National Geographic News
An illustration of the ''thunder thighs'' dinosaur as it may have appeared in life.
A "thunder thighs" dinosaur mother protects her offspring from a predator in an artist's conception.

Illustration courtesy Francisco Gascó, Mike Taylor, and Matt Wedel

Christine Dell'Amore

National Geographic News

Published February 23, 2011

A newfound dinosaur species that used its "exceptionally powerful" thighs to kick predators likely had a bad temper to boot, one expert says.

The 46-foot-long (14-meter-long) Brontomerus mcintoshi had an immense blade on its hipbones where strong muscles would have attached, according to a new study.

"These things don't happen by accident—this is something that's clearly functional," said study co-author Mathew Wedel.

The team suspects the dinosaur—a type of sauropod, or plant-eating, four-legged lumberer—used its massive legs to either maneuver over hilly ground or deliver "good, hard" kicks to predators, said Wedel, assistant professor of anatomy at Western University of Health Sciences in Pomona, California.

Brontomerus—"thunder thighs" in Greek—may have even attacked like a modern-day chicken, relentlessly kicking and stomping pursuers to death, he added.

"I could only imagine how ill-tempered these sauropods would have been," Wedel said—as are most birds, dinosaurs' modern-day descendants.

In both cases, "you've got a little brain, you're permanently paranoid about all these meat-eaters around, and you're trying to protect your young."

(See "New Strong-Handed Dinosaur May Shatter Assumptions.")

"Extreme" Dinosaur Roamed Prehistoric Serengeti

Thunder thighs' bones were first found in 1994, when scientists rescued two partial skeletons of the then unidentified dinosaur from a fossil quarry that had otherwise been looted in eastern Utah.

When Wedel and colleagues examined the bones in 2007, they realized they'd found a new species—and an "extreme" one at that, Wedel said. For instance, the shapes of the newfound species' bones showed it had the largest leg muscles of any sauropod yet found.

(See more pictures of bizarre dinosaurs in National Geographic magazine.)

B. mcintoshi likely needed such extreme defenses to fight off "terrifying" predators such as Deinonychus (picture) and Utahraptor (picture), raptors that lived alongside the plant-eater about 110 million years ago in the early Cretaceous period, he said.

The prehistoric animals roamed a landscape that would have resembled Africa's Serengeti, laced with rivers and mudholes and distinguished by vast, dry upland areas, Wedel noted. Herds of cowlike plant-eaters called Tenontosaurus would have dotted the plains. (Learn more about prehistoric animals.)

"If I could shoot you back in a time machine, it would have been like going on safari, except you'd want something more robust than a Land Rover—maybe a tank," he said.

"The sauropods were probably beautiful animals if you were a long way away with binoculars," he added.

"But up close, [they were] probably a nightmare."

The thunder thighs dinosaur is described in the most recent issue of the journal Acta Palaeontologica Polonica.

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