Aetosaurus is an extinct genus of archosaur reptile belonging to the aetosaur order. It is generally considered to be the most primitive aetosaur.[1] Three species are currently recognized: A. ferratus, the type species from Germany and Italy;[2] A. crassicauda from Germany;[3] and A. arcuatus from eastern North America. Additional specimens referred to Aetosaurus have been found from South Africa,[4] the Chinle Group of the southwestern United States,[5][6] and the Fleming Fjord Formation of Greenland.[7] Specimens of Aetosaurus occur in Norian-age. strata.