Page:The Osteology of the Reptiles.pdf/232

214 ::1. . Neck shorter; no dermal plates; sclerotic plates in orbits. Vertebrae amphicoelous; a terminal caudal fin. Front legs reduced, paddle-like. Marine. Jurassic.


 * DINOSAURIA. More or less upright-walking reptiles.

1. Saurischia. Pelvis normal, the pubes meeting in a ventral symphysis; presacral vertebrae amphicoelous, or some or all opisthocoelous. No predentary or rostral bones in skull. Postaxial digits reduced. No dermal ossicles.

1. . Carnivorous or secondarily herbivorous, bipedal in gait, the front legs more or less reduced. Triassic to close of Cretaceous.

2. . Herbivorous, quadrupedal, the front legs but little or not at all reduced; limb bones not hollow; neck and tail elongate. Jurassic, Cretaceous.

2. Ornithischia (Orthopoda). Herbivorous, a predentary bone in mandible; pubes composed of a spatulate anterior process not meeting in symphysis, and a more or less elongate posterior process. Postaxial digits reduced.

1. . Upright-walking, bipedal. Without dermal bones. Lower Jurassic to close of Cretaceous.

2. . Quadrupedal, with dermal armor of plates and spines; skull small; bones solid. Jurassic to close of Cretaceous.

3. . Quadrupedal. Skull very large with bony horns and a posterior expansion fringed with scutes or spines. Uppermost Cretaceous.

3. Pterosauria. Volant reptiles, the bones pneumatic. Fourth finger greatly elongated to support patagium. Vertebrae procoelous.

1. . Wing metacarpal not longer than forearm; tail long. Skull with teeth. Jurassic.

2. . Wing metacarpal longer than forearm; tail short. Skull with or without teeth. Upper Jurassic to Upper Cretaceous.