Sphenodontia: Sphenodontidae

1 or more robust "incisor" teeth forming chisel edge ankylosed to premaxilla; palatine dentition; marginal dentition acrodont or absent; shearing (not crushing or piercing) bite with simple orthal up-and-down) jaw motion; $ long thin posterior process of premaxilla excludes maxilla from margin of nares; $ lacrimal absent; may have dentine "lips"; $ antorbital skull very short (<25% of total skull); triradiate postfrontal broadly contacts frontal; complete lower temporal bar formed by jugal loosely contacting slim quadratojugal; $ dorsal process of jugal elongate; $ large (> 25% skull length) lower temporal fenestra; gap between jugal and quadratojugal small; proximal caudal vertebrae have large transverse processes; caudal autotomy septa may be present distally; humerus strongly bent and expanded at both ends; femur gently S-shaped.

short snout like Brachyrhinodon, multiple rows of teeth on the palate. It shows sphenodontian characters such as a groove between the maxilla and palatine for the dentary

Comments: Known from a partial skull and skeleton. The only known specimen went missing in the 1930s, but a number of casts and plaster moulds are available (Fraser & Benton 1989 p.416. )

small (c. 15 cm long), short-snouted skull with premaxillary beak. Benton 1985

Vertebrae amphicoelous, sometimes with persistent notochord; intercentra present in cervical (neck) and caudal (tail) regions. External nares separated ; interclavicle T-shaped; dermal scales subrectangular. Greatiy enlarged postfrontal bone extending far posteriorly (to the rear) on parietal. Except for a few teeth on the vomer in juveniles and the palatine row, all other palatal teeth absent (i.e. teeth on the roof of the mouth, in contrast to primitive amniotes). Premaxillae each with a small pointed tooth. A single series of enlarged, depressed, triangular, acrodont teeth present on maxillae, mandibles, and outer edge of the palatines; vomer toothless. pattern of tooth wear facets, tooth ultrastructure, and anteroposterior length of the mandibular articulation, all of which indicate development of the propalinal masticatory movements (front to rear chewing) as with the Recent Sphenodon Zittel/Eastman/Woodward 1902, Gauthier et al 1988 p.25

From Zittel/Eastman/Woodward 1902 (copyright expired): "Attaining a length of between 20 and 40 cm., and differing from the recent Sphenodon in that intercentra are absent between the dorsal vertebrae ribs without uncinate processes, and humerus not pierced by entepicondylar foramen. Mandibular rami united at the symphysis by ligaments ; second sacral rib bifid distally." applies also to Sapheosaurus and Kallimodon Gauthier et al 1988 p.26: Compared to sphenodontines and sapheosaurs, Homoeosaurus is distinguished by smaller size, gracile and elongate limbs, and a broad parietal table (skull roof above the orbits (eye holes)), all of which, with the possible exception of the limb proportions, are plesiomorphic (shared ancestral) features.