Name means: Hollow Form
Range: Late Triassic (Norian-Sinemurian, 221-190 MYA) from New Mexico, Arizona, Colorado, Texas, Zimbabwe, possibly Utah, Connecticut, and South Africa
Size estimate: 8-10 ft length, 40-50 lbs
Discovery: Edward Drinker Cope, 1889
Classification: dinosauria, saurischia, therapoda, coelophysoidea, coelophysidae
For such a lightly built animal, Coelophysis fossils rank among the most common dinosaurs. A site at Ghost Ranch, New Mexico preserves hundreds of their skeletons. Footprint fossils known as Grallator might belong to Coelophysis as well. If so, they and other fossils show that this animal and its relatives ranged across North America, Europe, and as far away as Africa. During the Late Triassic, the continents we now know all belonged to a giant landmass called Pangaea. A long-legged animal like Coelophysis would have no trouble spreading across a wide part of that supercontinent. Coelophysis’ long legs also made it fast. It needed all the speed it could get. Dinosaurs still coexisted with many other branches of the archosaur family tree. Many of these animals looked and acted like four-legged versions of the large theropods that would succeed them. Coelophysis would also need quick movement for catching prey. A 2009 in-depth study of Coelophysis found that thigh bones of adults thickened as they grew. Unlike mammals, which tend to slow down as they grow older, these animals stayed as swift proportionately as they were when younger. With longer strides as adults, that means they got slightly faster.
A ring of bones supported Coelophysis’ eye. Studying similar “sclerotic rings” from birds and lizards helps scientists reconstruct its visual capabilities. Coelophysis had a large, round eye with vision like a hawk’s. The field of vision in each eye overlapped to give this animal depth perception. Predators like Coelophysis need to be able to tell how far away their prey is to catch it. Its eyes functioned best in full daylight, which means its pupil likely had a round shape.
Coelophysis might be one of the few dinosaurs where scientists can tell male from female. Half the population had relatively thinner bones than the other. The thin-boned versions also had longer skulls and necks, shorter arms, and fused hip bones. The differences in hip bones have led some scientists to conclude the thinner skeletons belonged to females.