tuatara or tuatera, lizardlike reptile, Sphenodon punctatus, last survivor of the reptilian order Rhynchocephalia, which flourished in the early Mesozoic era before the rise of the dinosaurs. Also called sphenodon, it is found on a few islands off the New Zealand coast. The olive colored, yellow-speckled tuatara reaches a length of 2 ft (60 cm) or more. It is very lizardlike in external form, with a crest of spines down its neck and back. However, its internal anatomy, its scales, and the attachment of its teeth are quite different from those of lizards. Like certain lizards, it possesses a vestigial third eye (pineal eye) on top of its head, but this organ is probably not sensitive to light. Tuataras usually inhabit the breeding burrows of certain small petrels. They feed on small animals, especially insects, and reproduce by laying eggs. Tuataras lived on the mainland of New Zealand before the arrival of the Maoris but either were exterminated by hunting or died out as a result of the altered environment. Their survival on the offshore islands was threatened by the introduction of sheep, which altered the vegetation by grazing; however, they are now under strict government protection, and their numbers are increasing. Captive tuataras mature in about 20 years, and it appears that their life span may exceed a century. Tuataras are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Rhynchocephalia.

Either of two species (Sphenodon punctatus and S. guntheri) of lizardlike nocturnal reptiles of the order Sphenodontida, found on certain islets of New Zealand. Up to 2 ft. (60 cm) long and weighing over 2 lb (1 kg), tuataras have two pairs of well-developed limbs, a scaly crest down the neck and back, a third eyelid that closes horizontally, and a pineal eye between the two normal eyes. A bony arch behind the eyes distinguishes tuataras from lizards. They eat insects, other small animals, and birds' eggs. In the spring the females lay 8–15 eggs away from their burrow. Tuataras may live 60 years or more..

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