Tuatara

The tuatara is the only surviving member of the order Rhynchocephalia[?]. It is native to a small number of islands off New Zealand and has been classified as an endangered species since 1895.

Though it resembles a lizard, it has several characteristics unique among reptiles. Its teeth are fused to its jaw bone. It thrives in much lower temperatures than are tolerated by most reptiles, preferring temperatures of 60 to 70 degrees Fahrenheit (16-21 C); temperatures over 80 (27) degrees are fatal. It is extremely long-lived, with individuals commonly living for over a century, and reproduces very slowly: tuataras take at least ten years to reach sexual maturity, females only lay eggs once every four years, and it takes between 12 and 15 months after copulation for a new tuatara to hatch from its egg. Like some lizards, it has a third eye on the top of its head; in adult animals a scale grows over the eye, and its purpose isn't clear.

See also: Animal Diversity Web (http://animaldiversity.ummz.umich.edu/accounts/sphenodon/s._punctatus%24narrative)