July 15, 2009--Don't let the Wolverine-like claws fool you. Unlike the X-men's most popular pugilist, this new dinosaur species was no predator, scientists say.

Dubbed Nothronychus graffami, the 13-foot-tall (4-meter-tall) therizinosaur (reconstructed skeleton pictured) lived about 92.5 million years ago in what is present-day Utah.

N. graffami's claw bones are 9 inches (23 centimeters) long. But in life, sheathed in hornlike keratin, the talons would have each been about a foot (30 centimeters) long, or about as long as the dinosaur's head.

(Related: how therizinosaurs shed light on dinosaur growth.)

In addition to its imposing claws—a therizinosaur trademark—the newfound dinosaur had a less-than-fearsome potbelly, a birdlike beak, stumpy legs, and a short tail, according to a report published online today by the journal Proceedings of the Royal Society B.

N. graffami's leaf-shaped teeth and big belly suggest the animal was a plant-eater—so why the killer claws?

"We really don't know," said study team member Lindsay Zanno of the Field Museum in Chicago.

"There are some things we can rule out, such as digging. Other than that, the claws may have been used for defense, to forage for plants, or to attract mates."

As distant cousins of T. rex and Velociraptor, N. graffami and other therizinosaurs suggest that those predators may have plant-eaters in their ancestry, Zanno added.

—Ker Than