Tyrannosaur Mauled by Kin

Dinosaur hunters have unearthed the jaw of a tyrannosaur only to find a tooth from a fellow tyrannosaur dug into the bone.

It's the most striking evidence yet that the family of fearsome beasts were a rough-and-tumble bunch.

Phil Bell and Phillip Currie of the University of Alberta think the dinosaur that got bitten was most likely an eight- to nine-meter-long (26.2- to 29.5-foot-long) Gorgosaurus, a smaller cousin of Tyrannosaurs Rex.

Their report on the new specimen was published this month in the journal Lethaia.

Tyrannosaurs had a penchant for carving each other up. Fossil jaw bones raked with tooth marks are not uncommon, and scientists have figured they were leftovers from a familial tiff over territory, a mate or some particularly rough sexual encounter.

"Either they were really scrappy animals and fought often, or it's some kind of sexual behavior," Currie said. "Sea otters really bite up females on the face during mating, for example."

It's rare to find dinosaur teeth embedded on others' bones, and the find is a first for confirming tyrannosaur-on-tyrannosaur violence.

It also comes with a CSI-like forensic twist: There is no new bone growth around or over the tooth, indicating that bitten dinosaur died within two weeks after being wounded.

That opens up an additional possibility: cannibalism. The bitten animal may have already been dead before it was chomped.

Currie doesn't think so, though tyrannosaurs had strong teeth, but the one they found embedded in the jaw bone isn't whole; it's been snapped off.

"That kind of torque suggests both animals were alive and fighting when this happened," he said. "There are animals well adapted to biting through bone. It doesn't make sense that the tooth would break if it was biting something that was dead already."

Tyrannosaurs replaced their teeth about once every two years or so, so a broken tooth wasn't a big deal.

Still, the animal that did the biting meant business. The researchers estimate it took 6,053 Newtons (1,361 pounds) of bite force to do the kind of damage they found.

"There's some evidence of face biting behavior in tyrannosaurs," said Gregory Erickson of Florida State University in Tallahassee. "It seems to be how they settled disputes."

It's impossible to say for sure whether this particular scuffle is what killed the recipient of the bite, but Erickson said it must've been one heck of a show.

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