Page:The Osteology of the Reptiles.pdf/231

single coracoid; no cleithrum. Phalangeal formula primitive. Often reduced postaxially.

12. ? Proterosuchia. Skull elongate, with palatal teeth; an antorbital vacuity. Skull only known. Triassic.
13. ? Eosuchia. No antorbital vacuity^[1]; interparietal and tabulars present; a parietal foramen. Only skull known. Upper Permian.

A. DIAPTOSAURIA. No antorbital foramen in skull; no supratemporal, tabulars or interparietals; palate with teeth. Vertebrae amphicoelous. Dorsal ribs articulating with intercentral space or centrum and arch, holocephalous.

14. Rhynchocephalia. Teeth protacrodont or acrodont.
    1. Rhynchosauria. Skull broad, with decurved premaxillae and crushing teeth on palate. No epicondylar foramina; pubo-ischiatic opening small. Littoral reptiles. Upper Triassic.
    2. Sphenodontia. Premaxillae beak-like; pelvis with large pubo-ischiatic vacuity; an entepicondylar foramen; dorsal intercentra persistent. Littoral reptiles. Upper Jurassic to Recent.
    3. Choristodera. Face elongate, the nares terminal; no pubo-ischiatic vacuity; teeth labyrinthine. Subaquatic. Uppermost Cretaceous and Lowermost Eocene.
    4. ? Thalattosauria. Skull elongate, with external nares posterior. Ribs attached by single head to centrum. Limbs paddle-like. Imperfectly known. Aquatic. Triassic.

AA. ARCHOSAURIA. Dorsal ribs, anteriorly at least, articulating with arch only, dichocephalous; no teeth on palate; no parietal foramen; no supratemporal, interparietal, or tabulars; vertebrae variable; dorsal intercentra not persistent; usually an antorbital opening. Typically with large pubo-ischiatic vacuity.

15. Parasuchia. Pelvis more or less plate-like with small pubo-ischiatic vacuity; vertebrae amphicoelous; no false palate; phalanges not reduced; body with dermal scutes.
    1. Pseudosuchia. External and internal nares near extremity of face; legs elongate, the epipodials long. Cursorial reptiles. Triassic.
    2. Pelycosimia. External and internal nares terminal. Legs short and stout. Terrestrial or marsh reptiles. Triassic.
    3. Phytosauria. External and internal nares remote from extremity of slender face. Triassic.
16. Crocodilia. Pubes excluded from acetabulum, not meeting in ventral symphysis. A secondary palate. External nares terminal; vertebrae amphicoelous or procoelous; postaxial digits reduced.
    1. Eusuchia. With dermal plates; no sclerotic plates. Amphibious. Jurassic to Recent.

1. [According to Broom, a well-preserved antorbital vacuity is present.—Ed.]