Sphenodon punctatus (Gray 1842- Hatteria punctata) extant - 80 cm in length, is an example of how long a particular genus can survive. Fossils of sister taxa are found in the Triassic, over 200 mya. Individuals may live over 100 years. Sphenodon was derived from a sister to Planocephalosaurus and phylogenetically preceded Brachyrhinodon.
Distinct from Planocephalosaurus, the skull of Sphenodon had a naris raised higher on the shortened rostrum. The postorbital portion of the skull was longer. A complete lower temporal bar was present. The upper temporal bar and parietals were considerably more gracile. The palatal teeth are restricted to lateral rows on the palatine and the interpterygoid fenestra is smaller.
The neural spines are all taller. The cervicals 4-8 have robust ribs with paddle tips. The dorsal ribs have uncineate processes. The caudals are relatively gracile with short chevrons.
The scapula is not fused to the coracoid. The clavicles and the transverse processes of the interclavicle are located a short distance anterior to the scapula and coracoid. Gastralia are present. The forelimbs are robust (Sphenodon can dig its own burrow). In contrast to preceding taxa, the ulna is bowed out and well separated from the radius, especially distally. Sphenodon provides a good example of a complete set of carpals. Of particular interest to pterosaur origins is the shape of the medial and lateral centralia.
The ilium is very tall and narrow and angled slightly posteriorly. The pubis and ischium are oriented chiefly medially. The hindlimbs are not robust. In contrast to preceding taxa, the fibula is bowed out and well separated from the tibia, especially distally. The tarsus elements are coosified. |
