paleontology

Wyoming dinosaur mummies give us a new view of duck-billed species

Biology, dinosaurs, duck-billed dinosaurs, fossils, paleontology, Science / 9u50fv / November 15, 2025

Exquisitely preserved fossils come from a single site in Wyoming.

The scaly skin of a crest over the back of the juvenile duck-billed dinosaur Edmontosaurus annectens. Credit: Tyler Keillor/Fossil Lab

Edmontosaurus annectens, a large herbivore duck-billed dinosaur that lived toward the end of the Cretaceous period, was discovered back in 1908 in east-central Wyoming by C.H. Sternberg, a fossil collector. The skeleton, later housed at the American Museum of Natural History in New York and nicknamed the “AMNH mummy,” was covered by scaly skin imprinted in the surrounding sediment that gave us the first approximate idea of what the animal looked like.

More than a century later, a team of paleontologists led by Paul C. Sereno, a professor of organismal biology at the University of Chicago, got back to the same exact place where Sternberg dug up the first Edmontosaurus specimen. The researchers found two more Edmontosaurus mummies with all fleshy external anatomy imprinted in a sub-millimeter layer of clay. For the first time, we uncovered an accurate image of what Edmontosaurus really looked like, down to the tiniest details, like the size of its scales and the arrangement of spikes on its tail. And we were in for at least a few surprises.

Evolving images

Our view of Edmontosaurus changed over time, even before Sereno’s study. The initial drawing of Edmontosaurus was made in 1909 by Charles R. Knight, a famous paleoartist, who based his visualization on the first specimen found by Sternberg. “He was accurate in some ways, but he made a mistake in that he drew the crest extending throughout the entire length of the body,” Sereno says. The mummy Knight based his drawing on had no tail, so understandably, the artist used his imagination to fill in the gaps and made the Edmontosaurus look a little bit like a dragon.

An update to Knight’s image came in 1984 due to Jack Horner, one of the most influential American paleontologists, who found a section of Edmontosaurus tail that had spikes instead of a crest. “The specimen was not prepared very accurately, so he thought the spikes were rectangular and didn’t touch each other,” Sereno explains. “In his reconstruction he extended the spikes from the tail all the way to the head—which was wrong,” Sereno says. Over time, we ended up with many different, competing visions of Edmontosaurus. “But I think now we finally nailed down the way it truly looked,” Sereno claims.

To nail it down, Sereno’s team retraced the route to where Sternberg found the first Edmontosaurus mummy. This was not easy, because the team had to rely on Sternberg’s notes, which often referred to towns and villages that were no longer on the map. But based on interviews with Wyoming farmers, Sereno managed to reach the “mummy zone,” an area less than 10 kilometers in diameter, surprisingly abundant in Cretaceous fossils.

“To find dinosaurs, you need to understand geology,” Sereno says. And in the “mummy zone,” geological processes created something really special.

Dinosaur templating

The fossils are found in part of the Lance Formation, a geological formation that originated in the last three or so million years of the Cretaceous period, just before the dinosaurs’ extinction. It extends through North Dakota, South Dakota, Wyoming, Montana, and even to parts of Canada. “The formation is roughly 200 meters thick. But when you approach the mummy zone—surprise! The formation suddenly goes up to a thousand meters thick,” Sereno says. “The sedimentation rate in there was very high for some reason.”

Sereno thinks the most likely reason behind the high sedimentation rate was frequent and regular flooding of the area by a nearby river. These floods often drowned the unfortunate dinosaurs that roamed there and covered their bodies with mud and clay that congealed against a biofilm which formed at the surface of decaying carcasses. “It’s called clay templating, where the clay sticks to the outside of the skin and preserves a very thin layer, a mask, showing how the animal looked like,” Sereno says.

Clay templating is a process well-known by scientists studying deep-sea invertebrate organisms because that’s the only way they can be preserved. “It’s just no one ever thought it could happen to a large dinosaur buried in a river,” Sereno says. But it’s the best explanation for the Wyoming mummy zone, where Sereno’s team managed to retrieve two more Edmontosaurus skeletons surrounded by clay masks under 1 millimeter thick. These revealed the animal’s appearance with amazing, life-like accuracy.

As a result, the Edmontosaurus image got updated one more time. And some of the updates were rather striking.

Delicate elephants

Sereno’s team analyzed the newly discovered Edmontosaurus mummies with a barrage of modern imaging techniques like CT scans, X-rays, photogrammetry, and more. “We created a detailed model of the skin and wrapped it around the skeleton—some of these technologies were not even available 10 years ago,” Sereno says. The result was an updated Edmontosaurus image that includes changes to the crest, the spikes, and the appearance of its skin. Perhaps most surprisingly, it adds hooves to its legs.

It turned out both Knight and Horner were partially right about the look of Edmontosaurus’ back. The fleshy crest, as depicted by Knight, indeed started at the top of the head and extended rearward along the spine. The difference was that there was a point where this crest changed into a row of spikes, as depicted in the Horner version. The spikes were similar to the ones found on modern chameleons, where each spike corresponds one-to-one with the vertebrae underneath it.

“Another thing that was stunning in Edmontosaurus was the small size of its scales,” Sereno says. Most of the scales were just 1 to 4 millimeters across. They grew slightly larger toward the bottom of the tail, but even there they did not exceed 1 centimeter. “You can find such scales on a lizard, and we’re talking about an animal the size of an elephant,” Sereno adds. The skin covered with these super-tiny scales was also incredibly thin, which the team deduced from the wrinkles they found in their imagery.

And then came the hooves. “In a hoof, the nail goes around the toe and wraps, wedge-shaped, around its bottom,” Sereno explains. The Edmontosaurus had singular, central hooves on its fore legs with a “frog,” a triangular, rubbery structure at the underside. “They looked very much like equine hooves, so apparently these were not invented by mammals,” Sereno says. “Dinosaurs had them.” The hind legs that supported most of the animal’s weight, on the other hand, had three wedge-shaped hooves wrapped around three digits and a fleshy heel toward the back—a structure found in modern-day rhinos.

“There are so many amazing ‘firsts’ preserved in these duck-billed mummies,” Sereno says. “The earliest hooves were documented in a land vertebrate, the first confirmed hooved reptile, and the first hooved four-legged animal with different forelimb and hindlimb posture.” But Edmontosaurus, while first in many aspects, was not the last species Sereno’s team found in the mummy zone.

Looking for wild things

“When I was walking through the grass in the mummy zone for the first time, the first hill I found a T. rex in a concretion. Another mummy we found was a Triceratops,” Sereno says. Both these mummies are currently being examined and will be covered in the upcoming papers published by Sereno’s team. And both are unique in their own way.

The T. rex mummy was preserved in a surprisingly life-like pose, which Sereno thinks indicates the predator might have been buried alive. Edmontosaurus mummies, on the other hand, were positioned in a death pose, which meant the animals most likely died up to a week before the mud covered their carcasses. This, in principle, should make the T. rex clay mask even more true-to-life, since there should be no need to account for desiccation and decay when reconstructing the animal’s image.

Sereno, though, seems to be even more excited about the Triceratops mummy. “We already found Triceratops scales were 10 times larger than the largest scales on the Edmontosaurus, and its skin had no wrinkles, so it was significantly thicker. And we’re talking about animals of similar size living in the same area and in the same time,” Sereno says. To him, this could indicate that the physiology of the Triceratops and Edmontosaurus was radically different.

“We are in the age of discovery. There are so many things to come. It’s just the beginning,” Sereno says. “Anyway, the next two mummies we want to cover are the Triceratops and the T. Rex. And I can already tell you what we have with the Triceratops is wild,” he adds.

Science, 2025. DOI: 10.1126/science.adw3536

Jacek Krywko is a freelance science and technology writer who covers space exploration, artificial intelligence research, computer science, and all sorts of engineering wizardry.

Wyoming dinosaur mummies give us a new view of duck-billed species Read More »

World’s oldest RNA extracted from ice age woolly mammoth

ancient DNA, ancient RNA, Biology, evolution, Genomics, mammoths, paleontology, Science / Beth Washington / November 14, 2025

A young woolly mammoth now known as Yuka was frozen in the Siberian permafrost for about 40,000 years before it was discovered by local tusk hunters in 2010. The hunters soon handed it over to scientists, who were excited to see its exquisite level of preservation, with skin, muscle tissue, and even reddish hair intact. Later research showed that, while full cloning was impossible, Yuka’s DNA was in such good condition that some cell nuclei could even begin limited activity when placed inside mouse eggs.

Now, a team has successfully sequenced Yuka’s RNA—a feat many researchers once thought impossible. Researchers at Stockholm University carefully ground up bits of muscle and other tissue from Yuka and nine other woolly mammoths, then used special chemical treatments to pull out any remaining RNA fragments, which are normally thought to be much too fragile to survive even a few hours after an organism has died. Scientists go to great lengths to extract RNA even from fresh samples, and most previous attempts with very old specimens have either failed or been contaminated.

A different view

The team used RNA-handling methods adapted for ancient, fragmented molecules. Their scientific séance allowed them to explore information that had never been accessible before, including which genes were active when Yuka died. In the creature’s final panicked moments, its muscles were tensing and its cells were signaling distress—perhaps unsurprising since Yuka is thought to have died as a result of a cave lion attack.

It’s an exquisite level of detail, and one that scientists can’t get from just analyzing DNA. “With RNA, you can access the actual biology of the cell or tissue happening in real time within the last moments of life of the organism,” said Emilio Mármol, a researcher who led the study. “In simple terms, studying DNA alone can give you lots of information about the whole evolutionary history and ancestry of the organism under study. “Obtaining this fragile and mostly forgotten layer of the cell biology in old tissues/specimens, you can get for the first time a full picture of the whole pipeline of life (from DNA to proteins, with RNA as an intermediate messenger).”

World’s oldest RNA extracted from ice age woolly mammoth Read More »

New study settles 40-year debate: Nanotyrannus is a new species

Nanotyrannus, paleontology, Science, Taxonomy, tyrannosaurs / DJ Henderson / October 30, 2025

For four decades, a frequently acrimonious debate has raged in paleontological circles about the correct taxonomy for a handful of rare fossil specimens. One faction insisted the fossils were juvenile Tyrannosaurus rex; the other argued that they represented a new species dubbed Nanotyrannus lancensis. Now, paleontologists believe they have settled the debate once and for all due to a new analysis of a well-preserved fossil.

The verdict: It is indeed a new species, according to a new paper published in the journal Nature. The authors also reclassified another specimen as a second new species, distinct from N. lancensis. In short, Nanotyrannus is a valid taxon and contains two species.

“This fossil doesn’t just settle the debate,” said Lindsay Zanno, a paleontologist at North Carolina State University and head of paleontology at North Carolina Museum of Natural Sciences. “It flips decades of T. rex research on its head.” That’s because paleontologists have relied on such fossils to model the growth and behavior of T. rex. The new findings suggest that there could have been multiple tyrannosaur species and that paleontologists have been underestimating the diversity of dinosaurs from this period.

Our story begins in 1942, when the fossilized skull of a Nanotyrannus, nicknamed Chomper, was excavated in Montana by a Cleveland Museum of Natural History expedition. Originally, paleontologists thought it belonged to a Gorgosaurus, but a 1965 paper challenged that identification and argued that the skull belonged to a juvenile T. rex. It wasn’t until 1988 that scientists proposed that the skull was actually that of a new species, Nanotyrannus. It’s been a constant back-and-forth ever since.

As recently as 2020, a highly influential paper claimed that Nanotyrannus was definitively a juvenile T. Rex. Yet a substantial number of paleontologists still believed it should be classified as a distinct species. A January 2024 paper, for instance, came down firmly on the Nanotyrannus side of the debate. Co-authors Nicholas Longrich of the University of Bath and Evan Saitta of the University of Chicago measured the growth rings in Nanotyrannus bones and concluded the animals were nearly fully grown.

Dueling dinosaurs

Lindsay Zanno, associate research professor at North Carolina State University and head of paleontology at the North Carolina Museum of Natural Sciences, with the Dueling Dinosaurs fossil. — Lindsay Zanno of North Carolina State University, who also heads paleontology at the North Carolina Museum of Natural Sciences, with the “dueling dinosaurs” fossil. Credit: N.C. State University/CC BY-NC-ND

Furthermore, there was no evidence of hybrid fossils combining features of both Nanotyrannus and T. rex, which one would expect if the former were a juvenile version of the latter. Longrich and Saitta had also discovered a skull bone, archived in a San Francisco museum, that did belong to a juvenile T. rex, and they were able to do an anatomical comparison. They argued that Nanotyrannus had a lighter build, longer limbs, and larger arms than a T. rex and likely was smaller, faster, and more agile.

New study settles 40-year debate: Nanotyrannus is a new species Read More »

Dinosaurs may have flourished right up to when the asteroid hit

asteroid, Biology, dinosaurs, evolution, Impact, paleontology, Science / Mike M. / October 25, 2025

That seemingly changes as of now, with new argon dating of strata from the Naashoibito Member in the San Juan Basin of present-day New Mexico. Many dinosaur fossils have been obtained from this region, and we know the site differs from the sort of ecosystem found at Hell Creek. But it was previously thought to date back closer to a million years before the mass extinction. The new dates, plus the alignment of magnetic field reversals, tell us that the ecosystem was a contemporary of the one in Hell Creek, and dates to the last few hundred thousand years prior to the mass extinction.

Diverse ecosystems

The fossils at Naashoibito have revealed an ecosystem we now label the “Alamo Wash local fauna.” And they’re fairly distinct from the ones found in Wyoming, despite being just 1,500 kilometers further south. Analyzing the species present using ecological measures, the researchers found that dinosaurs formed two “bioprovinces” in the late Cretaceous—essentially, there were distinct ecosystems present in the northern and southern areas.

This doesn’t seem to be an artifact of the sites, as mammalian fossils seem to reflect a single community across both areas near the mass extinction, but had distinct ecologies both earlier and after. The researchers propose that temperature differences were the key drivers of the distinction, something that may have had less of an impact on mammals, which are generally better at controlling their own temperatures.

Overall, the researchers conclude that, rather than being dominated by a small number of major species, “dinosaurs were thriving in New Mexico until the end of the Cretaceous.”

While this speaks directly to the idea that limited diversity may have primed the dinosaurs for extinction, it also may have implications for the impact of the contemporaneous eruptions in the Deccan Traps. If these were having a major global impact, then it’s a bit unlikely that dinosaurs would be thriving anywhere.

Even with the new data, however, our picture is still limited to the ecosystems present on the North American continent. We do have fossils from elsewhere, but they’re not exactly dated. There are some indications of dinosaurs in the late Cretaceous in Europe and South America, but we don’t have a clear picture of the ecosystems in which they were found. So, while these findings help clarify the diversity of dinosaurs in the time leading up to their extinction, there’s still a lot left to learn.

Science, 2025. DOI: 10.1126/science.adw3282 (About DOIs).

Dinosaurs may have flourished right up to when the asteroid hit Read More »

150 million-year-old pterosaur cold case has finally been solved

Biology, fossils, paleontology, pterosaurs, Science / Shannon Garcia / September 28, 2025

Smyth thinks that so few adults show up on the fossil record in this region not only because they were more likely to survive, but also because those that couldn’t were not buried as quickly. Carcasses would float on the water anywhere from days to weeks. As they decomposed, parts would fall to the lagoon bottom. Juveniles were small enough to be swept under and buried quickly by sediments that would preserve them.

Cause of death

The humerus fractures found in Lucky I and Lucky II were especially significant because forelimb injuries are the most common among existing flying vertebrates. The humerus attaches the wing to the body and bears most flight stress, which makes it more prone to trauma. Most humerus fractures happen in flight as opposed to being the result of a sudden impact with a tree or cliff. And these fractures were the only skeletal trauma seen in any of the juvenile pterosaur specimens from Solnhofen.

Evidence suggesting the injuries to the two fledgling pterosaurs happened before death includes the displacement of bones while they were still in flight (something recognizable from storm deaths of extant birds and bats) and the smooth edges of the break, which happens in life, as opposed to the jagged edges of postmortem breaks. There were also no visible signs of healing.

Storms disproportionately affected flying creatures at Solnhofen, which were often taken down by intense winds. Many of Solnhofen’s fossilized vertebrates were pterosaurs and other winged species such as bird ancestor Arachaeopteryx. Flying invertebrates were also doomed.

Even marine invertebrates and fish were threatened by storm conditions, which churned the lagoons and brought deep waters with higher salt levels and low oxygen to the surface. Anything that sank to the bottom was exceptionally preserved because of these same conditions, which were too harsh for scavengers and paused decomposition. Mud kicked up by the storms also helped with the fossilization process by quickly covering these organisms and providing further protection from the elements.

“The same storm events responsible for the burial of these individuals also transported the pterosaurs into the lagoonal basins and were likely the primary cause of their injury and death,” Smyth concluded.

Although Lucky I and Lucky II were decidedly unlucky, the exquisite preservation of their skeletons that shows how they died has finally allowed researchers to solve a case that went cold for over a hundred thousand years.

Current Biology, 2025. DOI: 10.1016/j.cub.2025.08.006

150 million-year-old pterosaur cold case has finally been solved Read More »

New dinosaur species is the punk rock version of an ankylosaur

ankylosaurs, Biology, dinosaurs, evolution, paleontology, Science / Beth Washington / August 28, 2025

And we have known for sure that the armor was around back then, given that we’ve found the skin-derived osteoderms that comprise the armor in Jurassic deposits. But with little more than a rib and a handful of mouth parts to go on, it wasn’t really possible to say much more than that.

Until now, that is. Because the new Spicomellus remains show extremely clearly that the armor of ankylosaurs got less elaborate over time.

The small, solid-looking spikes found along the edges of later ankylosaurs? Forget those. Spicomellus had a back that was probably bristling with sharper spines, along with far larger ones along its outer edges. Each rib appears to have generated as many as six individual spikes. At a handful of locations, these spikes extended out to nearly a meter, looking more like lances than anything needed to ward off a close-in attack.

And the largest of these were along its neck. On the upper surface of its neck, several osteoderms fused to form a massive half-collar of bone and then extended out five or more individual spikes, each among the longest on the animal’s body. And there were three of these structures along the neck. “No known ankylosaur possesses any condition close to the extremely long pairs of spines on the cervical half-ring of Spicomellus,” its discoverers note.

As if its hedgehog-on-acid appearance weren’t enough, handles present on the tail vertebrae suggest that it also had a weaponized tail. All told, the researchers sum things up by saying, “The new specimen reveals extreme dermal armour modifications unlike those of any other vertebrate, extinct or extant, which fall far outside of the range of morphologies shown by other armoured dinosaurs.”

Out go the hypotheses

Because it’s so unusual, the skeleton’s characteristics are difficult to place within a neat family tree of the ankylosaurs. The researchers conclude that some details of its skeleton do suggest Spicomellus groups among the ankylosaurs and conclude that it’s probably an early branch from the main lineage. But without any other significant examples from the lineage at that time, it’s an extremely tentative conclusion. Still, the alternative is that this thing is unrelated to the only other organisms that share at least a few of its bizarre features, which is a difficult idea to swallow.

New dinosaur species is the punk rock version of an ankylosaur Read More »

For giant carnivorous dinosaurs, big size didn’t mean a big bite

Biology, Biomechanics, carnivores, dinosaurs, fossils, paleontology, Science / DJ Henderson / August 9, 2025

“And then you have the Spinosaurus which was kind of weird in general,” Rowe says. “There was a study by Dave Hone and Tom Holtz about how it was waiting on the shorelines, waiting for food to go by that it could fish out.” But Spinosaurus’ foraging wasn’t limited to fishing. There was a pterosaur found preserved in its stomach and there were iguanodon remains found in the maw of a Baryonyx, another large carnivore belonging to the same lineage as the Spinosaurus. “They had great diversity in their diet. They were generalists, but our results show they weren’t these massive bone-crunching predators like the T. rex,” Rowe says. Because the T. rex was just built different.

King of the Cretaceous jungle

The Tyranosauroidea lineage had stiff, akinetic skulls, meaning they had very little mobility in the joints. The T. rex skull could and most likely did withstand very high stress as the animal pursued a “high stress, high power” strategy, entirely different from other large carnivores. “They were very much like big crocodiles with extremely strong, reinforced jaws and powerful muscles that could pulverize bones,” Rowe claims.

The T. rex, he argued, was a specialist—an ambush predator that attacked large, highly mobile prey, aiming to subdue it with a single bite. “And we have fossil evidence of that,” Rowe says. “In the Museum of Natural History in New York, there is a Hadrosaur, a large herbivorous dinosaur with a duck-like beak, and there’s a T. rex tooth embedded in its back.” This, he thinks, means the T. rex was actively preying on this animal, especially since there are healing marks around the stuck tooth. “Even with this super strong bite, the T. rex wasn’t always successful,” Rowe adds.

Still, the fight with the Spinosaurus most likely wouldn’t go the way it did in Jurassic Park III. “The T. rex was built to fight like that; the Spinosaurus really wasn’t”, Rowe says.

Current Biology, 2025. DOI: 10.1016/j.cub.2025.06.051

For giant carnivorous dinosaurs, big size didn’t mean a big bite Read More »

We probably inherited our joints from… a fish

Biology, developmental biology, evolution, joints, paleontology, Science, synovial joints / Mike M. / March 23, 2025

What do we have in common with fish, besides being vertebrates? The types of joints we (and most vertebrates) share most likely originated from the same common ancestor. But it’s not a feature that we share with all vertebrates.

Humans, other land vertebrates, and jawed fish have synovial joints. The lubricated cavity within these joints makes them more mobile and stable because it allows for bones or cartilage to slide against each other without friction, which facilitates movement.

The origin of these joints was uncertain. Now, biologist Neelima Sharma of the University of Chicago and her colleagues have taken a look at which fish form this type of joint. Synovial joints are known to be present in jawed but not jawless fish. This left the question of whether they are just a feature of bony skeletons in general or if they are also found in fish with cartilaginous skeletons, such as sharks and skates (there are no land animals with cartilaginous skeletons).

As Sharma and her team found, cartilaginous fish with jaws, such as the skate embryos they studied, do develop these joints, while jawless fish, such as lampreys and hagfish, lack them.

So what could this mean? If jawed fish have synovial joints in common with all jawed vertebrates, including us, it must have evolved in our shared ancestor.

Something fishy in our past

While the common ancestor of vertebrates with synovial joints is still a mystery, the oldest specimen with evidence of these joints is Bothriolepis canadensis, a fish that lived about 387 to 360 million years ago during the Middle to Late Devonian period.

When using CT scanning to study a Bothriolepis fossil, Sharma observed a joint cavity between the shoulder and pectoral fin. Whether the cavity was filled with synovial fluid or cartilage is impossible to tell, but either way, she thinks it appears to have functioned like a synovial joint would. Fossils of early jawless fish, in contrast, lack any signs of synovial joints.

We probably inherited our joints from… a fish Read More »

Even the worst mass extinction had its oases

Biology, Ecology, end-permian, Great Dying, mass extinction, paleontology, refugee, Science / Kelly Newman / March 18, 2025

Some earlier plants might not have made it through the extinction since rock layers from the onset of the End-Permian Mass Extinction showed a decrease in pollen and spores, as well as fewer plant species. Other species were scarce because they had not been as well-preserved as others; the team did not automatically assume the scarcity of a plant that did not fossilize meant it had gone extinct.

While there were plant species that ended up being victims of the Great Dying, analysis of species through spore and pollen told the team that only about 21 percent of them succumbed to extinction.

Life will not be contained

The fossils also revealed the presence of plant species known to grow near lakes, which meant an environment that most likely provided drinking water for land-dwelling animals. Fossilized spores farther from what were once the banks of an ancient lake or the edge of a lakeplain suggest it was surrounded by a forest of gymnospermous trees, such as conifers or ginkgo, and ferns.

Because the researchers found so many spores from plant species known to grow in humid climates, they think the regional climate before the extinction was either humid or sub-humid, with plenty of rain. It was a lush environment that would see dry periods during the mass extinction event, but not be completely devastated.

Despite some species of plants vanishing, those that were found to have survived during and after the extinction mostly belonged to conifers and pteridosperms (now-extinct plants similar to ferns), which showed “a remarkable ability to adapt to drought,” as Liu and his team said in the same study.

The drought turned out to be only temporary. Younger rock layers were found to contain a greater abundance of pollen and spores from species that grew during the extinction event. The types of plants represented suggest a climate that had returned to subhumid and was more habitable.

Fossils of animals found at the site support its role as a haven for life. From the herbivorous Lystrosaurus (not a dinosaur), which looked something like a walrus with legs and a shovel face, to the carnivorous chroniosuchians that resembled giant lizards and fed on insects and small amphibians, the refugium in what is now Xinjiang kept life going.

Both flora and fauna would soon spread across terrestrial environments once again. Life on land flourished only 75,000 years after the End-Permian Mass Extinction, so life really does find a way.

Science Advances, 2025. DOI: 10.1126/sciadv.ads5614

Even the worst mass extinction had its oases Read More »

Study: Megalodon’s body shape was closer to a lemon shark

aquatic animals, megalogon, paleontology, Science / Beth Washington / March 10, 2025

the mighty, mighty megalodon

Also: Baby megalodons were likely the size of great white sharks and capable of hunting marine mammals

The giant extinct shark species known as the megalodon has captured the interest of scientists and the general public alike, even inspiring the 2018 blockbuster film The Meg. The species lived some 3.6 million years ago and no complete skeleton has yet been found. So there has been considerable debate among paleobiologists about megalodon’s size, body shape and swimming speed, among other characteristics.

While some researchers have compared megalodon to a gigantic version of the stocky great white shark, others believe the species had a more slender body shape. A new paper published in the journal Palaeontologia Electronica bolsters the latter viewpoint, also drawing conclusions about the megalodon’s body mass, swimming speed (based on hydrodynamic principles), and growth patterns.

As previously reported, the largest shark alive today, reaching up to 20 meters long, is the whale shark, a sedate filter feeder. As recently as 4 million years ago, however, sharks of that scale likely included the fast-moving predator megalodon (formally Otodus megalodon). Due to incomplete fossil data, we’re not entirely sure how large megalodons were and can only make inferences based on some of their living relatives.

Thanks to research published in 2023 on its fossilized teeth, we’re now fairly confident that megalodon shared something else with these relatives: it wasn’t entirely cold-blooded and kept its body temperature above that of the surrounding ocean. Most sharks, like most fish, are ectothermic, meaning that their body temperatures match those of the surrounding water. But a handful of species, part of a group termed mackerel sharks, are endothermic: They have a specialized pattern of blood circulation that helps retain some of the heat their muscles produce. This enables them to keep some body parts at a higher temperature than their surroundings.

Of particular relevance to this latest paper is a 2022 study by Jack Cooper of Swansea University in the UK and his co-authors. In 2020, the team reconstructed a 2D model of the megalodon, basing the dimensions on similar existing shark species. The researchers followed up in 2022 with a reconstructed 3D model, extrapolating the dimensions from a megalodon specimen (a vertebral column) in Belgium. Cooper concluded that a megalodon would have been a stocky, powerful shark—measuring some 52 feet (16 meters) in length with a body mass of 67.86 tons—able to execute bursts of high speed to attack prey, much like the significantly smaller great white shark.

(H) One of the largest vertebrae of Otodus meg- alodon; (I and J) CT scans showing cross-sectional views. — (H) One of the largest vertebrae of *Otodus megalodon*; (I and J) CT scans showing cross-sectional views. Credit: Shimada et al., 2025

Not everyone agreed, however, Last year, a team of 26 shark experts led by Kesnshu Shimada, a paleobiologist at DePaul University, further challenged the great white shark comparison, arguing that the super-sized creature’s body was more slender and possibly even longer than researchers previously thought. The team concluded that based on the spinal column, the combination of a great white build with the megalodon’s much longer length would have simply proved too cumbersome.

A fresh approach

Now Shimada is back with a fresh analysis, employing a new method that he says provides independent lines of evidence for the megalodon’s slender build. “Our new study does not use the modern great white shark as a model, but rather simply asks, ‘How long were the head and tail based on the trunk [length] represented by the fossil vertebral column?’ using the general body plan seen collectively in living and fossil sharks,” Shimada told Ars.

Shimada and his co-authors measured the proportions of 145 modern and 20 extinct species of shark, particularly the head, trunk, and tail relative to total body length. Megalodon was represented by a Belgian vertebral specimen. The largest vertebra in that specimen measured 15.5 centimeters (6 inches) in diameter, although there are other megalodon vertebrae in Denmark, for example, with diameters as much as 23 centimeters (9 inches).

Based on their analysis, Shimada et al, concluded that, because the trunk section of the Belgian specimen measured 11 meters, the head and tail were probably about 1.8 meters (6 feet) and 3.6 meters (12 feet) long, respectively, with a total body length of 16.4 meters (54 feet) for this particularly specimen. That means the Danish megalodon specimens could have been as long as 24.3 meters (80 feet). As for body shape, taking the new length estimates into account, the lemon shark appears to be closest modern analogue. “However, the exact position and shape of practically all the fins remain uncertain,” Shimada cautioned. “We are only talking about the main part of the body.”

Revised tentative body outline of 24.3 meters (80 feet) extinct megatooth shark, Otodus megalodon. — Credit: DePaul University/Kenshu Shimada

The team also found that a 24.3-meter-long megalodon would have weighed a good 94 tons with an estimated swimming speed of 2.1-3.5 KPM (1.3-2.2 MPH). They also studied growth patterns evident in the Belgian vertebrae, concluding that the megalodon would give live birth and that the newborns would be between 3.6 to 3.9 meters (12-13 feet) long—i.e., roughly the size of a great white shark. The authors see this as a refutation of the hypothesis that megalodons relied on nursery areas to rear their young, since a baby megalodon would be quite capable of hunting and killing marine mammals based on size alone.

In addition, “We unexpectedly unlocked the mystery of why certain aquatic vertebrates can attain gigantic sizes while others cannot,” Shimada said. “Living gigantic sharks, such as the whale shark and basking shark, as well as many other gigantic aquatic vertebrates like whales have slender bodies because large stocky bodies are hydrodynamically inefficient for swimming.”

That’s in sharp contrast to the great white shark, whose stocky body becomes even stockier as it grows. “It can be ‘large’ but cannot [get] past 7 meters (23 feet) to be ‘gigantic’ because of hydrodynamic constraints,” said Shimada. “We also demonstrate that the modern great white shark with a stocky body hypothetically blown up to the size of megalodon would not allow it to be an efficient swimmer due to the hydrodynamic constraints, further supporting the idea that it is more likely than not that megalodon must have had a much slenderer body than the modern great white shark.”

Shimada emphasized that their interpretations remain tentative but they are based on hard data and make for useful reference points for future research.

An “exciting working hypothesis”

For his part, Cooper found a lot to like in Shimada et al.’s latest analysis. “I’d say everything presented here is interesting and presents an exciting working hypothesis but that these should also be taken with a grain of salt until they can either be empirically tested, or a complete skeleton of megalodon is found to confirm one way or the other,” Cooper told Ars. “Generally, I appreciate the paper’s approach to its body size calculation in that it uses a lot of different shark species and doesn’t make any assumptions as to which species are the best analogues to megalodon.”

Shark biologists now say a lemon shark, like this one, is a better model of the extinct megalodon's body than the great white shark. — Shark biologists now say a lemon shark, like this one, is a better model of the extinct megalodon’s body than the great white shark. Credit: Albert Kok

Cooper acknowledged that it makes sense that a megalodon would be slightly slower than a great white given its sheer size, “though it does indicate we’ve got a shark capable of surprisingly fast speeds for its size,” he said. As for Shimada’s new growth model, he pronounced it “really solid” and concurred with the findings on birthing with one caveat. “I think the refutation of nursery sites is a bit of a leap, though I understand the temptation given the remarkably large size of the baby sharks,” he said. “We have geological evidence of multiple nurseries—not just small teeth, but also geological evidence of the right environmental conditions.”

He particularly liked Shinada et al.’s final paragraph. “[They] call out ‘popular questions’ along the lines of, ‘Was megalodon stronger than Livyatan?'” said Cooper. “I agree with the authors that these sorts of questions—ones we all often get asked by ‘fans’ on social media—are really not productive, as these unscientific questions disregard the rather amazing biology we’ve learned about this iconic, real species that existed, and reduce it to what I can only describe as a video game character.”

Regardless of how this friendly ongoing debate plays out, our collective fascination with megalodon is likely to persist. “It’s the imagining of such a magnificently enormous shark swimming around our oceans munching on whales, and considering that geologically speaking this happened in the very recent past,” said Cooper of the creature’s appeal. “It really captures what evolution can achieve, and even the huge size of their teeth alone really put it into perspective.”

DOI: Palaeontologia Electronica, 2025. 10.26879/1502 (About DOIs).

Jennifer is a senior writer at Ars Technica with a particular focus on where science meets culture, covering everything from physics and related interdisciplinary topics to her favorite films and TV series. Jennifer lives in Baltimore with her spouse, physicist Sean M. Carroll, and their two cats, Ariel and Caliban.

Study: Megalodon’s body shape was closer to a lemon shark Read More »

Lizards and snakes are 35 million years older than we thought

Biology, fossils, lizards, paleontology, reptiles, Science / 9u50fv / December 6, 2024

Lizards are ancient creatures. They were around before the dinosaurs and persisted long after dinosaurs went extinct. We’ve now found they are 35 million years older than we thought they were.

Cryptovaranoides microlanius was a tiny lizard that skittered around what is now southern England during the late Triassic, around 205 million years ago. It likely snapped up insects in its razor teeth (its name means “hidden lizard, small butcher”). But it wasn’t always considered a lizard. Previously, a group of researchers who studied the first fossil of the creature, or holotype, concluded that it was an archosaur, part of a group that includes the extinct dinosaurs and pterosaurs along with extant crocodilians and birds.

Now, another research team from the University of Bristol has analyzed that fossil and determined that Cryptovaranoides is not an archosaur but a lepidosaur, part of a larger order of reptiles that includes squamates, the reptile group that encompasses modern snakes and lizards. It is now also the oldest known squamate.

The misunderstandings about this species all come down to features in its bones that are squamate apomorphies. These are traits unique to squamates that were not present in their ancestral form, but evolved later. Certain forelimb bones, skull bones, jawbones, and even teeth of Cryptovaranoides share characteristics with those from both modern and extinct lizards.

Wait, what is that thing?

So what does the new team argue that the previous team that studied Cryptovaranoides gets wrong? The new paper argues that the interpretation of a few bones in particular stand out, especially the humerus and radius.

In the humerus of this lizard, structures called the ectepicondylar and entepicondylar foramina, along with the radial condyle, were either not considered or may have been misinterpreted. The entepicondylar foramen is an opening in the far end of the humerus, which is an upper arm bone in humans and upper forelimb bone in lizards. The ectepicondylar foramen is a structure on the outer side of the humerus where the extensor muscles attach, helping a lizard bend and straighten its legs. Both features are “often regarded as key lepidosaur and squamate characteristics,” the Bristol research team said in a study recently published in Royal Society Open Science.

Lizards and snakes are 35 million years older than we thought Read More »

What fossilized dino feces can tell us about their rise to dominance

coprolites, dinosaurs, evolutionary biology, food webs, fossilized feces, Jurassic, paleontology, Science, Triassic / Shannon Garcia / November 27, 2024

Paleontologists have long puzzled over how the dinosaurs—originally relatively small and of minor importance to the broader ecosystem—evolved to become the dominant species some 30 million years later. Fossilized feces and vomit from dinosaurs might hold important clues to how and why this evolutionary milestone came about, according to a new paper published in the journal Nature.

Co-author Martin Qvarnström, an evolutionary biologist with Uppsala University in Sweden, and his collaborators studied trace fossils known as bromalites, a designation that includes coprolites as well as vomit or other fossilized matter from an organism’s digestive tract. As previously reported, coprolites aren’t quite the same as paleofeces, which retain a lot of organic components that can be reconstituted and analyzed for chemical properties. Coprolites are fossils, so most organic components have been replaced by mineral deposits like silicate and calcium carbonates.

For archaeologists keen on learning more about the health and diet of past populations—as well as how certain parasites evolved in the evolutionary history of the microbiome—coprolites and paleofeces can be a veritable goldmine of information. For instance, in 2021 we reported on an analysis of preserved paleo-poop revealing that ancient Iron Age miners in what is now Austria were fond of beer and blue cheese.

If a coprolite contains bone fragments, chances are the animal who excreted it was a carnivore, and tooth marks on those fragments can tell us something about how the animal may have eaten its prey. The size and shape of coprolites can also yield useful insights. If a coprolite is spiral-shaped, for instance, it might have been excreted by an ancient shark, since some modern fish (like sharks) have spiral-shaped intestines.

A tale of two models

Excavations in the Late Triassic locality at Lisowice, Poland. The site yielded a large number of coprolites of predators and herbivores. Credit: Krystian Balanda

Qvarnström et al. were keen to test two competing hypotheses about the dinosaurs’ rise to dominance from the Late Triassic Period (237 million to 201 million years ago) to the onset of the Jurassic Period between 201 million to 145 million years ago. “No single hypothesis seems capable of explaining the rise of dinosaurs fully and critical questions about how dinosaurs established their dynasty on land remain largely unanswered,” the authors wrote about their research objectives.

One hypothesis cites evolutionary competition—the traditional “competitive replacement” model—as a driving factor, in which dinosaurs were better equipped to survive thanks to superior physiologies, anatomical adaptations, and feeding habits. Alternatively the “opportunistic replacement” model suggests that the dinosaurs were better able to adapt to a rapidly changing environment brought about by random processes—volcanic eruptions, climate change, or other catastrophic events that led to the decline and/or extinction of other species.

What fossilized dino feces can tell us about their rise to dominance Read More »