Eoraptor

Eoraptor ("dawn thief" ) is one of the earliest known dinosaurs. It lived in the Late Triassic Period of Argentina.

Description
Eoraptor measured approximately 1 meter in length, and is estimated to have weighed about 10 kilograms. It had lightly built bones, and in fact its leg bones were hollow. Eoraptor had five digits on each hand, although the fourth and fifth digits were too small to be used regularly.

Classification and History
After being discovered in 1991 in the Ischigualasto Formation of Argentina, Eoraptor was described in 1993 by Paul Sereno and colleagues as one of the earliest dinosaurs. Originally, it was described as a primitive theropod, a position supported by several subsequent studies. However, it has also been suggested that Eoraptor is in fact a primitive sauropodomorph. It is generally agreed that Eoraptor was an early saurischian, but a more precise classification is as yet uncertain.

Habitat
Triassic Argentina was a warm and humid floodplain, subject to strong rainfall. As such, the vegetation in the area was lush and diverse. Herrerasaurus and Pisanosaurus were dinosaur contemporaries of Eoraptor, and they lived with other reptiles such as rauisuchians, dicynodonts, and aetosaurs. These animals were much more common than early dinosaurs.

Diet
Eoraptor is thought to have been an omnivore, eating both animals and plants. It had both curved, serrated teeth like theropods, and broad, leaf-shaped teeth like sauropodomorphs.