Two new archosaur reptiles from the late Triassic of Texas

Two new basal archosaurs, Pteromimus longicollis and Procoelosaurus brevicollis are described from the Tecovas Formation (late Carnian) and the Cooper Canyon Formation (early Norian) of west Texas, and a new family Pteromimidae is established to include the two taxa. Pteromimus is based on an incomplete skull and associated and isolated skull and vertebral elements. The skull is high, with narrow snout, large orbit and naris, pneumatized maxilla and premaxilla, vaulted frontal, short parietal, large plate-like supraoccipital, and reduced post-temporal openings. The dentition is thecodont and consists of conical teeth with fluted distal ends that are long and slightly recurved anteriorly and short, more laterally compressed teeth posteriorly. The vertebrae of both Pteromimus and Procoelosaurus are with procoelous and hollow centra, with large cavities for the interspinal ligament, well-developed epipophyses, long and low neural arches carrying long neural processes with spine tables. Pteromimus is distinguished by low neural processes with moderately developed spine tables and weakly developed ornamentation, while Procoelosaurus is characterized by a tall neural processes with greatly expanded spine tables with distinctive sculpturing. The cervical vertebrae are elongate, dorsoventrally compressed, and bear unusual apophyses consisting of a large posterior depression and a small anterior process formed by the thickened lateral edge of the centrum.; Procoelosaurus brevicollis is represented by associated vertebrae, pelvis, hindlimb and skull elements, along with numerous isolated vertebrae. The skull is high and has a broad triangular snout. The dentary has an unusual wide groove on the medial side. The numerous thecodont teeth are recurved, compressed, and with serrated posterior edge. The iliac blade is high, with enlarged anterior portion and long, tapering posterior end. The femur has well developed condyles, weakly developed lesser and fourth trochanters, and the head is at an obtuse angle. The foot is similar to that of early pterosaurs in that the mesotarsal ankle lacks astragalocalcaneal foramen, the fifth metatarsal is hooked, and metatarsals I–IV are closely appressed and subequal in length. New phylogenetic analyses of Archosauria that include morphometric characters indicate that Pteromimidae is the sister group of pterosaurs.