Page:The Osteology of the Reptiles.pdf/228



1. ANAPSIDA. Temporal region of skull roofed over, or secondarily emarginated, not perforated.

1. Cotylosauria. Skeleton primitive; two coracoids ; at least eighteen dorsal vertebrae, their ribs not expanded.

1. . Most primitive; teeth conical, in single row; intertemporal and otic notch. Insectivorous. Lower Permian.

2. . Teeth heterodont, the posterior transversely molariform, crushing. Malacophagous. Lower Permian.

3. . Teeth anisodont, in two or more rows posteriorly; no supratemporal; interparietal on posterior surface. Lower Permian.

4. . Teeth anisodont, conical, in single row; interparietal on dorsal surface. Tail long. Lower Permian.

5. [. Teeth blunt or pebble-like, in single rows in upper jaw and dentary, numerous on palate and coronoid; interparietals large on dorsal surface. Lower Permian.]

6. . Teeth anisodont, the posterior flattened [compressed] and crenulate; an acromion. Middle and Upper Permian.

7. . Incisors conical, posterior teeth transverse, crushing; no supratemporal; interparietal obsolete or absent. Triassic.

2. Eunotosauria. Skeleton primitive; two coracoids, ten dorsal vertebrae, their ribs expanded to meet on the dorsum, and a dermal layer of bony plates. Middle Permian.

3. Testudinata (Chelonia). Skeleton not primitive; a single coracoid; ten dorsal vertebrae, their ribs expanded to meet on the dorsum or a dermal layer of bony plates.

1. . No mesoplastra. Cervical vertebrae amphicoelous or concavo-convex, neck not retractile. Upper Triassic to Cretaceous.

2. . Neck retracted laterally; pelvis united with plastron. Jurassic to Recent.

3. . Neck retracted vertically; carapace with peripheral plates. Jurassic to Recent.

4. . Neck retracted vertically; no peripheral plates. River turtles. Cretaceous to Recent.