Eoraptor is one of the earliest dinosaurs ever discovered. That means that this small dinosaur was one of the first to ever walk on Earth, and its success as a hunter helped determine what other dinosaurs would look like. Although it was small, it was a fierce predator. Its speed and intelligence are some of the reasons that dinosaurs replaced other animals as the dominant land creatures.
Discovered in 1993 in the Ischigualasto Basin in northwestern Argentina, the small skull was found in a single rock. Unlike most dinosaur discoveries, and to the delight of the team that found this important creature (Paul Sereno, Fernando Novas, and their team), an almost complete skeleton was found. This single creature has greatly increased scientists' knowledge of how dinosaurs developed and evolved. There are so few dinosaurs known from this time period that finding a complete skeleton of such an early member of the dinosaur family is a big help in expanding our knowledge of the early dinosaurs.
Eoraptor had the characteristics of later dinosaurs - serrated teeth, grasping hands (although there is some speculation that it occasionally walked using all four limbs), light hollow bones and a strong, light skull. Although it lived at the same time as the larger Herrerasaurus (which may have eaten Eoraptor), it has some significant differences. Some of its teeth were shaped differently and the bones in its hands were more primitive. Later dinosaurs tended to lose fingers, and by the time T. rex came onto the scene, it had only two fingers. Eoraptor had five. Even Herrerasaurus, which had five fingers, had a less useful fifth finger.
Eoraptor never appears in the novels or films. However it does possibly appear in an ambiguous picture in the comics.
Eoraptor can be created from paleo-DNA in Jurassic Park III: Park Builder.