One of the two surviving orders of lepidosaurian reptiles; they are represented today, however, by a single species, Sphenodon punctatus. They have a typical diapsid skull, and, also typically, the teeth are fused to the edges of the jaws; their only characteristic specialization is that the upper jaw forms an overhanging beak.
Sphenodon punctatus, the tuatara, is a moderate-sized (about 2–2½ ft or 0.6– 0.8 m long) lizardlike reptile which is strictly conserved on a few small islands off the coast of New Zealand. It formerly inhabited the mainland but was hunted to extinction by humans. Among living reptiles the tuatara is unique in having no penis; its “pineal eye,” however, is neither unique nor as functional as popularly supposed. By day it lives in shallow burrows, often in association with petrels; at night it emerges to feed on land snails and insects, especially crickets. Courtship behavior terminates with mating (fertilization is internal, despite the lack of penis in the male), after which the female leaves the male and buries her small leathery eggs in a burrow to incubate for 12–13 months. See also Lepidosauria; Reptilia.
