The rhynchocephalia (also known as the sphenodontida) or "beak headed" reptiles were once more common throughout the globe. Now though there is only one surviving family, the sphenodontidae. And of it, only one surviving genus: Sphenodon. The tuatara (spiny back).
Originally it was thought that there was only one species of tuatara, Sphenodon punctatus. That is until recently when genetic research showed that there is actually two different species both S.punctatus and S.guntherii.
Tuataras only live on the islands of New Zealand. Although they might superficially resemble lizards, tuataras are not in any lizard family. Rather, they come from a sister group to lizards and snakes. Some of the things that make tuataras different from lizards are their lack of external ears, a more formed parietal eye and a lack of hemipenes or even a penis in general.There are some things that tuataras share in common with lizards. The biggest one is caudal autotomy. That is the animals are able to drop their tails when danger threatens.
The two species of tuatara are listed below. Just click on the one you want to learn more about.