Eoraptor was one of the world’s earliest known dinosaurs. It lived between 230 and 225 mya (million years ago), in what is now known as Argentina. Several well-preserved skeletons have been found and it is believed that the Eoraptor resembles the common ancestor of all dinosaurs. The type species is E. lunensis, which means “dawn plunderer of the Moon”. The fossils were first discovered in 1991 by University of San Juan paleontologist Ricardo Martinez in the Ischigualasto Basin of Argentina. This area was a river valley during the Late Triassic, but is now desert badlands.

It had a thin body that was about 3 feet long. It weighed about 22 pounds. Eoraptor ran upright on its hind limbs. Each hand had five digits, with the three longest digits on each hand having large claws, most likely used to handle prey. It is believed that the other two digits on each hand were too small to achieve any purpose in hunting.

Eoraptor was a two-legged meat-eater. The age of Eoraptor was determined based on several features studied in fossil records. Unlike later carnivores, it lacked a sliding joint of the lower jaw, which was key to holding large prey. Only some of its teeth were curved and saw-edged, unlike those of later predators. It most likely ate small animals. It was a fast sprinter and, upon catching its prey, it would use its claws and teeth to tear it apart. It is possible that this specimen was omnivorous, as it had both carnivore-type teeth and herbivore-type teeth.