Different tracks, same dinosaurs: Researchers dig deeper into dinosaur movements

When picturing dinosaur tracks, most people imagine a perfectly preserved mold of a foot on firm layer of earth. But what if that dinosaur was running through mud, sinking several inches — or even up to their ankles — into the ground as it moved?

Using sophisticated X-ray-based technology, a team of Brown University researchers tracked the movements of guineafowl to investigate how their feet move below ground through various substrates and what those findings could mean for understanding fossil records left behind by dinosaurs.

They found that regardless of the variability in substrates, or the guineafowl moving at different speeds, sinking at different depths or engaging in different behaviors, the birds’ overall foot movement remained the same: The toes spread as they stepped onto the substrate surface, remained spread as the foot sank, collapsed and drew back as they were lifted from the substrate, and exited the substrate in front of the point of entry, creating a looping pattern as they walked.

And part of what that means is that fossilized dinosaur tracks that look distinct from each other, and appear to be from different species, might instead come from the same dinosaurs.

“This is the first study that’s really shown how the bird foot is moving below ground, showing the patterns of this subsurface foot motion and allowing us to break down the patterns that we’re seeing in a living animal that has feet similar to those of a dinosaur,” said Morgan Turner, a Ph.D. candidate at Brown in ecology and evolutionary biology and lead author of the research. “Below ground, or even above ground, they’re responding to these soft substrates in a very similar way, which has potentially important implications for our ability to study the movement of these animals that we can’t observe directly anymore.”

The findings were published on Wednesday, July 1, in the Royal Society journal Biology Letters.

To make the observations, Turner and her colleagues, Professor of Biology and Medical Science Stephen Gatesy and Peter Falkingham, now at Liverpool John Moores University, used a 3D-imaging technology developed at Brown called X-ray Reconstruction of Moving Morphology (XROMM). The technology combines CT scans of a skeleton with high-speed X-ray video, aided by tiny implanted metal markers, to create visualizations of how bones and muscles move inside humans and animals. In the study, the team used XROMM to watch guineafowl move through substrates of different hydration and compactness, analyzing how their feet moved underground and the tracks left behind.

Sand, typically a dense combination of quartz and silica, does not lend itself well to X-ray imaging, so the team used poppy seeds to emulate sand. Muds were made using small glass bubbles, adding various amount of clay and water across 107 trials to achieve different consistencies and realistic tracks.

They added metal markers underneath the claws of the guineafowl to allow for tracking in 3D space. It’s these claw tips that the researchers think are least disturbed by mud flow and other variables that can impact and distort the form of the track.

Despite the variation, the researchers observed a consistent looping pattern.

“The loops by themselves I don’t think are that interesting,” Gatesy said. “People are like, ‘That’s nice. Birds do this underground. So what?’ It was only when [Turner] went back into it and said, ‘What if we slice those motion trails at different depths as if they were footprints?’ Then we made the nice connection to the fossils.”

By “slicing” through the 3D images of the movement patterns at different depths, the researchers found similarities between the guineafowl tracks and fossilized dinosaur tracks.

“We don’t know what these dinosaurs were doing, we don’t know what they were walking through exactly, we don’t know how big they were or how deep they were sinking, but we can make this really strong connection between how they were moving and some level of context for where this track is being sampled from within that movement,” Turner said.

By recognizing the movement patterns, as well as the entry and exit point of the foot through various substrates, the team says they’re able to gain a better understanding of what a dinosaur track could look like.

“You end up generating this big diversity of track shapes from a very simple foot shape because you’re sampling at different depths and it’s moving in complicated ways,” Gatesy said. “Do we really have 40 different kinds of creatures, each with a differently shaped foot, or are we looking at some more complicated interaction that leaves behind these remnants that are partly anatomical and partly motion and partly depth?”

To further their research, the team spent time at the Beneski Museum of Natural History at Amherst College in Massachusetts, which is home to an expansive collection of penetrative tracks discovered in the 1800s by geologist Edward Hitchcock.

Hitchcock originally believed that his collection housed fossil tracks from over 100 distinct animals. Because of the team’s work with XROMM, Gatesy now thinks it’s possible that at least half of those tracks are actually from the same dinosaurs, just moving their feet in slightly different ways or sampled at slightly different depths.

“Going to museum together and being able to pick out these features and say, ‘We think this track is low in the loop and we think this one is high,’ that was the biggest moment of insight for me,” Turner said.

Turner says she hopes their research can lead to a greater interest in penetrative tracks, even if they seem a little less pretty or polished than the tracks people are used to seeing in museums.

“They have so much information in them,” Turner said, “and I hope that this gives people a lens, a new way to view these footprints and appreciate the movement preserved within in them.”

This work was supported by the US National Science Foundation (EAR 1452119 to SMG and PLF; IOS 0925077 to SMG), a Marie Curie International Outgoing Fellowship within the 7th European Framework Programme to PLF, and the Bushnell Research and Education Fund to MLT.


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Tiny Japanese dinosaur eggs help unscramble Cretaceous ecosystem

When most of us think of dinosaurs, we envision large, lumbering beasts, but these giants shared their ecosystems with much smaller dinosaurs, the smaller skeletons of which were generally less likely to be preserved. The fossilized egg shells of these small dinosaurs can shed light on this lost ecological diversity.

Led by the University of Tsukuba, researchers scoured an exceptional fossil egg site first discovered in 2015 in Hyogo Prefecture, southwestern Japan, and reported their findings in a new study published in Cretaceous Research.

The Kamitaki Egg Quarry, found in a red-brown mudstone layer of the Ohyamashimo Formation, deposited in an Early Cretaceous (about 110 million years old) river flood plain, was carefully and intensively excavated in the winter of 2019, and yielded over 1300 egg fossils. Most were isolated fragments, but there were a few partial and almost complete eggs.

According to lead author Professor Kohei Tanaka, “our taphonomic analysis indicated that the nest we found was in situ, not transported and redeposited, because most of the eggshell fragments were positioned concave-up, not concave-down like we see when egg shells are transported.”

Most of these fossil eggs belong to a new egg genus and species, called Himeoolithus murakamii, and are exceptionally small, with an estimated mass of 9.9 grams — about the size of a modern quail egg. However, biological classification analysis implies that the eggs belonged not to early birds, but to their cousins, the non-avian theropod dinosaurs (the group that includes well-known carnivores like Tyrannosaurus and Velociraptor). That puts Himeoolithus murakamii among the smallest non-avian theropod eggs reported to date. These tiny eggs were notably elongated in shape — unusual for similarly small eggs among Cretaceous birds, but typical among larger non-avian theropod eggs.

In addition to the abundant Himeoolithus murakamii egg shells, five more ootaxa (distinct types of egg fossils) were recognized in the Kamitaki locality. All of these ootaxa belonged to small non-avian theropods.

As Professor Tanaka explains, “the high diversity of these small theropod eggs makes this one of the most diverse Early Cretaceous egg localities known. Small theropod skeletal fossils are quite scarce in this area. Therefore, these fossil eggs provide a useful window into the hidden ecological diversity of dinosaurs in the Early Cretaceous of southwestern Japan, as well as into the nesting behavior of small non-avian theropods.”


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300-million-year-old fish resembles a sturgeon but took a different evolutionary path

Sturgeon, a long-lived, bottom-dwelling fish, are often described as “living fossils,” owing to the fact that their form has remained relatively constant, despite hundreds of millions of years of evolution.

In a new study in the Zoological Journal of the Linnean Society, researchers led by Jack Stack, a 2019 University of Pennsylvania graduate, and paleobiologist Lauren Sallan of Penn’s School of Arts & Sciences, closely examine the ancient fish species Tanyrhinichthys mcallisteri, which lived around 300 million years ago in an estuary environment in what is today New Mexico. Although they find the fish to be highly similar to sturgeons in its features, including its protruding snout, they show that these characteristics evolved in a distinct evolutionary path from those species that gave rise to modern sturgeons.

The find indicates that, although ancient, the features that enabled Tanyrhinichthys to thrive in its environment arose multiple times in different fish lineages, a burst of innovation that was not previously fully appreciated for fish in this time period.

“Sturgeon are considered a ‘primitive’ species, but what we’re showing is that the sturgeon lifestyle is something that’s been selected for in certain conditions and has evolved over and over again,” says Sallan, senior author on the work.

“Fish are very good at finding solutions to ecological problems,” says Stack, first author on the study, who worked on the research as a Penn undergraduate and is now a graduate student at Michigan State University. “This shows the degree of both innovation and convergence that’s possible in fishes. Once their numbers got up large enough, they started producing brand new morphologies that we now see have evolved numerous times through the history of fishes, under similar ecological conditions. “

The first fossil of Tanyrhinichthys was found in 1984 in a fossil-rich area called the Kinney Brick Quarry, about a half hour east of Albuquerque. The first paleontologist to describe the species was Michael Gottfried, a Michigan State faculty member who now serves as Stack’s advisor for his master’s degree.

“The specimen looks like someone found a fish and just pulled on the front of its skull,” Stack says. Many modern fish species, from the swordfish to the sailfish, have protuberant snouts that extend out in front of them, often aiding in their ability to lunge at prey. But this characteristic is much rarer in ancient fishes. In the 1980s when Gottfried described the initial specimen, he posited that the fish resembled a pike, an ambush predator with a longer snout.

During the last decade, however, several more specimens of Tanyrhinichthys have been found in the same quarry. “Those finds were an impetus for this project, now that we had better information on this enigmatic and strange fish,” Stack says.

At the time that Tanyrhinichthys roamed the waters, Earth’s continents were joined in the massive supercontinent called Pangea, surrounded by a single large ocean. But it was an ice age as well, with ice at both poles. Just before this period, the fossil record showed that ray-finned fishes, which now dominate the oceans, were exploding in diversity. Yet 300 million years ago, “it was like someone hit the pause button,” Sallan says. “There’s an expectation that there would be more diversity, but not much has been found, likely owing to the fact that there just hasn’t been enough work on this time period, especially in the United States, and particularly in the Western United States.”

Aiming to fill in some of these gaps by further characterizing Tanyrhinichthys, Stack, Sallan, and colleagues closely examined the specimens in detail and studied other species that dated to this time period. “This sounds really simple, but it’s obviously difficult in execution,” Stack notes, as fossils are compressed flat when they are preserved. The researchers inferred a three-dimensional anatomy using the forms of modern fishes to guide them.

What they noticed cast doubt on the conception of Tanyrhinichthys as resembling a pike. While a pike has an elongated snout with its jaws at the end of it, allowing it to rush its prey head-on, Tanyrhinichthys has an elongated snout with its jaws at the bottom.

“The whole form of this fish is similar to other bottom dwellers,” Stack says. Sallan also noticed canal-like structures on its snout concentrated in the top of its head, suggestive of the locations where sensory organs would attach. “These would have detected vibrations to allow the fish to consume its prey,” says Sallan.

The researchers noted that many of the species that dwelled in similar environments possessed longer snouts, which Sallan called “like an antenna for your face.”

“This also makes sense because it was an estuary environment,” Sallan says, “with large rivers feeding into it, churning up the water, and making it murky. Rather than using your eyesight, you have to use these other sensory organs to detect prey.”

Despite this, other features of the different ancient fishes’ morphology were so different from Tanyrhinichthys that they do not appear to have shared a lineage with one another, nor do modern sturgeon descend from Tanyrhinichthys. Instead the long snouts appear to be an example of convergent evolution, or many different lineages all arriving at the same innovation to adapt well to their environment.

“Our work, and paleontology in general, shows that the diversity of life forms that are apparent today has roots that extend back into the past,” says Stack.


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First egg from Antarctica is big and might belong to an extinct sea lizard

In 2011, Chilean scientists discovered a mysterious fossil in Antarctica that looked like a deflated football. For nearly a decade, the specimen sat unlabeled and unstudied in the collections of Chile’s National Museum of Natural History, with scientists identifying it only by its sci-fi movie-inspired nickname — “The Thing.”

An analysis led by researchers at The University of Texas at Austin has found that the fossil is a giant, soft-shell egg from about 66 million years ago. Measuring in at more than 11 by 7 inches, the egg is the largest soft-shell egg ever discovered and the second-largest egg of any known animal.

The specimen is the first fossil egg found in Antarctica and pushes the limits of how big scientists thought soft-shell eggs could grow. Aside from its astounding size, the fossil is significant because scientists think it was laid by an extinct, giant marine reptile, such as a mosasaur — a discovery that challenges the prevailing thought that such creatures did not lay eggs.

“It is from an animal the size of a large dinosaur, but it is completely unlike a dinosaur egg,” said lead author Lucas Legendre, a postdoctoral researcher at UT Austin’s Jackson School of Geosciences. “It is most similar to the eggs of lizards and snakes, but it is from a truly giant relative of these animals.”

A study describing the fossil egg was published in Nature on June 17.

Co-author David Rubilar-Rogers of Chile’s National Museum of Natural History was one of the scientists who discovered the fossil in 2011. He showed it to every geologist who came to the museum, hoping somebody had an idea, but he didn’t find anyone until Julia Clarke, a professor in the Jackson School’s Department of Geological Sciences, visited in 2018.

“I showed it to her and, after a few minutes, Julia told me it could be a deflated egg!” Rubilar-Rogers said.

Using a suite of microscopes to study samples, Legendre found several layers of membrane that confirmed that the fossil was indeed an egg. The structure is very similar to transparent, quick-hatching eggs laid by some snakes and lizards today, he said. However, because the fossil egg is hatched and contains no skeleton, Legendre had to use other means to zero in on the type of reptile that laid it.

He compiled a data set to compare the body size of 259 living reptiles to the size of their eggs, and he found that the reptile that laid the egg would have been more than 20 feet long from the tip of its snout to the end of its body, not counting a tail. In both size and living reptile relations, an ancient marine reptile fits the bill.

Adding to that evidence, the rock formation where the egg was discovered also hosts skeletons from baby mosasaurs and plesiosaurs, along with adult specimens.

“Many authors have hypothesized that this was sort of a nursery site with shallow protected water, a cove environment where the young ones would have had a quiet setting to grow up,” Legendre said.

The paper does not discuss how the ancient reptile might have laid the eggs. But the researchers have two competing ideas.

One involves the egg hatching in the open water, which is how some species of sea snakes give birth. The other involves the reptile depositing the eggs on a beach and hatchlings scuttling into the ocean like baby sea turtles. The researchers say that this approach would depend on some fancy maneuvering by the mother because giant marine reptiles were too heavy to support their body weight on land. Laying the eggs would require the reptile to wriggle its tail on shore while staying mostly submerged, and supported, by water.

“We can’t exclude the idea that they shoved their tail end up on shore because nothing like this has ever been discovered,” Clarke said.


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Tracking Australia’s gigantic carnivorous dinosaurs

North America had the T. rex, South America had the Giganotosaurus and Africa the Spinosaurus — now evidence shows Australia had gigantic predatory dinosaurs.

The discovery came in University of Queensland research, led by palaeontologist Dr Anthony Romilio, which analysed southern Queensland dinosaur footprint fossils dated to the latter part of the Jurassic Period, between 165 and 151 million-year-ago.

“I’ve always wondered, where were Australia’s big carnivorous dinosaurs?” Dr Romilio said.

“But I think we’ve found them, right here in Queensland.

“The specimens of these gigantic dinosaurs were not fossilised bones, which are the sorts of things that are typically housed at museums.

“Rather, we looked at footprints, which — in Australia — are much more abundant.

“These tracks were made by dinosaurs walking through the swamp-forests that once occupied much of the landscape of what is now southern Queensland.”

Most of the tracks used in the study belong to theropods, the same group of dinosaurs that includes Australovenator, Velociraptor, and their modern-day descendants, birds.

Dr Romilio said these were clearly not bird tracks.

“Most of these footprints are around 50 to 60 centimetres in length, with some of the really huge tracks measuring nearly 80 centimetres,” he said.

“We estimate these tracks were made by large-bodied carnivorous dinosaurs, some of which were up to three metres high at the hips and probably around 10 metres long.

“To put that into perspective, T. rex got to about 3.25 metres at the hips and attained lengths of 12 to 13 metres long, but it didn’t appear until 90 million years after our Queensland giants.

“The Queensland tracks were probably made by giant carnosaurs — the group that includes the Allosaurus.

“At the time, these were probably some of the largest predatory dinosaurs on the planet.”

Despite the study providing important new insights into Australia’s natural heritage, the fossils are not a recent discovery.

“The tracks have been known for more than half a century,” Dr Romilio said.

“They were discovered in the ceilings of underground coal mines from Rosewood near Ipswich, and Oakey just north of Toowoomba, back in the 1950s and 1960s.

“Most hadn’t been scientifically described, and were left for decades in museum drawers waiting to be re-discovered.

“Finding these fossils has been our way of tracking down the creatures from Australia’s Jurassic Park.”


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Ancient crocodiles walked on two legs like dinosaurs

An international research team has been stunned to discover that some species of ancient crocodiles walked on their two hind legs like dinosaurs and measured over three metres in length.

University of Queensland palaeontologist Dr Anthony Romilio said the researchers first thought the similar-shaped fossilised footprints were from another ancient animal known as the pterosaurs.

“At one site, the footprints were initially thought to be made by a giant bipedal pterosaur walking on the mudflat, we now understand that these were bipedal crocodile prints,” Dr Romilio said.

“The footprints measure around 24 centimetres, suggesting the track-makers had legs about the same height as human adult legs.

“These were long animals that we estimate were over three metres in length.

“And while footprints were everywhere on the site, there were no handprints.”

The research team, led by Professor Kyung Soo Kim from Chinju National University of Education, soon found clues as to why there were no handprints.

“Typical crocodiles walk in a squat stance and create trackways that are wide,” Professor Kim said.

“Oddly, our trackways are very narrow looking — more like a crocodile balancing on a tight-rope.

“When combined with the lack of any tail-drag marks, it became clear that these creatures were moving bipedally.

“They were moving in the same way as many dinosaurs, but the footprints were not made by dinosaurs.

“Dinosaurs and their bird descendants walk on their toes.

“Crocodiles walk on the flat of their feet leaving clear heel impressions, like humans do.”

The footprints dated between 110-120 million years ago and were discovered after analysing animal track sites in what is now known as South Korea.

Researchers initially questioned the absence of hand impressions from the trackways, given that today’s typical crocodiles are ‘four-legged’ or quadrupedal.

“Fossil crocodile tracks are quite rare in Asia, so finding an abundance of nearly one hundred footprints was extraordinary,” Dr Romilio said.

“As an animal walks, the hind feet have the potential of stepping into the impression made by the hand and ‘over-printing’ it, but we find no evidence of this at these Korean sites.

“It isn’t due to poor preservation either, because these fossils are spectacular, they even have the fine details of the toe-pads and scales on their soles preserved.”


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Journal Reference:

  1. Kyung Soo Kim, Martin G. Lockley, Jong Deock Lim, Seul Mi Bae, Anthony Romilio. Trackway evidence for large bipedal crocodylomorphs from the Cretaceous of KoreaScientific Reports, 2020; 10 (1) DOI: 10.1038/s41598-020-66008-7

Scientists discover what an armored dinosaur ate for its last meal

More than 110 million years ago, a lumbering 1,300-kilogram, armour-plated dinosaur ate its last meal, died, and was washed out to sea in what is now northern Alberta. This ancient beast then sank onto its thorny back, churning up mud in the seabed that entombed it — until its fossilized body was discovered in a mine near Fort McMurray in 2011.

Since then, researchers at the Royal Tyrrell Museum of Palaeontology in Drumheller, Alta., Brandon University, and the University of Saskatchewan (USask) have been working to unlock the extremely well-preserved nodosaur’s many secrets — including what this large armoured dinosaur (a type of ankylosaur) actually ate for its last meal.

“The finding of the actual preserved stomach contents from a dinosaur is extraordinarily rare, and this stomach recovered from the mummified nodosaur by the museum team is by far the best-preserved dinosaur stomach ever found to date,” said USask geologist Jim Basinger, a member of the team that analyzed the dinosaur’s stomach contents, a distinct mass about the size of a soccer ball.

“When people see this stunning fossil and are told that we know what its last meal was because its stomach was so well preserved inside the skeleton, it will almost bring the beast back to life for them, providing a glimpse of how the animal actually carried out its daily activities, where it lived, and what its preferred food was.”

There has been lots of speculation about what dinosaurs ate, but very little known. In a just-published article in Royal Society Open Science, the team led by Royal Tyrrell Museum palaeontologist Caleb Brown and Brandon University biologist David Greenwood provides detailed and definitive evidence of the diet of large, plant-eating dinosaurs — something that has not been known conclusively for any herbivorous dinosaur until now.

“This new study changes what we know about the diet of large herbivorous dinosaurs,” said Brown. “Our findings are also remarkable for what they can tell us about the animal’s interaction with its environment, details we don’t usually get just from the dinosaur skeleton.”

Previous studies had shown evidence of seeds and twigs in the gut but these studies offered no information as to the kinds of plants that had been eaten. While tooth and jaw shape, plant availability and digestibility have fuelled considerable speculation, the specific plants herbivorous dinosaurs consumed has been largely a mystery.

So what was the last meal of Borealopelta markmitchelli (which means “northern shield” and recognizes Mark Mitchell, the museum technician who spent more than five years carefully exposing the skin and bones of the dinosaur from the fossilized marine rock)?

“The last meal of our dinosaur was mostly fern leaves — 88 per cent chewed leaf material and seven per cent stems and twigs,” said Greenwood, who is also a USask adjunct professor.

“When we examined thin sections of the stomach contents under a microscope, we were shocked to see beautifully preserved and concentrated plant material. In marine rocks we almost never see such superb preservation of leaves, including the microscopic, spore-producing sporangia of ferns.”

Team members Basinger, Greenwood and Brandon University graduate student Jessica Kalyniuk compared the stomach contents with food plants known to be available from the study of fossil leaves from the same period in the region. They found that the dinosaur was a picky eater, choosing to eat particular ferns (leptosporangiate, the largest group of ferns today) over others, and not eating many cycad and conifer leaves common to the Early Cretaceous landscape.

Specifically, the team identified 48 palynomorphs (microfossils like pollen and spores) including moss or liverwort, 26 clubmosses and ferns, 13 gymnosperms (mostly conifers), and two angiosperms (flowering plants).

“Also, there is considerable charcoal in the stomach from burnt plant fragments, indicating that the animal was browsing in a recently burned area and was taking advantage of a recent fire and the flush of ferns that frequently emerges on a burned landscape,” said Greenwood.

“This adaptation to a fire ecology is new information. Like large herbivores alive today such as moose and deer, and elephants in Africa, these nodosaurs by their feeding would have shaped the vegetation on the landscape, possibly maintaining more open areas by their grazing.”

The team also found gastroliths, or gizzard stones, generally swallowed by animals such as herbivorous dinosaurs and today’s birds such as geese to aid digestion.

“We also know that based on how well-preserved both the plant fragments and animal itself are, the animal’s death and burial must have followed shortly after the last meal,” said Brown. “Plants give us a much better idea of season than animals, and they indicate that the last meal and the animal’s death and burial all happened in the late spring to mid-summer.”

“Taken together, these findings enable us to make inferences about the ecology of the animal, including how selective it was in choosing which plants to eat and how it may have exploited forest fire regrowth. It will also assist in understanding of dinosaur digestion and physiology.”

Borealopelta markmitchelli, discovered during mining operations at the Suncor Millennium open pit mine north of Fort McMurray, has been on display at the Royal Tyrrell Museum since 2017. The main chunk of the stomach mass is on display with the skeleton.

Other members of the team include museum scientists Donald Henderson and Dennis Braman, and Brandon University research associate and USask alumna Cathy Greenwood.

Research continues on Borealopelta markmitchelli — the best fossil of a nodosaur ever found — to learn more about its environment and behaviour while it was alive. Student Kalyniuk is currently expanding her work on fossil plants of this age to better understand the composition of the forests in which it lived. Many of the fossils she will examine are in Basinger’ collections at USask.

The research was funded by Canada Foundation for Innovation, Research Manitoba, Natural Sciences and Engineering Research Council of Canada, National Geographic Society, Royal Tyrrell Museum Cooperating Society, and Suncor Canada, as well as in-kind support from Olympus Canada.


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The movie ‘Jurassic Park’ got it wrong: Raptors don’t hunt in packs

A new University of Wisconsin Oshkosh analysis of raptor teeth published in the peer-reviewed journal Palaeogeography, Palaeoclimatology, Palaeoecology shows that Velociraptors and their kin likely did not hunt in big, coordinated packs like dogs.

The raptors (Deinonychus antirrhopus) with their sickle-shaped talons were made famous in the 1993 blockbuster movie Jurassic Park, which portrayed them as highly intelligent, apex predators that worked in groups to hunt large prey.

“Raptorial dinosaurs often are shown as hunting in packs similar to wolves,” said Joseph Frederickson, a vertebrate paleontologist and director of the Weis Earth Science Museum on the UWO Fox Cities campus. “The evidence for this behavior, however, is not altogether convincing. Since we can’t watch these dinosaurs hunt in person, we must use indirect methods to determine their behavior in life.”

Frederickson led the study in partnership with two colleagues at the University of Oklahoma and Sam Noble Museum, Michael Engel and Richard Cifell.

Though widely accepted, evidence for the pack-hunting dinosaur proposed by the late famed Yale University paleontologist John Ostrom is relatively weak, Frederickson said.

“The problem with this idea is that living dinosaurs (birds) and their relatives (crocodilians) do not usually hunt in groups and rarely ever hunt prey larger than themselves,” he explained.

“Further, behavior like pack hunting does not fossilize so we can’t directly test whether the animals actually worked together to hunt prey.”

Recently, scientists have proposed a different model for behavior in raptors that is thought to be more like Komodo dragons or crocodiles, in which individuals may attack the same animal but cooperation is limited.

“We proposed in this study that there is a correlation between pack hunting and the diet of animals as they grow,” Frederickson said.

In Komodo dragons, babies are at risk of being eaten by adults, so they take refuge in trees, where they find a wealth of food unavailable to their larger ground-dwelling parents. Animals that hunt in packs do not generally show this dietary diversity.

“If we can look at the diet of young raptors versus old raptors, we can come up with a hypothesis for whether they hunted in groups,” Frederickson said.

To do this, the scientists considered the chemistry of teeth from the raptor Deinonychus, which lived in North America during the Cretaceous Period about 115 to 108 million years ago.

“Stable isotopes of carbon and oxygen were used to get an idea of diet and water sources for these animals. We also looked at a crocodilian and an herbivorous dinosaur from the same geologic formation,” he said.

The scientists found that the Cretaceous crocodilians, like modern species, show a difference in diet between the smallest and largest teeth, indicating a distinct transition in diet as they grew.

“This is what we would expect for an animal where the parents do not provide food for their young,” Frederickson said. “We also see the same pattern in the raptors, where the smallest teeth and the large teeth do not have the same average carbon isotope values, indicating they were eating different foods. This means the young were not being fed by the adults, which is why we believe Jurassic Park was wrong about raptor behavior.”

Frederickson added that the method used in this study to analyze carbon in teeth could be applied to see whether other extinct creatures may have hunted in packs.


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Journal Reference:

  1. J.A. Frederickson, M.H. Engel, R.L. Cifelli. Ontogenetic dietary shifts in Deinonychus antirrhopus (Theropoda; Dromaeosauridae): Insights into the ecology and social behavior of raptorial dinosaurs through stable isotope analysisPalaeogeography, Palaeoclimatology, Palaeoecology, 2020; 109780 DOI: 10.1016/j.palaeo.2020.109780

Marooned on Mesozoic Madagascar

In evolutionary terms, islands are the stuff of weirdness. It is on islands where animals evolve in isolation, often for millions of years, with different food sources, competitors, predators, and parasites…indeed, different everything compared to mainland species. As a result, they develop into different shapes and sizes and evolve into new species that, given enough time, spawn yet more new species.

Such is the case with the discovery of a new, bizarre 66-million-old mammal in Madagascar by a team of international researchers led by Dr. David Krause, senior curator of vertebrate paleontology at the Denver Museum of Nature & Science and professor emeritus at Stony Brook University, where part of the research was done. The discovery of this opossum-sized mammal that lived among dinosaurs and massive crocodiles on the fourth largest island on Earth was announced today in the journal Nature. Dr. James B. Rossie of Stony Brook University is one of the study’s co-authors. The late Yaoming Hu of Stony Brook University was also a co-author.

The finding of the new mammal, called Adalatherium, which is translated from the Malagasy and Greek languages and means “crazy beast,” is based on a nearly complete skeleton that is astoundingly well preserved. The skeleton is the most complete for any Mesozoic mammal yet discovered in the southern hemisphere.

Krause said that, “knowing what we know about the skeletal anatomy of all living and extinct mammals, it is difficult to imagine that a mammal like Adalatherium could have evolved; it bends and even breaks a lot of rules.”

In fact, although a life-like reconstruction might lead one to think that Adalatherium was a run-of-the-mill badger, its “normality” is literally only skin deep. Below the surface, its skeleton is nothing short of “outlandish.” It has primitive features in its snout region (like a septomaxilla bone) that hadn’t been seen for a hundred million years in the lineage leading to modern mammals.

“Its nasal cavity exhibits an amazing mosaic of features, some of which are very standard for a mammal, but some that I’ve never seen in anything before,” Rossie declared.

Adalatherium had more holes (foramina) on its face than any known mammal, holes that served as passageways for nerves and blood vessels supplying a very sensitive snout that was covered with whiskers. And there is one very large hole on the top of its snout for which there is just no parallel in any known mammal, living or extinct.

The teeth of Adalatherium are vastly different in construction than any known mammal. Its backbone had more vertebrae than any Mesozoic mammal and one of its leg bones was strangely curved.

About the size of a Virginia opossum, Adalatherium was also unusual in that it was very large for its day; most mammals that lived alongside dinosaurs were much smaller, mouse-sized on average.

Adalatherium belongs to an extinct group of mammals called gondwanatherians because they are only known from the ancient southern supercontinent of Gondwana. Gondwanatherian fossils were first found in Argentina in the 1980s but have since also been found in Africa, India, the Antarctic Peninsula, and Madagascar. Gondwanatherians were first thought to be related to modern-day sloths, anteaters, and armadillos but “now are known to have been part of a grand evolutionary experiment, doing their own thing, an experiment that failed and was snuffed out in the Eocene, about 45 million years ago,” Krause explained.

Prior to the discovery of the nearly complete skeleton of Adalatherium, gondwanatherians were only known from isolated teeth and jaw fragments, with the exception of a cranium from Madagascar described by Krause and his team in 2014.

The completeness and excellent preservation of the skeleton of Adalatherium potentially opens up new windows into what gondwanatherians looked like and how they lived, but the bizarre features still have the scientific team guessing.

As Krause’s primary collaborator Simone Hoffmann of the New York Institute of Technology put it, “Adalatherium is the oddest of oddballs. Trying to figure out how it moved is nearly impossible because, for instance, its front end is telling us a different story than its back end.” The research team is still uncovering clues but thinks that, although Adalatherium might have been a powerful digging animal, it was also capable of running and potentially even had other forms of locomotion.

The plate tectonic history of Gondwana provides independent evidence for why Adalatherium is so bizarre. Adalatherium was found in rocks dated to near the end of the Cretaceous, at 66 million years ago. Madagascar, with the Indian subcontinent attached to the east, separated from Africa over a hundred million years before and finally became isolated as an island in the Indian Ocean when the Indian subcontinent detached at approximately 88 million years ago and drifted northward. That left the lineage that ultimately resulted in Adalatherium to evolve, isolated from mainland populations, for over 20 million years — “ample time to develop its many ludicrous features,” said Krause.

The fossil record of early mammals from the northern hemisphere is roughly an order of magnitude better than from the south.

Adalatherium is just one piece, but an important piece, in a very large puzzle on early mammalian evolution in the southern hemisphere,” Krause noted. “Unfortunately, most of the pieces are still missing.”

More than anything, this discovery underscores to the researchers how much more remains to be learned by making new discoveries of early mammals in Madagascar and other parts of the former Gondwana.

In addition to Krause, Hoffmann, and Rossie, other researchers involved in the new discovery — which was funded by the National Science Foundation and National Geographic Society — were: the late Yaoming Hu of Stony Brook University; John R. Wible of Carnegie Museum of Natural History; Guillermo W. Rougier of University of Louisville; E. Christopher Kirk of University of Texas at Austin; Joseph R. Groenke of Stony Brook University and Ohio University; Raymond R. Rogers of Macalester College; Julia A. Schultz of Institut für Geowissenschaften der Universität Bonn, Alistair R. Evans of Monash University and Museums Victoria; Wighart von Koenigswald of Institut für Geowissenschaften der Universität Bonn; and Lydia J. Rahantarisoa of Université d’Antananarivo.

The new Adalatherium mammal is just the latest of a series of bizarre back-boned animals discovered by Krause and his research team on Madagascar over the past 25 years. Earlier discoveries have included a giant, armored, predatory frog (Beelzebufo), a pug-nosed, vegetarian crocodile (Simosuchus), and a small, buck-toothed dinosaur (Masiakasaurus).

The island itself is filled with animals (and plants) found nowhere else on the planet, including hissing cockroaches, giraffe weevils, tomato frogs, Satanic leaf-tailed geckos, panther chameleons, and streaked tenrecs to name a few. And, of course, there is the signature group of mammals — lemurs — made famous in the animated “Madagascar” movies. Only a few thousand years ago, the Madagascar fauna also included 1400-pound elephant birds, gorilla-sized lemurs, and pygmy hippopotamuses.


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Fourth new pterosaur discovery in matter of weeks

You wait ages for a pterosaur and then four come along at once.

Hot on the heels of a recent paper discovering three new species of pterosaur, University of Portsmouth palaeobiologists have identified another new species — the first of its kind to be found on African soil.

Pterosaurs are the less well-known cousins of dinosaurs. They had adept flying ability — some as large as a fighter jet and others as small as a model aeroplane.

The new species belongs to a group of pterosaurs called tapejarids from the Cretaceous period. Tapejarids were small to medium-sized pterosaurs with wingspans perhaps as wide as four metres, most of which had large, broad crests sweeping up from the front of the skull.

They are well known in Brazil and China, and specimens have also been discovered in Europe, but this is the first time the flying reptile has been found in Africa.

It differs from the three recent species discovered as this one had no teeth — it was ‘edentulous’.

Professor David Martill, from the University’s School of the Environment, Geography and Geosciences, led the study. He said: “The study of Moroccan material shows that we are still far from having found all the paleontological treasures of North Africa. Even fragmentary fossils, like the jaw piece of the new pterosaur, can give us important information about the biodiversity of the past.”

PhD student Roy Smith, one of the co-authors, said: “I feel very privileged to be part of such an exciting discovery. Working in the Sahara was a life-changing experience, and discovering a new species of pterosaur is the icing on the cake.”

The new pterosaur has been named Afrotapejara zouhrii to honour the Moroccan palaeontologist Professor Samir Zouhri. Originally a mammal specialist, Zouhri also contributed to several discoveries of prehistoric reptiles in Morocco, including dinosaurs and pterosaurs.

Professor Martill said: “The opportunity to illuminate the diversity of pterosaurs in Africa while honouring a colleague does not happen every day.”

The research team included Dr David Unwin from the University of Leicester and Dr Nizar Ibrahim from the University of Detroit Mercy.

Palaeontologist Dr Ibrahim, said: “Samir Zouhri has played an important role in the development of Moroccan palaeontology, not only through his publications, but also because he organised scientific conferences in Morocco and edited an entire volume for the Geological Society of France on the subject of vertebrate palaeontology in Morocco.”

The fossil material is part of the collections of the Faculty of Sciences Aïn Chock, Casablanca Hassan II University and the paper was published in Cretaceous Research.


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