Poposaurus

Poposaurus Temporal range: Late Triassic (Norian), 216 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Illustration of UR 357, the holotype specimen of Poposaurus gracilis (1915) in the collections of Field Museum.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauria
Clade:	Pseudosuchia
Clade:	†Poposauroidea
Family:	†Poposauridae
Genus:	†Poposaurus Mehl, 1915
Species
†P. gracilis Mehl, 1915 (type) †P. langstoni (Long and Murry, 1995 [originally Lythrosuchus langstoni])
Synonyms
Lythrosuchus Long and Murry, 1995

Poposaurus is an extinct genus of pseudosuchian archosaur from the Late Triassic of the southwestern United States. It belongs to the clade Poposauroidea, an unusual group of Triassic pseudosuchians that includes sail-backed, beaked, and aquatic forms. Fossils have been found in Wyoming, Utah, Arizona, and Texas. Except for the skull, most parts of the skeleton are known. The type species, P. gracilis, was described and named by Maurice Goldsmith Mehl in 1915. A second species, P. langstoni, was originally the type species of the genus Lythrosuchus. Since it was first described, Poposaurus has been variously classified as a dinosaur, a phytosaur, and a "rauisuchian".

Like theropod dinosaurs, Poposaurus was an obligate biped, meaning that it walked on two legs rather than four. However, as a pseudosuchian, it is more closely related to living crocodilians than to dinosaurs.^[1] Poposaurus is thought to have evolved this form of locomotion independently, possibly from early archosaurs' ability to high walk.