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07/15/2013

Tooth stuck in dino tail proves T-Rex wasn't a scavenger

Trex
Tyrannosaurus rex tooth crown embedded between hadrosaur vertebrae and surrounded by bone overgrowth. (Image courtesy of David A. Burnham)

 

Tyrannosaurus Rex may be known and loved as a terrifying, tooth-gnashing uber-predator. But in some quarters the tyrant king of the dinosaurs gets no respect -- no respect at all. 

Some paleontologists have argued that T Rex was not a predator but a lowly scavenger, the turkey vulture of the late Cretaceous. 

But on Monday, U.S. researchers announced they had discovered "conclusive evidence" that T Rex was a predator: a tyrannosaurus tooth embedded in the fossilized tail bones of a hadrosaur.

After the T Rex deposited its tooth in the poor hadrosaur, the vertebrae recovered from a massive infection and kept growing around the injury. That bone growth is the crucial piece of evidence, showing that the tooth was left by a predator pursuing live prey (that somehow got away), rather than embedded in a dinosaur that was already dead and being scavenged as carrion. 

The location of the tooth -- in the tail of the hadrosaur -- also suggests the T Rex was in pursuit of its prey, and gnashing at its hindquarters the way modern predators often do.  

"Such evidence is rare in the fossil record for good reason -- prey rarely escapes," the authors write in the new study, published in Proceedings of the National Academy of Sciences. The fossilized tail chunk was discovered in the Hell Creek Formation of South Dakota.

Bite traces attributed to T Rex have been discovered on smaller dinosaurs before.

But the problem is that those marks could just as well have been left by a scavenger gnawing on a dead dino as a predator chewing up an animal it caught live. Same goes for evidence of juvenile hadrosaur bones that were partially digested and associated with T Rex fossil remains: no conclusive evidence those babies were chewed up live, rather than swallowed post-mortem. 

 As the authors write, "One of the most daunting tasks of paelontology is inferring the behaviour and feeding habits of extinct organisms."

No kidding.

Kate Allen is the Star's science and technology reporter. She once spent a week digging up dinosaur bones in Alberta's badlands for the paper. Find her on Twitter at @katecallen.


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