One of the earliest known dinosaur species, the Eoraptor lived during the Upper Triassic period in what is now Argentina. It was a small, slim creature, probably no more than 3 feet (1 meter) long from nose to tail. It bore similar features to later theropod dinosaurs, including sharp teeth, powerful hind legs, and characteristic three-fingered hands. Despite this, there was still much debate over whether the Eoraptor was actually an early theropod or perhaps a close relative instead.

Key Facts

Eoraptor pronunciationEe-oh-rap’-ter
What does Eoraptor mean?Dawn Plunderer
Dinosaur typeTheropod
On the menuOmnivorous
Length3.2 feet (1 meter)
Height1.1 feet (35 centimeters)
Weight22 lb (10kg)
Life expectancy40 years
Legs used to get aroundBipedal
Estimated top speed18 mph (29 km/h)
When they livedUpper Triassic, 228 million years ago
Where they have been found?Argentina, North America

When & Where

Remains of this dinosaur were first discovered in 1991 by Ricardo Martinez, a paleontologist from the San Juan National University in Argentina. The fossils were found in a muddy siltstone layer known as the Ischigualasto Formation, which dates back to the Late Triassic period, around 228 million years ago.

It was later named and described in 1993 by Paul Sereno, Catherine Forster, Alfredo Monetta, and Raymond Rogers, who called it Eoraptor lunensis. The name means “dawn plunderer,” derived from the Greek “eos,” meaning dawn (a reference to its place as one of the earliest dinosaurs), and “raptor,” meaning thief or plunderer (possibly referring to its grasping hands). Lunensis is a Latin reference to its place of discovery, Valle de la Luna (Valley of the Moon), in San Juan Province, Argentina.

Size & Weight

The Eoraptor was a small, slender dinosaur about the same size as a large house cat. It is thought to have measured roughly 3 ft (1 meter) long from nose to tail and stood about 1.1 ft (35 cm) tall. It is estimated to have weighed around 22 lb (10 kg).

Mobility & Diet

This dinosaur was bipedal, meaning it moved around on two legs. It is thought to have had a top speed of 18 mp/h (29 km/h).

The Eoraptor was probably an omnivore that ate plants and animals. It may have fed on one type of food primarily and supplemented its diet with the other. Since it lacked a sliding jaw joint and had weak teeth, it probably did not hunt large prey.

Interesting Points

  • Despite being bipedal, this dinosaur could run on all fours if necessary.
  • Its dentition was strikingly similar to that of the later theropod dinosaurs.
  • Eoraptor is considered one of the earliest dinosaurs ever, although its place in the family tree is still uncertain.
  • Eoraptor is one of the most primitive dinosaurs and provides important clues about the early evolution of dinosaurs.

Featured Image Credit: Conty, CC BY 3.0, via Wikimedia Commons