Ostrichlike Dinosaur Covered in Fossilized Feathers
The find contains 'unparalleled' fossilized feathers and skin, anatomical features that aren't usually preserved in dinosaur remains.
The skeleton of a heavily feathered, ostrichlike dinosaur has "unparalleled" fossilized feathers and skin - anatomical features that aren't usually preserved in dinosaur remains, a new study reports.
The remains indicate that the dinosaur - an Ornithomimus, a fast-moving theropod (bipedal, mostly meat-eating dinosaurs) with an uncanny resemblance to an ostrich - sported a feathery coat during the Late Cretaceous, more than 66 million years ago.
Study lead researcher Aaron van der Reest found the partial skeleton in Alberta's Dinosaur Provincial Park in 2009, during his first undergraduate year at the University of Alberta. The newfound skeleton is just one of three feathered Ornithomimus specimens in the world, and the only one with a well-preserved tail, he said. [Images: These Downy Dinosaurs Sported Feathers]
"It's pretty remarkable. I don't know if I've stopped smiling since [excavating it]," van der Reest said in a statement. "We now know what the plumage looked like on the tail, and that from the midfemur down, it had bare skin."
Modern ostriches also have exposed bare skin, which they use to regulate their body temperature, the researchers said in the study. Given that the newfound Ornithomimus specimen has a lightly feathered neck and doesn't have feathers on its legs or the underside of its tail, perhaps it, too, used its bare skin for thermoregulation, they said.
"Because the plumage on this specimen is virtually identical to that of an ostrich, we can infer that Ornithomimus was likely doing the same thing - using feathered regions on their body to maintain body temperature," van der Reest said.
In fact, the fossilized feathers were crushed because of the weight of the sediment over them, but a scanning electron microscope revealed a 3D keratin structure of feathers on the dinosaur's tail and body.
"We are getting the newest information on what these animals may have looked like, how they maintained body temperatures and the stages of feather evolution," van der Reest said.
In addition, it provides more evidence that birds evolved from theropod dinosaurs.
"There are so many components of the morphology of this fossil as well as the chemistry of the feathers that are essentially indistinguishable from modern birds," said study co-researcher Alex Wolfe, an adjunct professor of paleobiology at the University of Alberta.
The adult specimen also has a skin impression next to its thighbone, just like the webs of skin living birds have. However, modern birds have a web that bridges the knee to the abdomen, whereas Ornithomimus has a web of skin from the midthigh to the abdomen.
"This is the first report of such soft-tissue structures in nonavian theropods," the researchers wrote in the study, which will be published in the March 2016 issue of the journal Cretaceous Research. The curious skin web may be a transitional feature between theropods and modern birds, they said.
In addition to shedding light on dinosaur feathers and skin, the finding may help paleontologists determine where to dig for fossils, the researchers said.
"If we can better understand the processes behind the preservation of the feathers in this specimen, we can better predict whether other fossilized animals in the ground will have soft tissues, feathers or skin impressions preserved," van der Reest said.
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An illustration of Ornithomimus shows long and short feathers covering most of its body.
Paleontologists have just assembled the most comprehensive family tree of meat-eating dinosaurs. Published in the journal Current Biology, the family tree reveals how diverse carnivorous dinosaurs were and how birds eventually evolved from them. Tyrannosaurs, including
, are one key group on the meat-loving dino family tree. Lead author Steve Brusatte of the University of Edinburgh's School of GeoSciences told Discovery News, "The most iconic dinosaurs of all, tyrannosaurs were more than just the 13-meter-long (nearly 43 feet long), 5-ton monster predator
." "Tyrannosaurs were an ancient group that originated more than 100 million years before
, and for almost all of their evolutionary history they were small carnivores not much bigger than a human in size."
"Some of the rarest theropods (two-legged carnivorous dinos) of all, compsognathids are represented by about half a dozen species," Brusatte said. "They were small, sleek meat-eaters which ate small prey like lizards." One of the more recent finds, Juravenator from Germany, is known from a nearly complete fossil.
Ornithomimosaurs were theropods called "ostrich mimic" dinosaurs -- for a reason. "Like living ostriches, they could run fast on their long legs and used their sharp, toothless beaks to eat a varied diet of small prey, plants, and perhaps even small shrimps in the water just like living flamingos," Brusatte explained. "A recent find in Canada showed that not only were ornithomimosaurs feathered, but they also had complex feathers on their arms that would have formed something of a wing, although they couldn't fly."
Brusatte describes therizinosaurs as "perhaps the weirdest theropods of all." "These were big, bulky, cumbersome dinosaurs that ate plants. They had fat barrel-shaped chests, stocky legs, and big claws on their arms," Brusatte said. For many years paleontologists argued about which group this dinosaur belonged to, only recently settling on theropods. This means they were fairly closely related to birds, despite their weird anatomy.
Alvarezsaurs were among the smallest dinosaurs of all, measuring just a few feet long and weighing less than 5 kilograms (10 pounds). "Some of them had only a single functional finger on their hand, which they probably used to prod deep into the nests of bugs, which were one of their main food sources," Brusatte said.
Oviraptorosaurs, were a group of small omnivores that were lightweight, lacked teeth and had tall, hollow crests on their skulls. The recently discovered Anzu -- the so-called "
" -- came by its nickname honestly. It towered more than five feet tall, weighed more than 400 pounds, and was covered in a coat of feathers.
"Troodontids were probably the smartest dinosaurs of all, as they had the largest brains relative to their body size of any dinosaur group," Brusatte said. "Most troodontids were small, fast-running dinosaurs that probably ate both meat and plants." Among the most recently discovered of this group are the small, feathered Anchiornis and Xiaotingia, which lived in China about 160 million years ago. "They look eerily similar to birds, so much so that some researchers think they could be primitive birds rather than troodontids with wings and feathers," Brusatte said.
Dromaeosaurids were "raptor dinosaurs" that include Velociraptor from "Jurassic Park" fame. These dinosaurs were pack hunters who wielded a sharp, hyper-extendable "killer claw" on their second toe. "One of the most recently discovered dromaeosaurids is Balaur, a poodle-sized terror from Romania which had not one, but two 'killer claws' on each foot."
"The oldest birds, like Archaeopteryx that lived 150 million years ago in Germany, are very hard to distinguish from their closest dinosaurian relatives," Brusatte said. "Unlike living birds, they had teeth, sharp claws on their wings, and long tails." "Over the past two decades," he continued, "over 50 new species of Mesozoic birds have been discovered in northeastern China, in the same rock units as the famous 'feathered dinosaurs.' So many birds are preserved here because entire ecosystems were buried by volcanic eruptions, turning animals to stone like a dinosaur version of Pompeii."
"The 10,000 species of birds that live today -- from hummingbirds to ostriches -- are modern dinosaurs," Brusatte said. "They are dinosaurs in the same way that humans are mammals. The classic body plan of living birds -- feathers, wings, wishbones, air sacs extending into hollow bones -- did not evolve suddenly but was gradually assembled over tens of millions of years of evolution. But, when this body plan finally came together completely, it unlocked great evolutionary potential that allowed birds to evolve at a super-charged rate." "They underwent a burst of evolution early in their history, which eventually led to the 10,000 species alive today -- more than twice the number of mammals."