for National Geographic News
Scientists have uncovered a new species of dinosaur that roamed the long-gone Montana coastline around 150 million years ago.
Named Suuwassea emilieae, the 50-foot-long (15-meter-long) animal is a sauropod. Sauropods were plant-eating dinosaurs with long necks, whiplike tails, small heads, stubby legs, and huge bellies.
Montana has yielded many dinosaur fossils from the Cretaceous period (about 76 to 65 million years ago)most famously the fierce meat-eater Tyrannosaurus rex and the rhinoceros look-alike Triceratops.
But Suuwassea was found in a geological formation that formed during the Jurassic period (about 150 million years ago). The landform, known as the Morrison formation, extends from New Mexico to Montana.
"No new sauropod has ever been described from Montana," said Peter Dodson, professor of anatomy at the University of Pennsylvania's School of Veterinary Medicine and the Department of Earth and Environmental Sciences. "We thought that all Morrison dinosaurs were known, that the book was closed. And here we find a new dinosaur and perhaps fauna just crying out to be studied," he said.
The new dinosaur is unusual in several ways. Sauropods found in the Morrison formation farther south, such as Diplodocus and Apatosaurus, are typically 70 to 90 feet (21 to 27 meters) long. At roughly 50 feet (15 meters), Suuwassea is small for a sauropod. In addition, it has two unexplained holes in its skull.
"For the past hundred years people thought all the animals in the Morrison formation were the same," said Jerry Harris, a doctoral candidate in the University of Pennsylvania's Department of Earth and Environmental Science. "Preliminary indications suggest something weird, something ecologically different, is going on up there. Whether it was climate or humidity or something else are questions that need to be looked at."
Dodson and Harris suggest that environmental conditions led to a very different kind of evolutionary pattern for dinosaurs in the southern and northern regions of the western United States.
Dodson first learned of the Suuwassea fossil in September 1998. William Donawick, an emeritus professor of surgery at the University of Pennsylvania's School of Veterinary Medicine, had brought a bone back from a summer trip out West.
The bone preservation was quite good, so Dodson and his team of students and volunteers headed out to the site the following summer, expecting to find a fossil from the Cretaceous period.
When the fossil turned out to be in the Morrison formation, Dodson was initially disappointed.
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