TUATARA

lizardlike animal (Sphenodon punctatus), the sole living member of the reptilian order Rhynchocephalia. Structurally, the tuatara is not much different from related forms, also assigned to the order Rhynchocephalia, that may have appeared as early as the Lower Triassic Period (more than 200,000,000 years ago). Until recently the tuatara lived on the two main islands of New Zealand. Today, it is found only on certain islets in Cook Strait between the main islands and on islets between East Cape and North Cape of the North Island of New Zealand. (genus Sphenodon), either of two species of lizardlike animals that are the sole living members of the reptilian order Rhynchocephalia. They are found only on some of the islets of New Zealand. Tuataras attain lengths of about 70 cm (about 28 inches) and weigh up to 1 kg (2.2 pounds). A tuatara has two pairs of well-developed limbs and a scaly crest down the neck and back. Unlike lizards, it has a third eyelid, the nictitating membrane, which closes horizontally, and a pineal eye, an organ of doubtful function between the two normal eyes. The tuatara also has a bony arch, low on the skull behind the eyes, that is formed by the presence of two large openings (temporal fossae) in the region of the temple. It is this bony arch, which is not found in lizards, that has been cited as evidence that tuataras are survivors of the otherwise extinct order Rhynchocephalia and are not lizards. And indeed, tuataras differ little from the closely related form Homeosaurus, which lived 150 million years ago during the Jurassic Period. The tuatara was long thought to be a single species, S. punctatus, but authorities now acknowledge the existence of both it and another species that closely resembles it, S. guntheri. Tuataras are active at night, live in burrows, and eat insects, other small animals, and birds' eggs. They do well at relatively low temperatures. Eight to 15 eggs are laid in the spring, some distance from the burrow; hatching does not occur until the next spring. Some tuataras may live about 100 years. Additional reading W.H. Dawbin, The Tuatara in Its Natural Habitat, Endeavour, 21:1624 (1962), a review of distribution, life cycle, and ecology; A. Gunther, Contribution to the Anatomy of Hatteria (Rhynchocephalus, Owen.), Phil. Trans. R. Soc., 157:595629 (1867), the original detailed description of skeleton, muscles, externals, and classification; A.S. Romer, Osteology of the Reptiles (1956), sections on musculature, the brain, and the circulatory system, as well as osteology and relationships; Richard Sharell, The Tuatara, Lizards and Frogs of New Zealand (1966, reprinted 1975), a popular account of the natural history of the tuatara.