Meat-eating mega-dinosaur species found in Argentina

Paleontologists digging in the arid Patagonian wilderness of Argentina on Monday reported finding the remains of a meat-eating dinosaur as big as Tyrannosaurus rex and perhaps clever enough to bring down its prey by hunting in packs.

Researchers said that by working together, the dinosaurs may have been able to kill animals much bigger than themselves, including the 125-foot, 100-ton Argentinosaur, a plant-eating behemoth that may have been the largest land animal that ever lived.

"Whatever they could cut out, they would go after," said paleontologist Philip Currie, of Canada's University of Alberta. "They were really bulky animals, but Argentinosaurs were even slower. You only have to be faster than whatever you're chasing."

The new discovery, in Argentina's southern Neuquen province, added fuel to an ongoing debate about the behavior of predatory dinosaurs that were themselves so large and unwieldy that some researchers have speculated the adults may have had to forsake hunting for scavenging.

But Currie said the Argentine site had the remains of at least seven animals from 18 feet to 40 feet long, suggesting they may have been a herd or family in which different group members could provide either speed or strength.

"It's certainly an intriguing idea," said paleontologist Peter Makovicky, of Chicago's Field Museum. "The problem, though, is that when you have only one incidence you really don't know what's going on."

Reporting in the current issue of the French journal Geodiversitas, Currie and Rodolfo Coria, of the Museo Carmen Funes, in Plaza Huincul, Argentina, named the new animal Mapusaurus roseae.

Currie said the researchers found hundreds of bones in a sandstone deposit. He said the fossils were 100 million years old, and appeared to have been carried away by a flash flood.

"The river was running very fast when they were buried in it," Currie said. "It was a single event in a short amount of time." He said the deposit did not contain the bones of any other species of dinosaur, a rare occurrence for meat-eaters.

Currie said the Mapusaurs, similar to other Southern Hemisphere predators, were probably slightly bigger than T. rex, which is found only in the Northern Hemisphere.

Although both animals were large, bulky "macropredators" that walked on their hind legs and used their teeth as their basic weapons, there were significant differences.

"Mapusaurs have long, thin skulls with knifelike teeth and jaws that can close very fast," Currie said. "T. rex has a short skull with powerful, banana-shaped teeth better for biting through bone."

T. rex was equipped to attack and destroy animals its own size, Currie said, but Mapusaurs perhaps could "go in, strike, pull and see what to do next," a strategy that could work against larger animals, especially if they attacked together — the prehistoric equivalent of a pack of wolves cornering a bison.