Tooth Is ‘Smoking Gun’ Evidence That Tyrannosaurus Rex Was Hunter, Killer

July 16, 2013 — Tyrannosaurus rex has long been popular with kids and moviemakers as the most notorious, vicious killing machine to roam the planet during the age of the dinosaurs.

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So, it may come as a shock that for more than a century some paleontologists have argued that T. rex was a scavenger, not a true predator — more like a vulture than a lion. Indeed, a lack of definitive fossil proof of predation in the famous theropod has stirred controversy among scientists — until now.

“T. rex is the monster of our dreams,” said David Burnham, preparator of vertebrate paleontology at the Biodiversity Institute at the University of Kansas. “But ever since it was discovered in Montana and named in the early 1900s, there’s been a debate about whether these large carnivores were scavengers or predators. Most people assume they were predators, but the scientific evidence for predation has been really elusive. Yes, we’ve found lots of dinosaur skeletons with tooth marks that had been chewed up by something. But what did that really prove? Yes, these large carnivores fed on other dinosaurs — but did they eat them while they were alive or dead? That’s where the debate came in. Where was the evidence for hunt and kill?”

Now, Burnham is part of a team that has unearthed “smoking gun” physical proof that T. rex was indeed a predator, hunter and killer. In the Hell Creek Formation of South Dakota, Burnham and colleagues discovered the crown of a T. rex tooth lodged in the fossilized spine of a plant-eating hadrosaur that seems to have survived the attack. The team describes the find in the current issue of the Proceedings of the National Academy of Sciences.

Burnham’s KU co-authors are Bruce Rothschild and the late Larry Martin, along with former KU student Robert DePalma II of The Palm Beach Museum of Natural History and Peter Larson of the Black Hills Institute of Geological Research.

“Robert DePalma was a student here at KU doing his master’s thesis in the Hell Creek formation,” said Burnham. “He found a specimen that represents the tail of one of these hadrosaurs. It had a distorted-looking bone growth. He came to me and said, ‘What do you think is causing this?’ So we cleaned it and could see a tooth embedded in one of these duck-billed dinosaur vertebrae. Then we went to Lawrence Memorial Hospital and used a CT machine to scan the bones — and we saw all of the tooth.”

Previous evidence for predation included T. rex fossil discoveries with preserved stomach contents that included the bones of a young ceratopsian (e.g., Triceratops or one of its kin). However, there was no evidence to conclude whether the ceratopsian was alive or dead when the T. rex made a snack of it.

By contrast, Burnham said the tooth was definitive evidence of hunting, after carefully measuring its length and the size of its serrations to ensure that it came from the mouth of a T. rex.

“Lo and behold, the tooth plotted out just exactly with T. rex — the only known large theropod from the Hell Creek formation,” he said. “We knew we had a T. rex tooth in the tail of a hadrosaur. Better yet, we knew the hadrosaur got away because the bone had begun to heal. Quite possibly it was being pursued by the T. rex when it was bitten. It was going in the right direction — away. The hadrosaur escaped by some stroke of luck. The better luck is finding this fossil with the preserved evidence.”

Because T. rex regularly shed its teeth, the predator went away hungry, but otherwise no worse for the encounter. It would have grown a new tooth to replace the one left behind in the hadrosaur’s tail. This could have been a typical example of T. rex’s hunting efforts, even if it didn’t result in a meal.

“To make an analogy to modern animals, when lions go attack a herd of herbivores, they go after the sick and the slow,” Burnham said. “Most of the time, hadrosaurs traveled in packs. This hadrosaur may have been a little slower, or this T. rex may have been a little faster — at least fast enough to almost catch a duck-billed dinosaur.”

This concrete proof of T. rex’s predation continues a long relationship between KU paleontologists and the theropod, which lived in North America during the Late Cretaceous, some 65 million years ago. KU graduate Barnum Brown discovered the first documented remains of the dinosaur in Wyoming in 1900.

Fossil Saved from Mule Track Revolutionizes Understanding of Ancient Dolphin-Like Marine Reptile

May 14, 2013 — An international team of scientists have revealed a new species of ichthyosaur (a dolphin-like marine reptile from the age of dinosaurs) from Iraq, which revolutionises our understanding of the evolution and extinction of these ancient marine reptiles.
The results, produced by a collaboration of researchers from universities and museums in Belgium and the UK and published today (May 15) in Biology Letters, contradict previous theories that suggest the ichthyosaurs of the Cretaceous period (the span of time between 145 and 66 million years ago) were the last survivors of a group on the decline.

Ichthyosaurs are marine reptiles known from hundreds of fossils from the time of the dinosaurs. “They ranged in size from less than one to over 20 metres in length. All gave birth to live young at sea, and some were fast-swimming, deep-diving animals with enormous eyeballs and a so-called warm-blooded physiology,” says lead author Dr Valentin Fischer of the University of Liege in Belgium.

Until recently, it was thought that ichthyosaurs declined gradually in diversity through multiple extinction events during the Jurassic period. These successive events were thought to have killed off all ichthyosaurs except those strongly adapted for fast-swimming life in the open ocean. Due to this pattern, it has been assumed that ichthyosaurs were constantly and rapidly evolving to be ever-faster open-water swimmers; seemingly, there was no ‘stasis’ in their long evolutionary history.

However, an entirely new ichthyosaur from the Kurdistan region of Iraq substantially alters this view of the group. The specimen concerned was found during the 1950s by British petroleum geologists. “The fossil — a well-preserved partial skeleton that consists of much of the front half of the animal — wasn’t exactly being treated with the respect it deserves. Preserved within a large, flat slab of rock, it was being used as a stepping stone on a mule track,” says co-author Darren Naish of the University of Southampton. “Luckily, the geologists realized its potential importance and took it back to the UK, where it remains today,” adds Dr Naish, who is based at the National Oceanography Centre, Southampton.

Study of the specimen began during the 1970s with ichthyosaur expert Robert Appleby, then of University College, Cardiff. “Robert Appleby recognised that the specimen was significant, but unfortunately died before resolving the precise age of the fossil, which he realised was critical,” says Jeff Liston of National Museums Scotland and manager of the research project. “So continuation of the study fell to a new generation of researchers.”

In the new study (which properly includes Appleby as an author), researchers name it Malawania anachronus, which means ‘out of time swimmer’. Despite being Cretaceous in age, Malawania represents the last-known member of a kind of ichthyosaur long believed to have gone extinct during the Early Jurassic, more than 66 million years earlier. Remarkably, this kind of archaic ichthyosaur appears characterised by an evolutionary stasis: they seem not to have changed much between the Early Jurassic and the Cretaceous, a very rare feat in the evolution of marine reptiles.

“Malawania’s discovery is similar to that of the coelacanth in the 1930s: it represents an animal that seems ‘out of time’ for its age. This ‘living fossil’ of its time demonstrates the existence of a lineage that we had never even imagined. Maybe the existence of such Jurassic-style ichthyosaurs in the Cretaceous has been missed because they always lived in the Middle-East, a region that has previously yielded only a single, very fragmentary ichthyosaur fossil,” adds Dr Fischer.

Thanks to both their study of microscopic spores and pollen preserved on the same slab as Malawania, and to their several analyses of the ichthyosaur family tree, Fischer and his colleagues retraced the evolutionary history of Cretaceous ichthyosaurs. In fact, the team was able to show that numerous ichthyosaur groups that appeared during the Triassic and Jurassic ichthyosaur survived into the Cretaceous. It means that the supposed end of Jurassic extinction event did not ever occur for ichthyosaurs, a fact that makes their fossil record quite different from that of other marine reptile groups.

When viewed together with the discovery of another ichthyosaur by the same team in 2012 and named Acamptonectes densus, the discovery of Malawania constitutes a ‘revolution’ in how we imagine ichthyosaur evolution and extinction. It now seems that ichthyosaurs were still important and diverse during the early part of the Cretaceous. The final extinction of the ichthyosaurs — an event that occurred about 95 million years ago (long before the major meteorite-driven extinction event that ended the Cretaceous) — is now even more confusing than previously assumed.

Oldest? New ‘Bone-Head’ Dinosaur Hints at Higher Diversity of Small Dinosaurs

May 7, 2013 — Scientists have named a new species of bone-headed dinosaur (pachycephalosaur) from Alberta, Canada. Acrotholus audeti (Ack-RHO-tho-LUS) was identified from both recently discovered and historically collected fossils. Approximately six feet long and weighing about 40 kilograms in life, the newly identified plant-eating dinosaur represents the oldest bone-headed dinosaur in North America, and possibly the world.
Dr. Michael Ryan, curator of vertebrate paleontology at The Cleveland Museum of Natural History, co-authored research describing the new species, which was published May 7, 2013 in the journal Nature Communications.

Acrotholus means “high dome,” referring to its dome-shaped skull, which is composed of solid bone over 10 centimeters (two inches) thick. The name Acrotholus audeti also honors Alberta rancher Roy Audet, on whose land the best specimen was discovered in 2008. Acrotholus walked on two legs and had a greatly thickened, domed skull above its eyes, which was used for display to other members of its species, and may have also been used in head-butting contests. Acrotholus lived about 85 million years ago.

The new dinosaur discovery is based on two skull ‘caps’ from the Milk River Formation of southern Alberta. One of these was collected by the Royal Ontario Museum (ROM) more than 50 years ago. However, a better specimen was found in 2008 by University of Toronto graduate student Caleb Brown during a field expedition organized by Dr. David Evans of the Royal Ontario Museum and University of Toronto, and Ryan.

“Acrotholus provides a wealth of new information on the evolution of bone-headed dinosaurs. Although it is one of the earliest known members this group, its thickened skull dome is surprisingly well-developed for its geological age,” said lead author Evans, ROM curator, vertebrate palaeontology. “More importantly, the unique fossil record of these animals suggests that we are only beginning to understand the diversity of small-bodied plant-eating dinosaurs.”

Small mammals and reptiles can be very diverse and abundant in modern ecosystems, but small dinosaurs (less than 100 kg) are considerably less common than large ones in the fossil record. Whether this pattern is a true reflection of dinosaur communities, or is related to the greater potential for small bones to be destroyed by carnivores and natural decay, has been debated. The massively constructed skull domes of pachycephalosaurs are resistant to destruction, and are much more common than their relatively delicate skeletons — which resemble those of other small plant-eating dinosaurs. Therefore, the researchers suggest that the pachycephalosaur fossil record can provide valuable insights into the diversity of small, plant-eating dinosaurs as a whole.

“We can predict that many new small dinosaur species like Acrotholus are waiting to be discovered by researchers willing to sort through the many small bones that they pick up in the field,” said co-author Ryan of The Cleveland Museum of Natural History. “This fully domed and mature individual suggests that there is an undiscovered, hidden diversity of small-bodied dinosaurs. So when we look back, we need to reimagine the paleoenvironment. There is an evolutionary history that we just don’t know because the fossil record is incomplete. This discovery also highlights the importance of landowners, like Roy Audet, who grant access to their land and allow scientifically important finds to be made.”

This dinosaur is the latest in a series of new finds being made by Evans and Ryan as part of their Southern Alberta Dinosaur Project, which aims to fill in gaps in of the record of Late Cretaceous dinosaurs and study their evolution. This project focuses on the palaeontology of some of the oldest dinosaur-bearing rocks in Alberta, which have been studied less intensely than those of the famous badlands of Dinosaur Provincial Park and Drumheller.

Acrotholus was identified by a team comprising of palaeontologists Evans, of the Royal Ontario Museum; and Ryan, of The Cleveland Museum of Natural History; as well as Ryan Schott, Caleb Brown, and Derek Larson, all graduate students at the University of Toronto who studied under Evans.

New Dinosaur Species: First Fossil Evidence Shows Small Crocs Fed On Baby Dinosaurs

Feb. 28, 2013 — A South Dakota School of Mines & Technology assistant professor and his team have discovered a new species of herbivorous dinosaur and today published the first fossil evidence of prehistoric crocodyliforms feeding on small dinosaurs.

Research by Clint Boyd, Ph.D., provides the first definitive evidence that plant-eating baby ornithopod dinosaurs were a food of choice for the crocodyliform, a now extinct relative of the crocodile family. While conducting their research, the team also discovered that this dinosaur prey was a previously unrecognized species of a small ornithopod dinosaur, which has yet to be named.

The evidence found in what is now known as the Grand Staircase Escalante-National Monument in southern Utah dates back to the late Cretaceous period, toward the end of the age of dinosaurs, and was published today in the online journal PLOS ONE. The complete research findings of Boyd and Stephanie K. Drumheller, of the University of Iowa and the University of Tennessee, and Terry A. Gates, of North Carolina State University and the Natural History Museum of Utah, can be accessed online (see journal reference below).

A large number of mostly tiny bits of dinosaur bones were recovered in groups at four locations within the Utah park — which paleontologists and geologists know as the Upper Cretaceous (Campanian) Kaiparowits Formation — leading paleontologists to believe that crocodyliforms had fed on baby dinosaurs 1-2 meters in total length.

Evidence shows bite marks on bone joints, as well as breakthrough proof of a crocodyliform tooth still embedded in a dinosaur femur.

The findings are significant because historically dinosaurs have been depicted as the dominant species. “The traditional ideas you see in popular literature are that when little baby dinosaurs are either coming out of a nesting grounds or out somewhere on their own, they are normally having to worry about the theropod dinosaurs, the things like raptors or, on bigger scales, the T. rex. So this kind of adds a new dimension,” Boyd said. “You had your dominant riverine carnivores, the crocodyliforms, attacking these herbivores as well, so they kind of had it coming from all sides.”

Based on teeth marks left on bones and the large amounts of fragments left behind, it is believed the crocodyliforms were also diminutive in size, perhaps no more than 2 meters long. A larger species of crocodyliform would have been more likely to gulp down its prey without leaving behind traces of “busted up” bone fragments.

Until now, paleontologists had direct evidence only of “very large crocodyliforms” interacting with “very large dinosaurs.”

“It’s not often that you get events from the fossil record that are action-related,” Boyd explained. “While you generally assume there was probably a lot more interaction going on, we didn’t have any of that preserved in the fossil record yet. This is the first time that we have definitive evidence that you had this kind of partitioning, of your smaller crocodyliforms attacking the smaller herbivorous dinosaurs,” he said, adding that this is only the second published instance of a crocodyliform tooth embedded in any prey animal in the fossil record.

“A lot of times you find material in close association or you can find some feeding marks or traces on the outside of the bone and you can hypothesize that maybe it was a certain animal doing this, but this was only the second time we have really good definitive evidence of a crocodyliform feeding on a prey animal and in this case an ornithischian dinosaur,” Boyd said.

The high concentrations of tiny dinosaur bones led researchers to conclude a type of selection occurred, that crocodyliforms were preferentially feeding on these miniature dinosaurs. “Maybe it was closer to a nesting ground where baby dinosaurs would have been more abundant, and so the smaller crocodyliforms were hanging out there getting a lunch,” Boyd added.

“When we started looking at all the other bones, we starting finding marks that are known to be diagnostic for crocodyliform feeding traces, so all that evidence coming together suddenly started to make sense as to why we were not finding good complete specimens of these little ornithischian dinosaurs,” Boyd explained. “Most of the bites marks are concentrated around the joints, which is where the crocodyliform would tend to bite, and then, when they do their pulling or the death roll that they tend to do, the ends of the bones tend to snap off more often than not in those actions. That’s why we were finding these fragmentary bones.”

In the process of their research, the team discovered through diagnostic cranial material that these baby prey are a new, as yet-to-be-named dinosaur species. Details on this new species will soon be published in another paper.

New Kind of Extinct Flying Reptile Discovered

Feb. 4, 2013 — A new kind of pterosaur, a flying reptile from the time of the dinosaurs, has been identified by scientists from the Transylvanian Museum Society in Romania, the University of Southampton in the UK and the Museau Nacional in Rio de Janiero, Brazil.

The fossilised bones come from the Late Cretaceous rocks of Sebeş-Glod in the Transylvanian Basin, Romania, which are approximately 68 million years old. The Transylvanian Basin is world-famous for its many Late Cretaceous fossils, including dinosaurs of many kinds, as well as fossilised mammals, turtles, lizards and ancient relatives of crocodiles.

A paper on the new species, named Eurazhdarcho langendorfensis has been published in the online journal PLoS ONE. Dr Darren Naish, from the University of Southampton’s Vertebrate Palaeontology Research Group, who helped identify the new species, says: “Eurazhdarcho belong to a group of pterosaurs called the azhdarchids. These were long-necked, long-beaked pterosaurs whose wings were strongly adapted for a soaring lifestyle. Several features of their wing and hind limb bones show that they could fold their wings up and walk on all fours when needed.

“With a three-metre wingspan, Eurazhdarcho would have been large, but not gigantic. This is true of many of the animals so far discovered in Romania; they were often unusually small compared to their relatives elsewhere.”

The discovery is the most complete example of an azhdarchid found in Europe so far and its discovery supports a long-argued theory about the behaviour of these types of creatures.

Dr Gareth Dyke, Senior Lecturer in Vertebrate Palaeontology, based at the National Oceanography Centre Southampton says: “Experts have argued for years over the lifestyle and behaviour of azhdarchids. It has been suggested that they grabbed prey from the water while in flight, that they patrolled wetlands and hunted in a heron or stork-like fashion, or that they were like gigantic sandpipers, hunting by pushing their long bills into mud.

“One of the newest ideas is that azhdarchids walked through forests, plains and other places in search of small animal prey. Eurazhdarcho supports this view of azhdarchids, since these fossils come from an inland, continental environment where there were forests and plains as well as large, meandering rivers and swampy regions.”

Fossils from the region show that there were several places where both giant azhdarchids and small azhdarchids lived side by side. Eurazhdarcho’s discovery indicates that there were many different animals hunting different prey in the region at the same time, demonstrating a much more complicated picture of the Late Cretaceous world than first thought.

Brain of Ampelosaur from Cuenca (Spain) Revealed

Jan. 23, 2013 — Scientists have made a 3D reconstruction of the remains of ampelosaur, found in 2007 in the site of Lo Hueco (Cuenca). The fossils are about 70 million years old (Late Cretaceous).

Up to now, only one species of the genus was known, Ampelosaurus atacis, which was discovered in France. The differences between the Spanish and the French fossils do not rule out that they could represent distinct species.

The researcher from the National Museum of Natural Sciences (CSIC) Fabien Knoll, who has conducted the investigation, considers that “more fossils are necessary to establish that we are dealing with a new species.” For this reason, the team has identified the specimen as Ampelosaurus sp., which leaves open its specific identity.

Little evolved brain

The ampelosaur pertains to the sauropod group, large-sized dinosaurs that settled widely during the Mesozoic Era (which began 253 million years ago and ended 66 million years ago). More precisely, it is a titanosaur, a group of plant eating animals that were dominant during the last half of the Cretaceous (last period of the Mesozoic). The first sauropods appeared about 160 million years earlier than the ampelosaur.

However, despite being the product of a long evolution, the brain of the ampelosaur does not show any notable development. Knoll explains: “This saurian may have reached 15 m in length; nonetheless its brain was not in excess of 8 cm.” According to the CSIC researcher: “Increase in brain size was not favored in the course of sauropod evolution.”

Another of the characteristics yielded by the reconstruction of the Cuenca ampelosaur brain is the small size of the inner ear. According to Knoll: “This may suggest that the ampelosaur would not have been adapted to quickly move either its eyes or its head and neck.”

In January of 2012, Knoll conducted the investigation that led to the reconstruction of another sauropod, Spinophorosaurus nigeriensis. The simulation in 3D of its brain revealed that that species, in contrast to what the study of the ampelosaur braincase demonstrated, presented a fairly well-developed inner ear.

According to the one of the researchers, “It is quite enigmatic that sauropods show such a diverse inner ear morphology whereas they have a very homogenous body shape; more investigation is definitely required.”

New Study Sheds Light On Dinosaur Size

Dec. 19, 2012 — Dinosaurs were not only the largest animals to roam the Earth — they also had a greater number of larger species compared to all other back-boned animals — scientists suggest in a new paper published in the journal PLOS ONE.

The researchers, from Queen Mary, University of London, compared the size of the femur bone of 329 different dinosaur species from fossil records. The length and weight of the femur bone is a recognised method in palaeontology for estimating a dinosaur’s body mass.
They found that dinosaurs follow the opposite pattern of body size distribution as seen in other vertebrate species. For example, within living mammals there tends to be few larger species, such as elephants, compared to smaller animals, such as mice, which have many species. The evidence from fossil records implies that in contrast there were many species of larger dinosaurs and few small species.
Dr David Hone from Queen Mary’s School of Biological and Chemical Sciences, explains: “What is remarkable is that this tendency to have more species at a bigger size seemed to evolve quite early on in dinosaurian evolution around the Late Triassic period, 225 million years ago, raising questions about why they got to be so big.
“Our evidence supports the hypothesis that young dinosaurs occupied a different ecological niche to their parents so they weren’t in competition for the same sources of food as they ate smaller plants or preyed on smaller size animals. In fact, we see modern crocodiles following this pattern — baby crocodiles start by feeding off insects and tadpoles before graduating onto fish and then larger mammals.”
Dr Eoin Gorman, also from Queen Mary’s School of Biological and Chemical Sciences added: “There is growing evidence that dinosaurs produced a large number of offspring, which were immediately vulnerable to predation due to their smaller size. It was beneficial for the herbivores to grow to large size as rapidly as possible to escape this threat, but the carnivores had sufficient resources to live optimally at smaller sizes.
“These differences are reflected in our analyses and also offer an explanation why other groups do not follow a similar pattern. Several modern-day vertebrate groups are almost entirely carnivorous, while many of the herbivores are warm-blooded, which limits their size.”

New Dinosaur: First Freshwater Mosasaur Discovered

Dec. 19, 2012 — A new mosasaur species discovered in Hungary is the first known example of this group of scaled reptiles to have lived in freshwater river environments similar to modern freshwater dolphins.
The research is published Dec. 19 in the open-access journal PLOS ONE by Laszlo Makadi from the Hungarian Natural History Museum, Hungary and colleagues from the University of Alberta, Canada and MTA-ELTE Lendület Dinosaur Research Group, Hungary.
The species lived about 84 million years ago, the largest specimens reached about 20 feet in length, and belongs to a family called ‘mosasaurs’, conventionally thought of as gigantic finned marine lizards, similar and perhaps even related to present day monitor lizards. The researchers discovered several fossils of the new species, ranging from small juveniles to large adults that suggest that this species had limbs like a terrestrial lizard, a flattened, crocodile-like skull, and a tail unlike other known members of the mosasaur family.
The fossils were recovered from an open-pit mine in the Bakony Hills of Western Hungary, which were once flood-plains. According to the study, this is the first known mosasaur that lived in freshwater, and only the second specimen of a mosasaur to have been found in rocks that were not once deposited in the ocean. Makadi says, “The evidence we provide here makes it clear that similar to some lineages of cetaceans, mosasaurs quickly adapted to a variety of aquatic environments, with some groups re- invading available niches in freshwater habitats. The size of Pannoniasaurus makes it the largest known predator in the waters of this paleo-environment.”
Even in the modern world, scaly reptiles in the aquatic world are extremely rare. Only a few species live in the water, and even fewer, like marine iguanas and sea kraits, live in the oceans. The new species described here probably adapted to freshwater environments similarly to river dolphins, such as those now inhabiting the Amazon, Ganges and Yangtze rivers.

Were Dinosaurs Undergoing Long-Term Decline Before Mass Extinction?

ScienceDaily (May 1, 2012) — Despite years of intensive research about the extinction of non-avian dinosaurs about 65.5 million years ago, a fundamental question remains: were dinosaurs already undergoing a long-term decline before an asteroid hit at the end of the Cretaceous? A study led by scientists at the American Museum of Natural History gives a multifaceted answer.
The findings, published online May 1 in Nature Communications, suggest that in general, large-bodied, “bulk-feeding” herbivores were declining during the last 12 million years of the Cretaceous. But carnivorous dinosaurs and mid-sized herbivores were not. In some cases, geographic location might have been a factor in the animals’ biological success.

“Few issues in the history of paleontology have fueled as much research and popular fascination as the extinction of non-avian dinosaurs,” said lead author Steve Brusatte, a Columbia University graduate student affiliated with the Museum’s Division of Paleontology. “Did sudden volcanic eruptions or an asteroid impact strike down dinosaurs during their prime? We found that it was probably much more complex than that, and maybe not the sudden catastrophe that is often portrayed.”

The research team, which includes Brusatte; Mark Norell, chair of the Museum’s Division of Paleontology; and scientists Richard Butler of Ludwig Maximilian University of Munich and Albert Prieto-M‡rquez from the Bavarian State Collection for Palaeontology, both in Germany, is the first to look at dinosaur extinction based on “morphological disparity”-the variability of body structure within particular groups of dinosaurs. Previous research was based almost exclusively on estimates of changes in the number of dinosaur species over time. However, it can be very difficult to do this accurately.

“By looking just at trends in taxonomic diversity, you get conflicting answers about the state of dinosaurs prior to extinction,” Brusatte said. “This is because the results can be biased by uneven sampling of the fossil record. In places where more rock and fossils were formed, like in America’s Great Plains, you’ll find more species. We wanted to go beyond a simple species count for this study.”

By looking at the change in biodiversity within a given dinosaur group over time, researchers can create a rough snapshot of the animals’ overall well-being. This is because groups that show an increase in variability might have been evolving into more species, giving them an ecological edge. On the other hand, decreasing variability might be a warning sign of extinction in the long term.

The researchers calculated morphological disparity for seven major dinosaur groups using databases that include wide-ranging characteristics about the intricate skeletal structure of nearly 150 different species.

“People often think of dinosaurs as being monolithic-we say ‘The dinosaurs did this, and the dinosaurs did that,'” Butler said. “But dinosaurs were hugely diverse. There were hundreds of species living in the Late Cretaceous, and these differed enormously in diet, shape, and size. Different groups were probably evolving in different ways and the results of our study show that very clearly.”

The researchers found that hadrosaurs and ceratopsids, two groups of large-bodied, bulk-feeding herbivores-animals that did not feed selectively-may have experienced a decline in biodiversity in the 12 million years before the dinosaurs ultimately went extinct. In contrast, small herbivores (ankylosaurs and pachycephalosaurs), carnivorous dinosaurs (tyrannosaurs and coelurosaurs), and enormous herbivores without advanced chewing abilities (sauropods) remained relatively stable or even slightly increased in biodiversity.

As a complication, hadrosaurs showed different levels of disparity in different locations. While declining in North America, the disparity of this dinosaur group seems to have been increasing in Asia during the latest Cretaceous.

“These disparity calculations paint a more nuanced picture of the final 12 million years of dinosaur history,” Brusatte said. “Contrary to how things are often perceived, the Late Cretaceous wasn’t a static ‘lost world’ that was violently interrupted by an asteroid impact. Some dinosaurs were undergoing dramatic changes during this time, and the large herbivores seem to have been mired in a long-term decline, at least in North America.”

In North America, extreme fluctuations of the inland Western Interior Sea and mountain building might have affected the evolution of dinosaurs in distinct ways from species on other continents. Therefore, the authors say, the North American record might not be representative of a global pattern, if one exists. They also note that there is no way to tell whether a declining dinosaur group would have survived if the asteroid had not struck Earth.

“Even if the disparity of some dinosaur clades or regional faunas were in decline, this does not automatically mean that dinosaurs were doomed to extinction,” Norell said. “Dinosaur diversity fluctuated throughout the Mesozoic, and small increases or decreases between two or three time intervals may not be noteworthy within the context of the entire 150-million-year history of the group.”

Funding for this study was provided by the National Science Foundation through the Division of Earth Sciences, the Division of Biological Infrastructure, a Graduate Research Fellowship, and a Doctoral Dissertation Improvement Grant; the German Research Foundation’s Emmy Noether Programme; the Alexander von Humboldt Foundation; the Charlotte and Walter Kohler Charitable Trust; the American Museum of Natural History; and Columbia University.

Two New Species of Horned Dinosaur Named

ScienceDaily (Mar. 12, 2012) — Two new horned dinosaurs have been named based on fossils collected from Alberta, Canada. The new species, Unescopceratops koppelhusae and Gryphoceratops morrisoni, are from the Leptoceratopsidae family of horned dinosaurs. The herbivores lived during the Late Cretaceous period between 75 to 83 million years ago. The specimens are described in research published in the Jan. 24, 2012, online issue of the journal Cretaceous Research.

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“These dinosaurs fill important gaps in the evolutionary history of small-bodied horned dinosaurs that lack the large horns and frills of relatives like Triceratops from North America,” said Michael Ryan, Ph.D., curator of vertebrate paleontology at The Cleveland Museum of Natural History, lead author on the research. “Although horned dinosaurs originated in Asia, our analysis suggests that leptoceratopsids radiated to North America and diversified here, since the new species, Gryphoceratops, is the earliest record of the group on this continent.”

Unescoceratops koppelhusae lived approximately 75 million years ago. It measured about one to two meters (6.5 feet) in length and weighed less than 91 kilograms (200 pounds). It had a short frill extending from behind its head but did not have ornamentation on its skull. It had a parrot-like beak. Its teeth were lower and rounder than those of any other leptoceratopsid. In addition, its hatchet-shaped jaw had a distinct portion of bone that projected below the jaw like a small chin.

The lower left jaw fragment of Unescoceratops was discovered in 1995 in Dinosaur Provincial Park, a United Nations Educational, Scientific and Cultural Organization (UNESCO) World Heritage Site by Philip Currie, Ph.D., now of the University of Alberta. Originally described in 1998 by Ryan and Currie, the dinosaur was referred to as Leptoceratops. Subsequent research by Ryan and David Evans, Ph.D., of the Royal Ontario Museum in Toronto, Canada, determined the specimen was a new genus and species. The genus is named to honor the UNESCO World Heritage Site designation for the locality where the specimen was found and from the Greek “ceratops,” which means “horned face.” The species is named for Eva Koppelhus, Ph.D., a palynologist at the University of Alberta and wife of Currie.

Gryphoceratops morrisoni lived about 83 million years ago. It had a shorter and deeper jaw shape than any other leptoceratopsid. Researchers believe the individual was a full-grown adult. Based on unique characteristics of the jaw and its size, the researchers believe that Gryphoceratops was an adult that did not exceed one-half meter in length. This means it is the smallest adult-sized horned dinosaur in North America and one of the smallest adult-sized plant-eating dinosaurs known.

Lower right jaw fragments of Gryphoceratops were discovered in southern Alberta in 1950 by Levi Sternberg while he worked for the Royal Ontario Museum. The genus is named for “Gryphon,” a mythological Greek figure with the body of a lion and the head of an eagle, which is a reference to the animal’s beaked face. The species name honors Ian Morrison, a Royal Ontario Museum technician, who discovered how the bones fit together.

Second author Evans, associate curator of vertebrate palaeontology at the Royal Ontario Museum and assistant professor at the University of Toronto, said, “Small-bodied dinosaurs are typically poorly represented in the fossil record, which is why fragmentary remains like these new leptoceratopsids can make a big contribution to our understanding of dinosaur ecology and evolution.”

Contributing authors are Philip Currie, Ph.D., of the University of Alberta; Caleb Brown of the University of Toronto; and Don Brinkman, Ph.D., of the Royal Tyrrell Museum of Palaeontology.