The fossil of a never-before seen species of dinosaur that could have been among the first to roam the planet 230 million years ago has been unearthed in Argentina, a study said Thursday.

A fossil of the petite, two-legged Eodromaeus, which means "dawn runner," was found in Ischigualasto, a well-explored rock formation in northwestern Argentina that has yielded hundreds of precious fossil discoveries.

Scientists say the find of two near-complete dino fossils right next to each other has helped shed light on the development of predatory dinosaurs known as theropods (which means beast-footed), including the famous T. Rex.

"It really is the earliest look we have at the long line of meat eaters that would ultimately culminate in Tyrannosaurus rex near the end of the dinosaur era," said Paul Sereno, University of Chicago paleontologist.

"Who could foretell what evolution had in store for the descendants of this pint-sized, fleet-footed predator?"

Fossils of small theropods are rare, and this one measures about two meters long (six feet). Scientists believe it weighed 10 to 15 pounds (4.5 to seven kilograms).

The Eodromaeus had a long neck and tail, sharp claws and biting canine teeth.

By examining its limbs, scientists believe they have found differences between the "dawn runner" and its contemporary, the Eoraptor, which they now believe belonged to a different family lineage, the huge, long-necked and four-legged sauropods.