Page:The Osteology of the Reptiles.pdf/309

Rh.

Upper Jurassic. Dacosaurus Quenstedt, Geosaurus Cuvier, Europe. Metriorhynchus Quenstedt, Europe, Patagonia.

Lowermost Cretaceous. Neustosaurus Raspail, ? Enaliosuchus Dollo, Europe.

More or less upright-walking reptiles. The normal pubes and ischia meet in a ventral symphysis, the acetabulum perforated. No predentary or rostral bones. One or more antorbital openings. No dermal bones.

Carnivorous or secondarily herbivorous in habit. More or less bipedal in gait, the hind feet more or less digitigrade, the front legs more or less reduced. Pubes meeting in a long ventral symphysis, with a distal dilatation.

. Teeth less compressed, not recurved and somewhat thickened, their anterior and posterior borders denticulated. Anterior vertebrae platycoelous; twenty-three presacrals, three sacrals. Front legs a little longer than the femora, preaxonic, their phalangeal formula 2, 3, 4, 5, (?), the first claw large. Hind feet more mesaxonic, the first and fifth toes reduced. Feet digitigrade or semiplantigrade. Astragalus without ascending process.

Upper Triassic. Plateosaurus Meyer, Gressylosaurus Rütimeyer, Pachysaurus Huene, Teratosaurus Meyer, Europe. Euskelosaurus Huxley, Gryponyx Broom, South Africa.

This, the most primitive family of the Theropoda, is thought by some to have an ancestral relationship with the Sauropoda. The characters drawn chiefly from Plateosaurus may not and probably do not apply to all the genera listed in the family. The reptiles were clearly bipedal in gait, though of rather heavy build. Jaekel thinks that the hind feet were purely plantigrade, but this was improbable since the mesaxonic structure distinctly indicates the elevation of the ankle from the ground. Plateosaurus attained a length of about fifteen feet.