Shown is a tyrannosaur fossil marked with serrated tooth marks.
Matthew McLain
Meet the Top 10 Meat-Eating Dinos: Photos
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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 Tyrannosaurus rex , 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 T. rex ." "Tyrannosaurs were an ancient group that originated more than 100 million years before T. rex , and for almost all of their evolutionary history they were small carnivores not much bigger than a human in size." New T-Rex Tracks Add to Pack-Hunting Theory
Neil Thompson, Flickr
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"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. Dinosaurs That Loved the Nightlife
Nobu Tamura, Wikimedia Commons
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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."
Nobu Tamura, Wikimedia Commons
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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. Nests of Big-Clawed Dinosaurs Found in Mongolia
Wikimedia Commons
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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. New Dinosaur Bolsters Bird-Dino Connection
Wikimedia Commons
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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 " chicken from hell " -- 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.
Mark Klingler, Carnegie Museum of Natural History
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"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. World's Earliest Bird Discovered
Nobu Tamura, Wikimedia Commons
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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." Velociraptor Inspires Fast Running Robot
Nobu Tamura, Wikimedia Commons
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"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." Tiny Feathered Dinosaur Found
Wikimedia Commons
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"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." Photos: Audubon Report Names Birds at Climate Risk
Kevin Law, Wikimedia Commons
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Sixty-six million years ago, a tyrannosaur may have sunk its sharp and serrated teeth into the bones of another tyrannosaur, new research suggests.
A huge triceratops skeleton was found in Wyoming. But researchers are saying it's not a triceratops -- that dinosaur never existed. Wait, what?
DCI
The gnawed bone may provide evidence that tyrannosaurs ate their own kind, the researchers said.
"We were out in Wyoming digging up dinosaurs in the Lance Formation," paleontologist Matthew McLain of Loma Linda University in California said in a statement. "Someone found a tyrannosaur bone that was broken at both ends. It was covered in grooves. They were very deep grooves." [ Paleo-Art: Dinosaurs Come to Life in Stunning Illustrations]
The grooves looked like tooth marks, he said. It appeared that a large, toothy creature had bitten off the tyrannosaur's flesh, pulling it in the direction perpendicular to the bone — much like a person eats a piece of fried chicken. At least 10 separate grooves of varying widths — with the widest reaching 0.1 inches (5 millimeters) across — were etched into the dinosaur's long bone.
But one groove caught the researchers' attention. Located on the bone's wider end, the groove contains smaller parallel grooves that were likely created when the diner turned its head, dragging its serrated teeth across the bone.
Marks from the serrated teethmay help identify the culprit, the researchers said. Crocodiles have large teeth and bite forces, but their teeth aren't serrated. So the researchers crossed these fierce reptiles off the list. But theropods, mostly meat-eating dinosaurs that walked on two feet, did have sawlike teeth.
"These scores were likely made by a theropod dinosaur, and the width of the larger grooves suggests the traces were made by a tyrannosaur," the researchers wrote in their unpublished findings, presented at the Geological Society of America's 2015 annual meeting in Baltimore on Sunday (Nov. 1).
The only large theropods found in that Wyoming formation are tyrannosaurs — Tyrannosaurus rex and Nanotyrannus lancensis , they said. ( Nanotyrannus is a controversial species. Some paleontologists maintain it's a relative of T. rex , and others say it's a T. rex juvenile.) But, based on the presence of the Tyrannosaurus and Nanotyrannus fossils in the area, it's possible that these species left the gnaw marks on the bone, indicating that tyrannosaurs were cannibals, McLain said.
"This has to be a tyrannosaur," McLain said. "There's just nothing else that has such big teeth."