Clues to dinosaur origins found in fossils

SALT LAKE CITY, Dec. 10 (UPI) -- U.S. paleontologists say they've determined the first dinosaurs to evolve about 230 million years ago meandered across a single super-continent.

The researcher team said it reached its conclusion from the discovery of 213-million-year-old fossils of the previously unknown carnivorous dinosaur Tawa hallae, recovered from a northern New Mexico dig.

The scientists said fossil bones of several individual dinosaurs were recovered, but the Tawa type specimen is a nearly complete skeleton of a juvenile that stood about 28 inches tall at the hips and was about 6 feet long -- about the size of a large dog, but with a much longer tail.

Based on an analysis of the relationships between Tawa and other early dinosaurs, the researchers hypothesize dinosaurs originated in what is now South America, and then dispersed into regions that later became separate continents.

The finding suggests each carnivorous dinosaur species descended from a separate lineage before arriving in North America, instead of all evolving from a single ancestor, said Randall Irmis of the Utah Museum of Natural History.

"We think all the major dinosaur groups had the ability to get to North America," but for some reason only the carnivorous dinosaurs found the North American climate to be hospitable at that time, Irmis said.

"This new dinosaur, Tawa hallae, changes our understanding of the relationships of early dinosaurs and provides fantastic insight into the evolution of … the first carnivorous dinosaurs" Irmis added.

The research appears in the journal Science.