Friday, August 20, 2010

Deinonychus was puny compared to Tyrannosaurus, but it was a very different kind of predator. It was a member of a group of dinosaurs called dromaeosaurids which are popularly known as raptors. With long arms tipped with fingers bearing recurved claws, a mouth full of serrated teeth, and a sickle-like claw borne on a hyperextendable second toe, Deinonychus has classically been portrayed as a grappler which used its arms and legs to bring down larger prey while acting in a group.

A recently recovered skeleton of the herbivorous dinosaur Tenontosaurus from Wyoming exhibits different kinds of bite marks and was found surrounded by tooth fragments of Deinonychus.

Given its array of weaponry, it has seemed unlikely that Deinonychus was capable of the heavy bite forces exerted by other predatory dinosaurs with large heads and small forelimbs, but the damage done to the right forelimb of the Tenontosaurus skeleton showed that Deinonychus was indeed capable of a bone-puncturing bite.

In a study published July 4 in the Journal of Vertebrate Paleontology, scientists led by Paul Gignac of the University of Florida in Tallahassee used latex to fill in the punctures to create casts of their shape. They were able to determine the holes were probably made by a large, adult Deinonychus holding the Tenontosaurus forelimb in the front, right part of its jaws.

To investigate what kind of pressure was required to produce this damage, the scientists made a replica Deinonychus tooth out of nickel, which was pressed into a series of cow limb bones. The paleontologists found that it took about 4,100 Newtons of force to drive the artificial Deinonychus tooth into the cow bones, similar to the bite of hyenas and lions. They estimate that the back of the dinosaur’s jaw could have exerted up to twice as much force, similar to those recorded from adult American alligators, and much more powerful than previously thought.

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