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Evolution of Dinosaur Skin and Feathers: A Complex Story

June 2, 2015

Today, Paul Barrett from the Natural History Museum, Nicolas Campione, a lab alumnus and researcher at Uppsala University, and I published a detailed study of the evolution of dinosaurian integument. Despite extensive recent speculation, our analyses suggest that the majority of non-avian dinosaurs were more likely to have scales than to exhibit ‘feather-like’ structures that are the direct precursors to the feathers we see in modern birds.

Over the past two decades, a number of spectacularly preserved dinosaur fossils with feathers have revolutionized the field of palaeontology. The presence of feathers in birds and their immediate dinosaurian ancestors – theropods like Velociraptor – is uncontroversial, but the presence of true feather homologues, or protofeathers, in other major groups, such as ornithischian dinosaurs, has been highly debated. Several recent discoveries have suggested that, along with scales, filament-like ‘protofeathers’ might have been present in the common ancestor of all dinosaurs and ubiquitous in the entire group.

In order to test the idea that dinosaurs were primitively feathered,  we compiled a comprehensive database of dinosaur skin fossils- the most complete to date- and attempted to reconstruct the evolutionary history of dinosaur scales and feathers using a maximum likelihood approach. Most of our analyses provide no support for the appearance of feathers in the majority of non-avian dinosaurs, and although many meat-eating dinosaurs were feathered, the ancestor of all dinosaurs was probably scaly. Interestingly, the quills and filaments in some major plant-eating ornithischian dinosaur groups were evolutionary experiments that were independent of true feather origins.

Fossilized impression of the scaly skin of the sauropod dinosaur Barosaurus lentus.

Fossilized impression of the scaly skin of the sauropod dinosaur Barosaurus lentus.

Untangling when particular integumentary features first evolved will help us understand the origins of feathers and why they first arose, but our analyses are limited to the data we have at hand and questions still remain. Importantly, our research also quantifies taphonomic biases and identifies gaps in the fossil record of dinosaur skin. The biggest and most significant gap is in the Triassic and Early Jurassic, when dinosaurs first originated and diversified, where very few integument fossils are known. Rocks of this age also lack significant lake/lagoonal fossil sites where delicate feather-like structures are preferentially preserved. This makes the origin of the direct filamentous precursors to feathers difficult to pinpoint. Whether or not the first dinosaurs had true ‘protofeathers’ may only be finally resolved with the discovery of more fossils, particularly from early in dinosaur evolutionary history.

Reference:

P. M. Barrett, D. C. Evans, and N. E. Campione. 2015.  Evolution of dinosaur epidermal structures. Biology Letters. 20150229. Doi: http://dx.doi.org/10.1098/rsbl.2015.0229

Press Release:

Origins of feathered dinosaurs more complex than first thought

Media:

Feathers or scales? New research highlights dinosaur diversity

Most dinosaurs had scales, not feathers, fossil analysis concludes

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Dino Hunt Canada Series Airs on HISTORY Canda

February 28, 2015

DinoHunt CanadaIn the last century, nearly 1,000 dinosaur skeletons have been found in Canada, with more being discovered every year. Canada is one of the best places in the world to trace the evolutionary story of dinosaurs – from their first steps to the peak of their diversity and to their ultimate extinction. Through an exciting multi-platform experience, HISTORY travels coast-to-coast with Canada’s top palaeontologists to uncover how dinosaurs lived – and died – right here at home. Dino Hunt Canada is a new 4-part documentary series that tells the story of six teams of Canadian fossil hunters who discover some of the most important dinosaur finds in the world.  Their expeditions take viewers to some of the most stunning locations in Canada, from the red sandstones of Nova Scotia’s Bay of Fundy to the moonscape of the Canadian Badlands in Alberta.

The Dino Hunt Canada digital experience (www.dinohunt.ca) provides Canadians with a fun and engaging, cross-platform glimpse into the discovery of a new dinosaur. You can follow its complete journey beginning with the discovery of the fossils in Alberta, through scientific study and restoration via a live-streaming online feed running directly from the ROM’s Dino Lab, all the way to its eventual reconstruction and public display. The website also offers users the opportunity to Ask an Expert – one-on-one access to the palaeontologists and experts from the miniseries, and learn more about Canada’s rich dinosaur history through the Dino Index’s 3D dino models with added images and encyclopedic text. Through the online “Name Our Dino”contest, Canadians nicknamed the new skeleton “Cornelius”.

DinoHuntWeb

To learn more about Canada’s amazing dinosaur heritage, visit http://www.DinoHunt.ca.

The first episode, features my team from the Royal Ontario Museum (ROM) as we search for the skull bones of what turns out to be a previously unknown horned dinosaur. The newly discovered dinosaur is on display in the New Dino Discovered exhibition, which opened  to the public during the ROM’s Dinos Invade! Big Weekend on January 24 and 25. The exhibition features a cast of the new species, as well as information that takes visitors into the field with us as we dig up the fossils.

Canada's newest dinosaur, a yet-to-be named ceratopsian, on display in the New Dino Discovered exhibit at the Royal Ontario Museum

Canada’s newest dinosaur, a yet-to-be named ceratopsian, on display in the New Dino Discovered exhibit at the Royal Ontario Museum

Hear an interview about the new dinosaur discovery here.

To learn more about Canada’s amazing dinosaur heritage, visit www.DinoHunt.ca.

Introducing Mercuriceratops

June 18, 2014

New Horned Dinosaur Reveals Unique Wing-Shaped Headgear

Today, we annnouce the discovery of  a new species of horned dinosaur (ceratopsian) based on fossils collected from Montana in the United States and Alberta, Canada. Mercuriceratops (mer-cure-E-sare-ah-tops) gemini was approximately 6 meters (20 feet) long and weighed more than 2 tons. It lived about 77 million years ago during the Late Cretaceous Period. Research describing the new species is published online in the journal Naturwissenschaften.

Mercuriceratops (middle) compared to a typical centrosaurine (left) and chamosaurine (right). Courtesy Danielle Dufault.jpg

Mercuriceratops (middle) compared to a typical centrosaurine (left) and chasmosaurine (right). Courtesy Danielle Dufault.

Mercuriceratops (Mercuri + ceratops) means “Mercury horned-face,” referring to the wing-like ornamentation on its head that resembles the wings on the helmet of the Roman god, Mercury. The name “gemini” refers to the almost identical twin specimens found in north central Montana and the UNESCO World Heritage Site, Dinosaur Provincial Park, in Alberta, Canada. Mercuriceratops had a parrot-like beak and probably had two long brow horns above its eyes. It was a plant-eating dinosaur.

Mercuriceratops took a unique evolutionary path that shaped the large frill on the back of its skull into protruding wings like the decorative fins on classic 1950s cars. It definitively would have stood out from the herd during the Late Cretaceous,” said lead author Dr. Michael Ryan, curator of vertebrate paleontology at The Cleveland Museum of Natural History. “Horned dinosaurs in North America used their elaborate skull ornamentation to identify each other and to attract mates—not just for protection from predators. The wing-like protrusions on the sides of its frill may have offered male Mercuriceratops a competitive advantage in attracting mates.”

“The butterfly-shaped frill, or neck shield, of Mercuriceratops is unlike anything we have seen before,” said co-author Dr. David Evans, curator of vertebrate palaeontology at the Royal Ontario Museum. “Mercuriceratops shows that evolution gave rise to much greater variation in horned dinosaur headgear than we had previously suspected.”

The new dinosaur is described from skull fragments from two individuals collected from the Judith River Formation of Montana and the Dinosaur Park Formation of Alberta. The Montana specimen was originally collected on private land and acquired by the Royal Ontario Museum. The Alberta specimen was collected by Susan Owen-Kagen, a preparator in Dr. Philip Currie’s lab at the University of Alberta. “Susan showed me her specimen during one of my trips to Alberta,” said Ryan. “When I saw it my jaw dropped open as I instantly recognized it as being from the same type of dinosaur that the Royal Ontario Museum had from Montana.”

The holotype squamosal of Mercuriceratops from Montana (left) and the referred specimen from Alberta (right)

The holotype squamosal of Mercuriceratops from Montana (left) and the referred specimen from Alberta (right)

The Alberta specimen confirmed that the fossil from Montana was not a pathological specimen, nor had it somehow been distorted during the process of fossilization,” said Dr. Philip Currie, professor and Canada research chair in dinosaur paleobiology at the University of Alberta. “The two fossils—squamosal bones from the side of the frill—have all the features you would expect, just presented in a unique shape.”

This dinosaur is just the latest in a series of new finds being made by Ryan and Evans as part of their Southern Alberta Dinosaur Project, which is designed to fill in gaps in our knowledge of Late Cretaceous dinosaurs and study their evolution. This project focuses on the paleontology of some of oldest dinosaur-bearing rocks in Alberta and the neighbouring rocks of northern Montana that are of the same age.

Body Mass Evolution and Adpative Radiation in Dinosaurs

May 6, 2014

Today we announced the results of a major study on dinosaur body size evolution in a new paper published in PLoS Biology.

From the Press Release: An international, led by scientists at Oxford University and the Royal Ontario Museum, estimated the body mass of 426 dinosaur species based on the thickness of their leg bones. The team found that dinosaurs showed rapid rates of body size evolution shortly after their origins, around 230 million years ago. However, these soon slowed: only the evolutionary line leading to birds continued to change size at this rate, and continued to do so for 170 million years, producing new ecological diversity not seen in other dinosaurs.

Dinosaurs evolved into a huge range of shapes and sizes over 170 million years. Courtesy of Julius Csotonyi.

Dinosaurs evolved into a huge range of shapes and sizes over 170 million years. Courtesy of Julius Csotonyi.

“Dinosaurs aren’t extinct; there are about 10,000 species alive today in the form of birds. We wanted to understand the evolutionary links between this exceptional living group and their Mesozoic relatives, including well-known extinct species like T. rex, Triceratops, and Stegosaurus,” said Dr Roger Benson of Oxford University’s Department of Earth Sciences, who led the study. “We found exceptional body mass variation in the dinosaur line leading to birds, especially in the feathered dinosaurs called maniraptorans. These include Jurassic Park’s Velociraptor, birds, and a huge range of other forms, weighing anything from 15 grams to 3 tonnes, and eating meat, plants, and more omnivorous diets.”

The team believes that small body size might have been key to maintaining evolutionary potential in birds, which broke the lower body size limit of around 1 kilogram seen in other dinosaurs.

“How do you weigh a dinosaur? You can do it by measuring the thickness of its leg bones, like the femur. This is quite reliable,” said Dr Nicolás Campione, of the Uppsala University, a member of the team. “This shows that the biggest dinosaur Argentinosaurus, at 90 tonnes, was 6 million times the weight of the smallest Mesozoic dinosaur, a sparrow-sized bird called Qiliania, weighing 15 grams. Clearly, the dinosaur body plan was extremely versatile.”

The team examined rates of body size evolution on the entire family tree of dinosaurs, sampled throughout their first 170 million years on Earth. If close relatives are fairly similar in size, then evolution was probably quite slow. But if they are very different in size, then evolution must have been fast.

“What we found was striking. Dinosaur body size evolved very rapidly in early forms, likely associated with the invasion of new ecological niches. In general, rates slowed down as these lineages continued to diversify,” said Dr David Evans at the Royal Ontario Museum, who co-devised the project. “But it’s the sustained high rates of evolution in the feathered maniraptoran dinosaur lineage that led to birds – the second great evolutionary radiation of dinosaurs.”

The evolutionary line leading to birds kept experimenting with different, often radically smaller, body sizes – enabling new body ‘designs’ and adaptations to arise more rapidly than among larger dinosaurs. Other dinosaur groups failed to do this, got locked in to narrow ecological niches, and ultimately went extinct. This suggest that important living groups such as birds might result from sustained, rapid evolutionary rates over timescales of hundreds of millions of years, which could not be observed without fossils.

Open-Access Article:

Benson R. B. J., N. E. Campione, M. T. Carrano, P. D. Mannion, C. Sullivan, P. Upchurch, and D. C. Evans. 2014. Rates of dinosaur body mass evolution indicate 170 million years of sustained ecological innovation on the avian stem lineage, PLOS Biology 12(5): e1001853.

PLoS Biology Primer:

Moen D, Morlon H (2014) From Dinosaurs to Modern Bird Diversity: Extending the Time Scale of Adaptive Radiation. PLoS Biology 12(5): e1001854

ScienceNOW: How Birds Survived the Dinosaur Apocalypse by Michael Balther

Museum Diaries Dinos ReDiscovered Episode Airs

April 28, 2014

Museum Diaries” is a six-part series commissioned by TVO to celebrate the inner workings of the Royal Ontario Museum during its centennial year. “Dinos Rediscovered” embarks on a stunning journey following the ROM Vertebrate Paleontology team on a field expedition to the Alberta badlands to discover treasures from 75 million years ago. This episode also features PM Project Manager Jason French and his team as they carefully deconstruct one of the ROM’s recent dinosaur exhibits, Ultimate Dinosaurs: Giants of Gondwana, and prepares the exhibition to travel to other Museum.

Learn more here.

 

David Evans

In Alberta with a truck load of dinosaur bones, as featured on the Museum Diaries episode.

Season’s Greetings from Santa Claws!

December 26, 2013
Season's Greetings from the Cretaceous Santa Claws by Danielle Dufault

Season’s Greetings from the Cretaceous Santa Claws by Danielle Dufault

Check out this fun and fanciful holiday ecard from talented paleoartist Danielle Dufault, which incorporates the latest data on the mysterious theropod Deinocheirus mirificus- now revealed to have stayed enigmatic so long due to strong connections with the master of secrecy Santa himself. Awesome job Danielle!

New Hell Creek Dromaeosaurid Described

December 16, 2013
Holotype maxilla and associated dentary of Acheroraptor temertyorum. Copyright Royal Ontario Museum.

Holotype maxilla and associated dentary of Acheroraptor temertyorum. Copyright Royal Ontario Museum.

Today we formally announced publication of a new species of a small, meat-eating dinosaur (‘raptor’) based on newly discovered fossils from Montana, USA. Acheroraptor temertyorum is based on associated upper and lower jaw fossils from the Hell Creek Formation of Montana. It was relatively large for a “raptor”, approaching Deinonychus in size, with a long-snouted skull and dagger-like ridged teeth.

Acheroraptor was one of the last non-avian dinosaurs. It lived 67 to 66 million years ago in western North America, in a community that included Tyrannosaurus rex and  Triceratops. As such, Acheroraptor gives us a more complete picture of the ecosystem in North America just before the great extinction that marked the end of the Age of Dinosaurs.

The unique ridged teeth of Acheroraptor have been recognized for decades, but the lack of reasonably complete diagnostic material did not permit determination of the taxonomic affinities and evolutionary relationships of the Hell Creek dromaeosaur until now.  Interestingly, the jaw bones of Acheroraptor compare more closely to those of Velociraptor and other long-snouted Asian species than those of older North American species. Dromaeosaurid evolutionary relationships and biogeography will continue to be contentious. Phylogenetic analysis based on the dataset of Longrich and Currie (2009) recovered Acheroraptor as a velociraptorine dromaeosaurid, nested within a group of Asian species. The close evolutionary relationship of Acheroraptor to a  group of late-occurring Asian species that includes Velociraptor suggests that migration from Asia may have continued to shape North American dinosaur communities right up until the end of the Cretaceous period.

The research describing Acheroraptor was published in the latest issue of Naturwissenschaften:

Evans, D. C.,  D. Larson, and P. J. Currie. 2013. A new dromaeosaurid (Dinosauria: Theropoda) with Asian Affinities from the latest Cretaceous of North America. Naturwissenschaften 100 (11): 1041-1049. Available online here.

The Press Release from the Royal Ontario Museum can be found here.

Two Acheroraptor feeding at a Triceratops carcass as Tyrannosaurus rex approaches. Courtesy of Julius Csotonyi .

Two Acheroraptor feeding at a Triceratops carcass as Tyrannosaurus rex approaches. Courtesy of Julius Csotonyi .