Coelophysis was a dinosaur, a group of extinct reptiles of the Mesozoic Era. Dinosaurs are readily distinguished from other reptiles by their upright limb postures in which the limbs are beneath (or nearly beneath) the body, not sprawled out to the sides of the body. The hip joint of Coelophysis demonstrates that the hindlimb was held beneath the body when the dinosaur walked or ran.
Coelophysis was a theropod dinosaur. Theropods were the meat-eating dinosaurs, and range from Coelophysis, one of the earliest theropods of the Late Triassic, to Tyrannosaurus, one of the last theropods of the Late Cretaceous. Known from hundreds of skeletons found at Ghost Ranch, New Mexico, Coelophysis is one of the best known theropod dinosaurs.
Among theropods, Coelophysis belongs to a group of primitive Triassic-Jurassic meat eaters called the ceratosaurs. These theropods had many fused bones in their hips and hindlimbs that helped to produce strong hind limbs for rapid running. Besides Coelophysis, Early Jurassic Dilophosaurus from Arizona is one of the better known ceratosaurs.