A new specimen of Hesperosuchus agilis from the Upper Triassic of New Mexico and the interrelationships of basal crocodylomorph archosaurs

An articulated partial skeleton, including a nearly complete skull and left forelimb, of a crocodylomorph reptile from the Upper Triassic Chinle Forma tion of Ghost Ranch. New Mexico. is referable to Hesperosuchus agilis Colbe rt, 1952. It contributes much new information on the skeletal structure of this previously poorly known taxon. A large, circular palpebral bone is pre sent in each orbit. The quadratojugal is particularly well preserved and su ggests a reinterpretation of this element in related taxa including Sphenos uchus. Previous analyses of sphenosuchian relationships reached conflicting results, and a critical review of the characters used in these analyses is presented. A phylogenetic analysis of basal crocodylomorph taxa provides w eak support for sphenosuchian monophyly, placing Hesperosuchus with Saltopo suchus. Dibothrosuchus, and Sphenosuchus.