Coelophysis

Phylogeny: Dinosauria > Saurischia > Theropoda > Neotheropoda > Coelophysoidea > Coelophysidae

Overview: Coelophysis is one of the best understood theropods from the Late Triassic, represented by a stupendous amount of fossil material, mainly from the southwestern United States. Fossils of the animal, consisting of some vertebrae and limb bones, were first described in 1887 by the famed Edward D. Cope, famous for his bitter rivalry with Othniel C. Marsh. Cope thought the remains were those of a new species in the genus Coelurus, but he would later recognize it as distinct. In 1889, he would re-describe it under the generic name Coelophysis, meaning “hollow form”, inspired by many of its bones being hollow. We know today that this was a common trait among some theropods. In the years to follow, Coelophysis would remain an obscure taxon. Then, in the 1940’s, an extensive Coelophysis bone bed was found at the Ghost Ranch site in New Mexico, containing the complete skeletons of many hundreds of individuals. So well preserved were these remains that one of the skeletons would later be made the new holotype for the genus. The creatures appear to have been caught in a flash flood by a stream or river, likely at the end of a long and severe drought.

Modern phylogenetic studies place Coelophysis within the clade Neotheropoda, occupying a status more basal than that of Dilophosaurus. It acts as the namesake of the superfamily Coelophysoidea and the family Coelophysidae. Procompsognathus and Megapnosaurus were close relatives. These animals were all lightly built, slender carnivores with semi-elongated necks and narrow skulls, their jaws lined by small, pointed teeth. Coelophysis mainly preyed on smaller reptiles or insects. It itself may’ve been prey for large non-dinosaurian predators like Postosuchus, a pseudosuchian distantly related to modern crocodiles. Both it and Coelophysis are known from the Chinle Formation, dated to the latter part of the Late Triassic. Early Jurassic-aged fossils from other regions, like those now referred to Africa’s Megapnosaurus, were once referred to Coelophysis. The discovery of so many specimens at Ghost Ranch may suggest it was a social animal, but we can’t be sure. Some bones of other animals found underneath some specimens were once seen as evidence that it cannibalized its own young when desperate, misinterpreted as being within the animal’s gut.