Friday, January 29, 2010

More Teeth Than T.rex

New Tyrannosaur Had More Teeth Than T. Rex

The newly found toothy tyrannosaur featured a hole in its skull and was recovered from New Mexico.

By Jennifer Viegas Thu Jan 28, 2010 07:00 PM ET
Discovery News

A newly found 29-foot-long tyrannosaur flashed more teeth than the well-known Tyrannosaurus rex, with which it shared a common ancestor, according to a paper in the latest Journal of Vertebrate Paleontology.

Remains of the badlands dinosaur, Bistahieversor sealeyi, were collected in the first paleontological excavation from a federal wilderness area, the Bisti/De-na-zin Wilderness of New Mexico. The dino's remains were removed VIP-style, airlifted by a helicopter operated by the Air Wing of the New Mexico Army National Guard.

"Bistahieversor sealeyi is the first valid new genus and species of tyrannosaur to be named from western North America in over 30 years," said co-author Thomas Williamson, curator of paleontology at the New Mexico Museum of Natural History.

It lived 74-75 million years ago, close to 10 million years before T. rex emerged. The earliest known tyrannosaurs date to about 167 million years ago and came from the American West, according to Carr. It is now therefore believed that the rough and tumble Tyrannosauridae family was born in the U.S.A.

Several features distinguish the new dinosaur, according to Williamson's partner on the project, Thomas Carr, who is director of the Carthage Institute of Paleontology and an assistant professor of biology at Carthage College.

It had around 64 teeth, while adult T. rex, had just 54.

However, Carr added, "The teeth of B. sealeyi were smaller and narrower than those of T. rex, which had the largest teeth among the tyrannosauroids."

The new dinosaur also had an unusual hole in its head, just above the eyes. The hole has not been seen on any other tyrannosaur, and might have helped to lighten the load of its head.

"The opening above the eye was produced by an air sac within the skull that removed bone where it was not needed," said Carr. "The opening would not have been visible when the animal was alive (because) it would have been covered by skin."

The dinosaur also had a "complex joint at its forehead." Carr explained that usually these animals show three prongs of the snout extending into the forehead, but the New Mexico beast had seven.

This complex joint might have functioned to stabilize and prevent motion at the joint," he said.

B. sealeyi additionally possessed a keel, or prominent ridge, that extended from the bottom edge of its lower jaw. The scientists aren't sure of the ridge's purpose, but it is another unique feature.

The researchers now think the deep snout characteristic of many tyrannosaurs evolved in the common ancestor of these animals, which lived west of the Western Interior Seaway, a shallow sea that split North America into two subcontinents during the Late Cretaceous.

Tyrannosaurs to the west of the sea continued to evolve this striking head feature, according to Carr, while those to the east retained the more primitive shallow snout. He believes that "selective pressures necessary for producing a deep snout were simply not in action" on the eastern side of the sea.

The badlands dinosaur along with other fossils collected from the Bisti site and from the lands of the Navajo Nation are currently on display at the New Mexico Museum of Natural History.