Scientists have discovered the fossilized remains of a new meat-eating dinosaur in a quarry in New Mexico. They say the finding sheds light on the evolution of these extinct creatures.
Paleontologists say the dinosaur they call Tawa, named for the Hopi Native American sun god, was about the size of a large dog, but with a longer tail, stood about 70 centimeters tall at the hips and was two meters long. The two-legged creature also had razor-sharp teeth for eating meat.
Scientists conducting an analysis of the newly-discovered, 215 million year old fossils and other early dinosaur remains say Tawa also had the characteristics of two other dinosaurs - the giant, plant-eating sauropod and the horned Triceratops.
They believe Tawa is the common ancestor of both dinosaur groups that migrated from Argentina to other parts of the world during the Pangea period, between 200 and 300 million years ago, when geologists say the Earth's continents were compressed into a single landmass.
The fossil discovery suggests that Tawa also used a land bridge from South America to make its way to North America, when Tyrannosaurus Rex began evolving into modern day birds, according to Sterling Nesbitt, a researcher at the University of Texas who led a team of excavators.
"Tawa is a little bit of a surprise because it's preserving these very early traits that we see in dinosaurs while living with animals that are much more closely related to bird," said Nesbitt.
According to Nesbitt, Tawa might answer important questions about a dinosaur called Herrerasaurus, which was discovered in Argentina in the 1960s.
Herrerasaurus has traits like T. Rex - including sharp claws and teeth - but lacks other characteristics of the carnivore. Scientists hope to determine whether Herrerasaurus is a direct descendant of Tawa or part of a different species of dinosaurs.
Nesbitt say the Hayden Quarry in northern New Mexico, where the ancient fossils were unearthed, is a rich bed containing other prehistoric bones and artifacts. He says he plans to continue digging at the site to learn more about Tawa.
"We want to know how it grew, how the features changed as the animal got older," he said. "We also want to look at the anatomical details."
A description of the new dinosaur species is reported this week in the journal Science.