Studies of the casts of Stegomosuchus, a small reptile from the Upper Trias of the Connecticut Valley, hitherto regarded as a pseudosuchian thecodont, suggests that the skull of Protosuchus includes two pairs of supraorbital bones, and as a consequence the narrow interorbital region indicates a closer relationship to the South African genus Notochampsa than has previously been thought. These three genera of Late Triassic crocodilians are placed in the family Stegomosuchidae von Huene, 1922. Proterochampsa, from the Ischigualasto Formation of Argentina, described by Reig (1959) and Sill (1967) as an ancestral crocodile, is considered to be an extremely primitive phytosaur.