking at the problem the right way?”
Padian’s paper is part of a Festschift honoring mammalian paleontologist Richard Cifelli, long-time head of the Oklahoma Museum of Natural History and Presidential Professor of Biology at the University of Oklahoma in Norman.
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Muscular study provides new information about how the largest dinosaurs moved and evolved
New research led by the University of Bristol has revealed how giant 50-tonne sauropod dinosaurs, like Diplodocus, evolved from much smaller ancestors, like the wolf-sized Thecodontosaurus.
In a new study published today in the journal Royal Society Open Science, researchers present a reconstruction of the limb muscles of Thecodontosaurus, detailing the anatomy of the most important muscles involved in movement.
Thecodontosaurus was a small to medium sized two-legged dinosaur that roamed around what today is the United Kingdom during the Triassic period (around 205 million years ago).
This dinosaur was one of the first ever to be discovered and named by scientists, in 1836, but it still surprises scientists with new information about how the earliest dinosaurs lived and evolved.
Antonio Ballell, PhD student in Bristol’s School of Earth Sciences and lead author of the study, said: “The University of Bristol houses a huge collection of beautifully preserved Thecodontosaurus fossils that were discovered around Bristol. The amazing thing about these fossilised bones is that many preserve the scars and rugosities that the limb musculature left on them with its attachment.”
These features are extremely valuable in scientific terms to infer the shape and direction of the limb muscles. Reconstructing muscles in extinct species requires this kind of exceptional preservation of fossils, but also a good understanding of the muscle anatomy of living, closely related species.
Antonio Ballell added: “In the case of dinosaurs, we have to look at modern crocodilians and birds, that form a group that we call archosaurs, meaning ‘ruling reptiles’. Dinosaurs are extinct members of this lineage, and due to evolutionary resemblance, we can compare the muscle anatomy in crocodiles and birds and study the scars that they leave on bones to identify and reconstruct the position of those muscles in dinosaurs.”
Professor Emily Rayfield, co-author of the study, said: “These kinds of muscular reconstructions are fundamental to understand functional aspects of the life of extinct organisms. We can use this information to simulate how these animals walked and ran with computational tools.”
From the size and orientation of its limb muscles, the authors argue that Thecodontosaurus was quite agile and probably used its forelimbs to grasp objects instead of walking.
This contrasts with its later relatives, the giant sauropods, which partly achieved these huge body sizes by shifting to a quadrupedal posture. The muscular anatomy of Thecodontosaurus seems to indicate that key features of later sauropod-line dinosaurs had already evolved in this early species.
Professor Mike Benton, another co-author, said: “From an evolutionary perspective, our study adds more pieces to the puzzle of how the locomotion and posture changed during the evolution of dinosaurs and in the line to the giant sauropods.
“How were limb muscles modified in the evolution of multi-ton quadrupeds from tiny bipeds? Reconstructing the limb muscles of Thecodontosaurus gives us new information of the early stages of that important evolutionary transition.”
This research was funded by the Natural Environment Research Council (NERC).
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Journal Reference:
- Antonio Ballell, Emily J. Rayfield, Michael J. Benton. Walking with early dinosaurs: appendicular myology of the Late Triassic sauropodomorph Thecodontosaurus antiquus. Royal Society Open Science, 2022; 9 (1) DOI: 10.1098/rsos.211356
Millipedes ‘as big as cars’ once roamed Northern England, fossil find reveals
The largest-ever fossil of a giant millipede — as big as a car — has been found on a beach in the north of England.
The fossil — the remains of a creature called Arthropleura — dates from the Carboniferous Period, about 326 million years ago, over 100 million years before the Age of Dinosaurs. The fossil reveals that Arthropleura was the largest-known invertebrate animal of all time, larger than the ancient sea scorpions that were the previous record holders.
The specimen, found on a Northumberland beach about 40 miles north of Newcastle, is made up of multiple articulated exoskeleton segments, broadly similar in form to modern millipedes. It is just the third such fossil ever found. It is also the oldest and largest: the segment is about 75 centimetres long, while the original creature is estimated to have measured around 2.7 metres long and weighed around 50 kilograms. The results are reported in the Journal of the Geological Society.
The fossil was discovered in January 2018 in a large block of sandstone that had fallen from a cliff to the beach at Howick Bay in Northumberland. “It was a complete fluke of a discovery,” said Dr Neil Davies from Cambridge’s Department of Earth Sciences, the paper’s lead author. “The way the boulder had fallen, it had cracked open and perfectly exposed the fossil, which one of our former PhD students happened to spot when walking by.”
Unlike the cool and wet weather associated with the region today, Northumberland had a more tropical climate in the Carboniferous Period, when Great Britain lay near the Equator. Invertebrates and early amphibians lived off the scattered vegetation around a series of creeks and rivers. The specimen identified by the researchers was found in a fossilised river channel: it was likely a moulted segment of the Arthropleura’s exoskeleton that filled with sand, preserving it for hundreds of millions of years.
The fossil was extracted in May 2018 with permission from Natural England and the landowners, the Howick Estate. “It was an incredibly exciting find, but the fossil is so large it took four of us to carry it up the cliff face,” said Davies.
The fossil was brought back to Cambridge so that it could be examined in detail. It was compared with all previous records and revealed new information about the animal’s habitat and evolution. The animal can be seen to have only existed in places that were once located at the Equator, such as Great Britain during the Carboniferous. Previous reconstructions have suggested that the animal lived in coal swamps, but this specimen showed Arthropleura preferred open woodland habitats near the coast.
There are only two other known Arthropleura fossils, both from Germany, and both much smaller than the new specimen. Although this is the largest Arthropleura fossil skeleton ever found, there is still much to learn about these creatures. “Finding these giant millipede fossils is rare, because once they died, their bodies tend to disarticulate, so it’s likely that the fossil is a moulted carapace that the animal shed as it grew,” said Davies. “We have not yet found a fossilised head, so it’s difficult to know everything about them.”
The great size of Arthropleura has previously been attributed to a peak in atmospheric oxygen during the late Carboniferous and Permian periods, but because the new fossil comes from rocks deposited before this peak, it shows that oxygen cannot be the only explanation.
The researchers believe that to get to such a large size, Arthropleura must have had a high-nutrient diet. “While we can’t know for sure what they ate, there were plenty of nutritious nuts and seeds available in the leaf litter at the time, and they may even have been predators that fed off other invertebrates and even small vertebrates such as amphibians,” said Davies.
Arthropleura animals crawled around Earth’s equatorial region for around 45 million years, before going extinct during the Permian period. The cause of their extinction is uncertain, but could be due to global warming that made the climate too dry for them to survive, or to the rise of reptiles, who out-competed them for food and soon dominated the same habitats.
The fossil will go on public display at Cambridge’s Sedgwick Museum in the New Year.
Neil Davies is a Fellow of Churchill College, Cambridge. The research was supported in part by the Natural Environment Research Council.
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An ancient relative of Velociraptor is unearthed in Great Britain
A new bird-like dinosaur that used brute strength to overcome its prey has been found by paleontologists combing through fossils found on the Isle of Wight, on the South Coast of Great Britain.
The new animal has been named Vectiraptor greeni after local collector Mick Green who discovered its bones after they became washed from the rocks on the island’s south coast. It was an older, more heavily built, relative of the predator Velociraptor. The fearsome animal was about the size of a wolf, about 3 metres (10 feet) long, from nose to tail, and would have used huge slashing talons on its feet to dispatch its prey. Its finely serrated teeth were then used to bite off pieces of the kill.
The dinosaur would have prowled through the forests that covered the land in the Early Cretaceous, 125 million years ago. It died and lay buried until 2004, when storms and waves eroded away the rocks that had kept its bones hidden. Yet another 20 years passed before scientists from the Universities of Bath and Portsmouth studied the fossils and made the surprising find that the bones represented a new species. Their discovery is described this week in the journal Cretaceous Research.
Vectiraptor belonged to a group of dinosaurs called dromaeosaurs, or raptors. These bird-like dinosaurs were specialist hunters and, like their modern-day avian relatives, were covered in long feathers. Their jaws were full of blade-like, serrated teeth and they had huge scythe-shaped claws on their feet, used to slash at their prey, causing it to rapidly bleed to death.
Well-known members of the raptors include Velociraptor from Mongolia, and Deinonychus, and the giant Utahraptor from the United States. A smaller raptor has previously been described from the Isle of Wight but Vectiraptor marks the first time a large raptor has been found in England. Although only fragments of the skeleton have survived- a pair of vertebrae from the back, and part of the hips — what is known suggests a large, powerfully built animal.
“This was a large, and very heavily constructed animal,” said Dr Nick Longrich, who led the study from the Milner Centre for Evolution at the University of Bath. “The bones are thick-walled and massive. It clearly didn’t hunt small prey, but animals as large or larger than itself.”
Although not the biggest predator in its environment — top predators included the allosaur Neovenator, spinosaurs like Baryonyx, and an early tyrannosaur called Eotyrannus — Vectiraptor would have been a threat both to smaller dinosaurs and juveniles of large dinosaurs. With strong arms and talons, it may have climbed trees like modern leopards. The heavy bones suggest an animal that relied less on speed and more on strength, and perhaps ambushes, to tackle its prey.
“It’s a tantalising hint at the diversity of dinosaurs in England at this time,” said Dr Longrich.
This is the first time a large raptor has been found in the UK. “There’s an extraordinary diversity of dinosaurs known in England in the Cretaceous, and even after more than a century of study, we continue to find new species,” said Dr Longrich. “Although palaeontologists have been studying these dinosaurs for a long time, it’s hard going. We have to wait for the sea cliffs to fall and expose bits of bone, or for the waves to wash them out of the rocks. We’ve spent two centuries on the Isle of Wight piecing together our picture of English dinosaurs.”
Co-author Professor Dave Martill of the University of Portsmouth notes that raptors closely related to Velociraptor have also been found in Mongolia, suggesting that England may have lain along an important dispersal route for dinosaurs. Professor Martill said, given the similarity between North American and Mongolian dinosaur faunas in the Early Cretaceous, it was only a matter of time before someone discovered a raptor dinosaur in England.
A remarkable number of dinosaur species originate from this small island off southern England. Ancient England was something of a crossroads for dinosaurs. At the time the continents were closer together, with some connected by land bridges. Dinosaurs likely wandered in from North America and Asia, or perhaps swam from Africa. Europe was a sort of crossroads linking the continents.
A chance encounter
Vectiraptor greeni was named after amateur paleontologist Mick Green, who discovered the remains in in 2004 but didn’t appreciate the importance of his find until he was forced by ill-health to stop collecting fossils in 2012. He then turned his attention to prising the dinosaur bones free from the hard ironstone surrounding them.
One day, chatting over a beer, he showed the fossils to Isle of Wight palaeontologist Megan Jacobs and Dr Longrich who puzzled over them, and at first struggled to make sense of them, until they noticed tell-tale similarities to other raptors. Mr Green allowed the bones to be studied, and they turned out to represent a new genus and species. The bones have now been donated to the Dinosaur Isle Museum at Sandown on the Isle of Wight.
“This dinosaur is incredibly exciting, adding to the huge diversity of dinosaurs here on the Isle of Wight, and helping to build a bigger picture of the Early Cretaceous world,” said Megan Jacobs, a collaborator on the project. “This little dinosaur also serves as an excellent example of the importance of amateur fossil collectors, and how working with them can produce important scientific research, which would otherwise not be possible.”
Without the dedication of Mick Green and others on the island, she noted, this dinosaur would have been lost to the sea.
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Sauropod dinosaurs were restricted to warmer regions of Earth
Giant, long-necked sauropods, thought to include the largest land animals ever to have existed, preferred to live in warmer, more tropical regions on Earth, suggesting they may have had a different physiology from other dinosaurs, according to a new study
Giant, long-necked sauropods, thought to include the largest land animals ever to have existed, preferred to live in warmer, more tropical regions on Earth, suggesting they may have had a different physiology from other dinosaurs, according to a new study led by researchers at UCL and the University of Vigo.
The study, published in the journal Current Biology, investigated the enigma of why sauropod fossils are only found at lower latitudes, while fossils of other main dinosaur types seem ubiquitously present, with many located in the polar regions.
The researchers analysed the fossil record across the Mesozoic era (the time of the dinosaurs), lasting from around 230 to 66 million years ago, looking at occurrences of fossils of the three main dinosaur types: sauropods, which include the Brontosaurus and the Diplodocus, theropods (“lizard-hipped”), which include velociraptors and Tyrannosaurus rex, and ornithischians (“bird-hipped”) such as the Triceratops.
Combining this fossil data with data about climate throughout the period, along with information about how continents have moved across the globe, the researchers concluded that sauropods were restricted to warmer, drier habitats than other dinosaurs. These habitats were likely to be open, semi-arid landscapes, similar to today’s savannahs.
Co-author Dr Philip Mannion (UCL Earth Sciences) said: “Our research shows that some parts of the planet always seemed to be too cold for sauropods. They seem to have avoided any temperatures approaching freezing. Other dinosaur types, in contrast, could thrive in Earth’s polar regions, from innermost Antarctica to polar Alaska — which, due to the warmer climate, were ice-free, with lush vegetation.
“This suggests sauropods had different thermal requirements from other dinosaurs, relying more on their external environment to heat their bodies — slightly closer to being ‘cold-blooded’, like modern-day reptiles. Their grand size hints that this physiology may have been unique.”
First author Dr Alfio Alessandro Chiarenza, formerly of UCL who is now based at the University of Vigo, Spain, said: “It may be that sauropods were physiologically incapable of thriving in colder regions, or that they thrived less well in these areas than their dinosaurian cousins and were outcompeted.
“A mix of features may have helped sauropods shed heat more easily than mammals do today. Their long necks and tails would have given them a larger surface area, and they may have had a respiratory system more akin to birds, which is much more efficient.
“Some species of theropods and ornithischians are known to have had feathers or downy fur helping them retain body warmth. This suggests they may have generated their own body heat. For sauropods, however, there is no evidence of this kind of insulation.
“Sauropods’ strategies for keeping their eggs warm may also have differed from the other dinosaurs. Theropods probably warmed eggs by sitting on them, whereas ornithischians seem to have used heat generated by decaying plants. Sauropods, meanwhile, may have buried their eggs, relying on heat from the sun and the ground.”
In their paper, the researchers noted that the fossil record showed zero occurrences of sauropods above a latitude of 50 degrees north — an area encompassing most of Canada, Russia, northern Europe and the UK — or below 65 degrees south, encompassing Antarctica. In contrast, there are rich records for theropods and ornithischians living above 50 degrees north in later periods (from 145 million years ago).
To test if this was a true reflection of where sauropods lived, researchers used a statistical technique to adjust for gaps in the fossil record, and also analysed where the highest diversities of dinosaur types were in different periods throughout the Mesozoic era.
They combined fossil data with climate data, allowing an estimate of the temperature ranges of the dinosaur types’ habitats, finding that sauropods’ range across the latitudes was more restricted during colder periods.
They then used habitat modelling to infer which regions of the globe would likely be suitable for sauropods and the other dinosaur types to live.
While in the past it was believed that dinosaurs were ectothermic (“cold-blooded”), like reptiles today, relying on the external environment to heat their bodies, it is now thought they were closer to “warm-blooded” mammals, generating some of their own body heat (endothermic).
The study authors said sauropods may have had a unique in-between physiology, closer to being cold-blooded than other dinosaur types.
The study involved researchers from UCL, the University of Vigo, the University of Bristol, and the Natural Museum of Natural History, Smithsonian Institution, Washington, USA, and received funding from the European Research Council and the Royal Society.
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Big-headed ancient fish had land on its mind
New insights into emergence of tetrapods
Sophisticated CT scanning of the cranium of an Australian fish fossil has given new insights to explain how fish first left the water to invade land about 370 million years ago.
Supported by the Australian Research Council and international experts, the new research led by Flinders University palaeontologists studied Cladarosymblema narrienense, a 330 million-year-old fish from the Carboniferous Period found in Queensland, which is an ancestor of the first land animals or four-limbed vertebrate tetrapods.
Cladarosymblema is a type of ‘megalichthyid’ fish, a group which existed from the Devonian-to-Permian periods, typically living in freshwater environments, and they were large, predatory animals. Through scanning the fossil, they found evidence this fish had a brain similar to its eventual terrestrial descendants, compared to the brains of other fishes which remained living in water.
“This fish from Queensland is one of the best preserved of its kind in the entire world, in perfect 3D shape, which is why we chose to work on it,” says Professor John Long, Strategic Professor in Palaeontology at Flinders University.
While this fish was first described in 1995, by Professor Long and others who had earlier explored and excavated the Queensland fossil site, parts of its anatomy have remained unknown — although using Australia’s largest cabinet CT scanner, located at Flinders University’s Tonsley campus, as well as the Australian Synchrotron in Melbourne, has allowed researchers to unlock new data from this fossil.
New information obtained from often unseen internal bones has been revealed in these scans — particularly in the gill arch skeleton, the shoulder girdle and the palate bones (the upper mouth roof area).
“This helps us to understand the functional morphology and relationships of Cladarosymblema,” says Dr Alice Clement, lead author of the new paper and part of the Flinders Palaeontology Group.
“Additionally, a cranial endocast (mould of the internal cavity of this fish’s unusually large skull) gives clues as to the shape of the brain of this animal. The area for the pituitary gland (so-called the ‘master gland’) is relatively large, suggesting a significant role in regulating various important endocrine glands.”
3D imagery here: https://youtu.be/zSs1b74Pk1s
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Ammonite muscles revealed in 3D from Jurassic fossil
They found that the now-extinct molluscs sported hyponomes: tube-like syphons through which water is expelled to jet propel animals forward in water, as found in modern squid and octopuses. They also found strong muscles that ammonites used to retract into their shells to defend against predators.
The team, including researchers from Cardiff University and Imperial College London, found this by analysing the muscles and organs of an exceptionally well-preserved ammonite fossil found over 20 years ago in Gloucestershire, UK.
The research, published today in Geology, marks the first time an ammonite’s softer parts have been visualised in three dimensions — and is thanks to a combination of modern technology, the fossil’s exceptional preservation, and collaboration across interdisciplinary teams and facilities.
The findings add insight into how ammonites lived and provide evidence that coleoids, the sub-group of animals containing squid, octopuses, and cuttlefish, might be evolutionarily closer to ammonites than previously thought.
Study co-author Dr Alan Spencer, from Imperial’s Department of Earth Science and Engineering and the Natural History Museum, said: “This ammonite is remarkably well preserved, which is very rare. New imaging techniques allowed us to visualise the internal soft parts of ammonites that have so far resisted all our previous efforts to describe them. This is a major breakthrough in ammonite palaeobiology.”
Squid-like propulsion
Ammonites, which became extinct around 66 million years ago, once thrived in oceans as dinosaurs ruled the Earth. They are among the most common fossils worldwide, but almost everything we know about them so far is based on their hard shells as these are more easily preserved over millennia than bodily tissues. Thus, ammonite fossils with preserved muscles and organs are extremely rare.
To carry out the study, the researchers studied the five-centimetres-across ammonite fossil which was found within an exposed Jurassic sediment at a Gloucestershire site in 1998. They looked at the fossil’s remaining soft tissues and scarring where muscles once attached to the inside of its shell.
By combining high-resolution X-ray and high-contrast neutron imaging, they created a detailed 3D computer reconstruction of the structure, size and orientation of its muscles and organs. From this detailed model, they were able to infer the functions of the muscles and organs.
The arrangement and relative strength of the muscles suggests ammonites swam by expelling water through their hyponomes, found next to the opening to the body chamber. This type of swimming, called jet propulsion, is used by a wide range of living animals, including cephalopods — the larger group to which ammonites belong.
The imaging also revealed paired muscles extending from the ammonite’s body, likely used to retract the animal deep into the body chamber for protection. This would have been an important anti-predator adaptation in ammonites, which lacked defensive features like the ink sac seen in modern relatives like octopuses, squid, and cuttlefish.
Patience yields results
Because ammonites’ soft tissues are rarely preserved, scientists have used modern Nautilus as a ‘body-plan’ for reconstructing ammonite biology. However, this study highlights that ammonites and Nautilus may not be as similar as previously thought.
The study’s lead author Dr Lesley Cherns of Cardiff University said: “Preservation of soft parts is exceptionally rare in ammonites, even in comparison to fossils of closely related animals like squid. We found evidence for muscles that are not present in Nautilus, which provided important new insights into the anatomy and functional morphology of ammonites.”
The findings demonstrate that combining different imaging techniques can be highly effective for investigating fossil soft tissues, highlighting exciting possibilities for studying the internal structure of well-preserved specimens.
Dr Spencer added: “Despite being discovered over 20 years ago, scientists have resisted the destructive option of cutting it apart to see what’s inside. Although this would have been much quicker, it risked permanent loss of some information. Instead, we waited until non-destructive technology caught up — as it now has! This allowed us to understand these interior structures without causing this unique and rare fossil any damage.
“This result is a testament to both the patience shown and the amazing ongoing technological advances in palaeontology.”
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Materials provided by Imperial College London. Original written by Nicky Jenner, Caroline Brogan. Note: Content may be edited for style and length.
Journal Reference:
- Lesley Cherns, Alan R.T. Spencer, Imran A. Rahman, Russell J. Garwood, Christopher Reedman, Genoveva Burca, Martin J. Turner, Neville T.J. Hollingworth, Jason Hilton. Correlative tomography of an exceptionally preserved Jurassic ammonite implies hyponome-propelled swimming. Geology, 2021; DOI: 10.1130/G49551.1
Fleshing out the bones of Quetzalcoatlus, Earth’s largest flier ever
70 million-year-old fossils reveal unique walking behavior of this huge, heron-like pterosaur
Look around any wetland today and you’re likely to see 3-foot-tall egrets or 4-foot-tall herons wading in the shallows in stealthy search of fish, insects or crustaceans.
But 70 million years ago, along the Rio Grande River in Texas, a more impressive and scarier creature stalked the marshes: the 12-foot-tall pterosaur known as Quetzalcoatlus. With a 37- to 40-foot wingspan, it was the largest flying animal that ever lived on Earth.
In six papers published this week as a Memoir by the Society of Vertebrate Paleontology, scientists and an artist provide the most complete picture yet of this dinosaur relative, the largest example of which is represented by just a single set of fossilized bones collected in the late 1970s from Big Bend National Park. The papers describe the pterosaur’s geological and ecological setting during the Upper Cretaceous, its anatomy and taxonomic position, and how it moved on the ground and in the air.
One of the papers, co-authored by University of California, Berkeley, paleontologist Kevin Padian, emeritus professor of integrative biology and emeritus curator in the UC Museum of Paleontology, answers some of the mysteries surrounding the flying and walking behavior of this unique animal, about which little has been published since its discovery more than 45 years ago. How can an animal walk with wings so long that they touch the ground when folded? What did it eat, and how did it feed? How strong a flier was it? And how does an animal whose wings span 40 feet, yet whose legs are only 6 feet high at the hip, launch itself into the air?
“This ancient flying reptile is legendary, although most of the public conception of the animal is artistic, not scientific,” said Padian, who co-edited the monograph. “This is the first real look at the entirety of the largest animal ever to fly, as far as we know. The results are revolutionary for the study of pterosaurs — the first animals, after insects, ever to evolve powered flight.”
The original Quetzalcoatlus fossils were discovered by Douglas Lawson, who at the time was a 22-year-old studying for a master’s degree in geology at the University of Texas, Austin, and later became a doctoral student at UC Berkeley. The fossil pterosaur — which he named after the Aztec flying serpent god — consisted of a partial wing that implied a size comparable to that of some airplanes and was at least 50% bigger than the wings of the largest known bird, an extinct and much larger relative of living condors and a descendent of the dinosaurs.
Unlike the serpent god, Quetzalcoatlus had no feathers: Its body, including wings of skin and fibers of keratin, was covered with hair, as in all pterosaurs. Like dinosaurs, it was likely warm- blooded and active. It had lost its tail, presumably to improve its maneuverability, and its 6-foot neck and 4-foot crested skull suggest a stork on steroids.
Wann Langston, for many years a curator of UT Austin’s Vertebrate Paleontology Laboratory, invited many colleagues, including Padian, to work on the fossils, but was unable to publish a full description of the animal before his death in 2013.
At the request of the laboratory, Padian teamed up with engineer and amateur paleontologist James Cunningham and London artist John Conway — all longtime colleagues of Langston — to look at the fossilized bones of Lawson’s find, Quetzalcoatlus northropi, and compare them with more numerous specimens of a smaller Quetzalcoatlus species in order to better understand feeding, flying, walking and launch behavior. Langston is listed as a fourth co-author of the paper.
“Jim and John and I came to the project with very different ideas,” Padian said, “but we didn’t put a single statement in our paper unless all three of us agreed on it.”
Playing with the bones
To understand how the Quetzalcoatlus pterosaurs behaved, Padian and colleagues manipulated casts of bones from about a dozen smaller and more complete pterosaur fossil skeletons, including those of the species Quetzalcoatlus lawsoni, which is newly-named after Lawson in one of the accompanying papers. The Q. lawsoni fossils were found in the same Javelina Formation in West Texas around the time the larger Q. northropi was excavated. The smaller specimens are half the size of the larger one Lawson initially found, but they consist of about 300 fossilized bone bits. The larger animal, however, is known only from a few wing bones: a humerus and an ulna from the upper arm and forearm, respectively.
The picture that Padian, Cunningham and Conway paint is of an animal similar to egrets and herons in how it feeds and launches itself into the air, like condors and vultures in how it soars, but, because of its enormous wings, unlike any other known animal in how it walks.
“Pterosaurs have huge breastbones, which is where the flight muscles attach, so there is no doubt that they were terrific fliers,” he said. “Their upper arm bone — the humerus — has huge, bony crests for anchoring the flight muscles, which are larger than those of birds and far larger than those of bats. The wings worked essentially like those of birds and other dinosaurs, to which pterosaurs are most closely related. Despite two centuries of reconstructing pterosaurs like bats, there is no evidence for this view: Bats are unique and very different from birds and pterosaurs.”
Like birds and bats and even humans, the forelimbs of pterosaurs have three segments: the upper arm or humerus, from the shoulder socket to the elbow; the forearm, including the radius and ulna; and the wrist and hand bones. But unlike birds and bats, the leading edge of the outer part of the pterosaur wing is formed by a giant wing-finger.
“It’s like having a ski pole extended from the base of your fingers and angled 90 degrees outward,” Padian said.
Quetzalcoatlus was bipedal, that is, it walked on two legs. But because its forelimb bones are so elongated, its wings could not avoid touching the ground when folded. This four-point stance suggested to some that the pterosaurs walked like a vampire bat, which uses its forelimbs to propel itself forward on the ground. But study of the bones shows that the pterosaur could not have used the wings for propulsion. When grounded, they could only move their wings forward or to the side.
“Once you put the forelimbs on the ground in these pterodactyls, you can’t rotate the forelimb back to push the animal forward like any sensible quadruped because there’s a bone in the way in the shoulder,” Padian said.
That doesn’t mean they were clumsy.
“To avoid tripping, the animal first raised its left arm, then advanced its left leg in a full step, then it placed the hand on the ground,” he said. “The process was repeated with the right limb: The right arm lifted, the right leg advanced and emplaced the right foot, and then the right hand descended. It seems a cumbersome process to us, but the animal could execute the gait quickly and easily.”
This fits perfectly with trackways of walking pterosaurs discovered in Southern France in the 1990s, Padian said.
Powerful legs provide a jump-start
However, because its legs were shorter than its wings, taking off was not as simple as flapping to generate lift.
“There are problems with a running takeoff. In the smaller specimens, you’re looking at a 9-foot wing that’s probably flexed to a bit under 8 feet on each side. The hip is maybe 3 to 4 feet above the ground. So, if you’re running along, you can only depress the wings about 40 degrees below the horizontal before they hit the ground. Ideally, you’d like to get a deeper stroke, and because these wings are so large, you can’t move them very quickly, so a faster stroke won’t work. Running helps you with takeoff speed, but that isn’t the problem.”
Instead, pterosaurs likely used their strong rear legs to jump upward, and then, once the ground clearance equaled the wing length, began to flap. Herons and egrets do the same, though they are considerably smaller than Quetzalcoatlus.
“If they could jump twice their hip height, to 8 feet, the wings would be able to clear the ground, and they could execute a deeper flight stroke,” Padian said. “This may be the best option for taking off, though it depends on sufficient power from the legs.”
He said that the forelimbs might have helped push the creature off the ground in the manner of vampire bats, but this would have required extraordinary strength of the extensor muscles of the forearm, which seems unlikely.
Given its habitat — inland marshes and open fields, much different from the West Texas desert today — the pterosaur’s most likely feeding strategy would resemble that of today’s egrets and herons, which are waders and stalkers with a varied diet. They sift the mud for crabs, worms and clams, but also snatch up small fish, insects, snakes and lizards.
“Some people said it was a carrion feeder, some people said it flew over the water and plucked fish like a pelican. Those things don’t work,” he said. “The jaws are very long and thin, tapering to a point. Wann used to call them chopsticks. And if you look at a heron or egret’s jaws, they’re the same — good for plucking lizards and other small game, but definitely not carcass-scavenging. It had no teeth.”
Quetzalcoatlus could have been as skilled at stalking prey from the air as from land.
“This animal could raise its head and neck vertically, so as to swallow the small prey it seized with its jaws. It could lower the great head far below the horizontal, so if it were cruising above dry land, it might have been able to swoop down and pluck an unsuspecting animal,” Padian said. “Walking about on land, it could move its head and neck to an arc of 180 degrees, capable of full vision all around it.”
Nearly 40 years ago, Padian teamed up with paleontologist Jean-Michel Mazin, who had discovered the pterosaur trackways in France, to describe the landing techniques of pterosaurs.
“The animal had to flap its wings to stall and slow its descent. And then it lands with its back feet and takes a little hop,” Padian said. “And then it puts down its front feet, then it assumes a four-legged posture, straightens itself out and walks away.”
The team’s detailed reconstruction of the anatomy and behavior of Quetzalcoatlus was possible thanks to the excellent condition of the fossils, which were preserved in nearly their original three-dimensional shape, he said. This is rare for fossil animals and especially for pterosaurs, which have extremely thin bones that are usually crushed.
Padian admits that questions about Quetzalcoatlus and pterosaurs, in general, still remain, such as the shape of the wing membranes and where they were attached to the body. He pointed out that the legs were organized like those of birds and other dinosaurs, with the knees pointed forward, and that they put one foot in front of the other when walking. They could not have angled the legs sideways, however, like bats, which have unique hip joints that permit this.
Because of this, pterosaur legs would have been useless for extending the wings, which suggests that the wings were attached to the body only. Pterosaurs likely resembled birds in flight, with their legs tucked underneath.
All of the details will be online for the world to read and critique, thanks to Nathan Myhrvold, former chief technology officer of Microsoft Corp., who funded the various teams to prepare the monographs and paid for open access. The monograph was coedited by Matthew Brown, director of UT Austin’s Vertebrate Paleontology Collections at the Jackson School of Geosciences.
“It’s really exciting to get together all these people who have been involved with studying (Quetzalcoatlus) over the years, all these different aspects, from the history of discovery to the ancient environment of the animal to the study of what its anatomy was like and how many kinds of critters there were and how it walked and flew and took off, and so on,” Padian said. “To put all these things in a single set of papers in a monograph is kind of one-stop-shopping for this animal. And we’re really delighted to be able to make it open access, thanks to Nathan.”
Supplement on The Late Cretaceous pterosaur Quetzalcoatlus Lawson: https://www.tandfonline.com/toc/ujvp20/41/sup1
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Materials provided by University of California – Berkeley. Original written by Robert Sanders. Note: Content may be edited for style and length.
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