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Dinosaur survived fearsome bite of hungry T. rex and left new evidence of ancient hunting

  • A Tyrannosaurus rex dinosaur replica at the Woodland Park Zoo in Seattle. Scientists have unearthed a dramatic remnant of an encounter between a Tyrannosaurus rex and a creature that got away, providing strong new evidence that the famous dinosaur hunted for food.AP Photo/Elaine Thompson

  • July 15, 2013: Researchers Robert A. DePalma II, left, and David A. Burnham show a Tyrannosaurus rex tooth crown embedded between the vertebrae of a hadrosaur and surrounded by bone overgrowth. That regrowth shows the duckbill was alive and not just a carcass when it met the T. rex, so the fossil provides definitive evidence that T. rex hunted live animals.AP Photo/David A. Burnham

  • A bronze cast of the Tyrannosaurus rex skeleton known as the Wankel T.rex, in front of the Museum of the Rockies at Montana State University in Bozeman, Mont.AP Photo/Museum of the Rockies

  • Jack Horner, Curator of Paleontology at Museum of the Rockies, providing scale for Tyrannosaurus rex fossils at excavation site near the Fort Peck Reservoir, Fort Peck, Mont.AP Photo

The fearsome bite of a hungry Tyrannosaurus rex left behind new evidence that the famous beast hunted for food and wasn't just a scavenger.

Researchers found a part of a T. rex tooth wedged between two tailbones of a duckbill dinosaur unearthed in northwestern South Dakota. The tooth was partially enclosed by regrown bone, indicating the smaller duckbill had escaped from the T. rex and lived for months or years afterward.

'[It's] extremely strong physical evidence that the attacker was a tyrannosaur.'

- Researcher Thomas Holtz, Jr., of the University of Maryland.

Since the duckbill was alive and not just a carcass when it met the T. rex, the fossil provides definitive evidence that T. rex hunted live animals, researchers say in Monday's issue of the Proceedings of the National Academy of Sciences.

The fossil, from around 67 million years ago, indicates the T. rex bit the duckbill from behind and "intended to take it for a meal," said David Burnham of the University of Kansas, an author of the report.

It's not clear whether there was a chase involved, he said.

Experts who didn't participate in the study said there was already ample evidence that T. rex went after live animals as well as scavenging carcasses. It brought a bone-shattering bite and teeth up to a foot long to each task.

The new fossil is the first to include a T. rex tooth embedded in the bones of its prey, giving "extremely strong physical evidence that the attacker was a tyrannosaur," said Thomas Holtz, Jr., of the University of Maryland.

"It's one other bit of evidence [for hunting] fully consistent with the other data already established from lots and lots of lines of evidence," Holtz said.

You might think a T. rex would take down anything in sight, but Jack Horner of Montana State University said it apparently preyed on the weak, the sick and the young instead.

It makes sense that T. rex also scavenged, said Kenneth Carpenter, curator of paleontology at the Utah State University East Prehistoric Museum.

"If there's a free meal, why not?" he asked. But decay can make carcasses toxic after a while, he said, and "at that point, T. rex is going to have no choice but to hunt."