This page has been validated.
212
THE OSTEOLOGY OF THE REPTILES
- PARAPSIDA. A single temporal opening, between parietal and postorbito-squamosal arch; supratemporal (tabular) persistent. Ribs articulating more or less exclusively with centrum. A single coracoid.
- Proganosauria. Skeleton largely primitive. Aquatic, the neck and tail elongate. Phalangeal formula 2, 3, 4, 5, 4 (6). Skull imperfectly known; the quadrate fixed. Lower Permian.
- Ichthyosauria. Marine reptiles with short neck and all aquatic adaptations. Vertebrae amphicoelous; no dorsal intercentra. Quadrate fixed. Middle Triassic to Upper Cretaceous.
- Protorosauria. Aquatic or terrestrial. Not more than seven cervical vertebrae. Vertebrae amphicoelous (? Saphaeosauridae). Quadrate fixed. Phalangeal formula primitive. Lower Permian to Jurassic.
- Squamata. Quadrate freely articulated proximally (streptostylic) or secondarily fixed.
- Lacertilia (Sauria).[1] Parietals never united to basisphenoid by descending plates, the brain-case more or less membranous anteriorly.
- (a) Kionocrania. An epipterygoid present[2]; vertebrae amphicoelous with persistent dorsal intercentra, or procoelous and no dorsal intercentra; eight cervical vertebrae; limbed or limbless. Phalangeal formula primitive. Cretaceous to Recent.
- (b) Platynota. An epipterygoid. Vertebrae procoelous. Nine or more cervical vertebrae. Phalangeal formula primitive. Lower Cretaceous to Recent.
- (c) Pythonomorpha. Marine reptiles; limbs paddle-like, hyperphalangic; seven cervical vertebrae, procoelous; an epipterygoid present. Upper Cretaceous.
- (d) Amphisbaenia. No epipterygoid or temporal arch, the quadrate secondarily fixed; limbless or with vestigial front legs; vertebrae procoelous. Oligocene to Recent.
- (e) Rhiptoglossa. No epipterygoid or clavicles[3]; five cervical vertebrae; vertebrae procoelous; phalangeal formula 2, 3, 4, 4, 3. Oligocene to Recent.
- Ophidia (Serpentes). Brain-case enclosed by descending plates from parietals and frontals; no epipterygoids; no temporal arch; mandibles united by ligament. Vertebrae procoelous, with zygosphenes; no chevrons. Limbless. Cretaceous to Recent.
- Lacertilia (Sauria).[1] Parietals never united to basisphenoid by descending plates, the brain-case more or less membranous anteriorly.
- DIAPSIDA. Two temporal openings, separated by postorbito-squamosal arch; no supratemporals or tabulars (? Youngina). A