THE SUBCLASS DIAPSIDA 29 1 



Family Metriorhynchidae, 



Upper Jurassic. Dacosaurus Quenstedt, Geosaurus Cuvier, 

 Europe. Melriorhynchus Quenstedt, Europe, Patagonia. 



Lowermost Cretaceous. Neustosaurns Raspail, ? Enaliosuchus 

 Dollo, Europe. 



[DINOSAURIA] 



17. ORDER SAURISCHIA 



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. 



A. Suborder Theropoda 



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. 



Family Plateosauridae. Teeth less compressed, not recurved 

 and somewhat thickened, their anterior and posterior borders den- 

 ticulated. 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 digiti- 

 grade or semiplantigrade. Astragalus without ascending process. 



Upper Triassic. Plateosaurus Meyer, Gressylosaurus Riitimeyer, 

 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. 



