Eoraptor was one of the world's earliest dinosaurs. It was a two-legged meat-eater that lived between 230 and 225 million years ago in the northwestern region of Argentina. Its name means "dawn plunderer from the Valley of the Moon", where it was originally discovered. Paleontologists believe the Eoraptor resembles the common ancestor of all dinosaurs. It is known from several well preserved skeletons.

Description and behavior

It had a thin body that grew to about 1 meter (3 feet) long, and weighed about 10 kilograms (22 pounds). It ran digitigrade, upright on its hind legs. Its arms were only half the length of its legs, and had five fingers on each hand. Three of those fingers, the longer of the five, ended in large claws and were used to handle prey. Scientists have surmised that the fourth and fifth fingers were too tiny to be of any use in hunting.

Eoraptor probably ate mostly small animals. It was a swift sprinter, and upon catching its prey, it would use claws and teeth to tear the prey apart.

Early dinosaur

The bones of this primitive dinosaur were first discovered in 1991, and by 1993 it had been determined to be one of the earliest of the "terrible lizards" (dinosaurs). Its age was determined by several factors, including its lack of specialized predatory features. Unlike later carnivores, it didn't have a sliding joint in its lower jaw to hold prey with. Also, only some of its teeth were curved and saw-edged. All of the teeth in a modern predator's mouth are shaped so.

Eoraptor belonged to a major group of dinosaurs called saurischians, or lizard-hipped dinosaurs. Their hip structures are similar to that of the modern lizard.

Eoraptor is more ancient than even the Herrerasaurus, and only some prosauropods recently discovered in Madagascar are older.