Tuatara. 1896 engraving of a tuatara, a rare species of reptile sometimes called a insliving fossilins. The tuatara (Sphenodon punctatus) is the only surviving species of the Rhynchocephalia, an ancient order of reptiles that was widespread in the era of the dinosaurs. Fossil evidence suggests that the tuatara's basic body plan has remained unchanged for 200 million years. The species is restricted to a few tiny islands near mainland New Zealand. Adults measure up to 65cm in length and are most active at twilight or night, feeding on insects, worms and snails. With an optimum body temperature of only 12 degrees C the tuatara has the lowest requirement for warmth of all reptiles.