Coelophysis ( /ˌsɛlɵˈfaɪsɨs/ or /ˌsiːlɵˈfaɪsɨs/), meaning "hollow form" in reference to its hollow bones (Greek
κοιλος/koilos meaning 'hollow' and φυσις/physis meaning 'form'), is one of the earliest known genera of dinosaur. It was a small, carnivorous biped that lived during the Late Triassic(Norian stage) of the southwestern United States, with scattered material representing similar animals to Coelophysis found worldwide in some Late Triassic and Early Jurassic formations.The type species, C. bauri, was described by Edward Drinker Cope in 1889. The name Rioarribasaurus is synonymous with Coelophysis. Another dinosaur, Megapnosaurus, is also often considered synonymous with Coelophysis.