Rhynchocephalia (/ˌrɪŋkoʊsɪˈfeɪliə/, 'beak-heads') is an order of lizard-like reptiles that includes only one living species, the tuatara (Sphenodon punctatus) of New Zealand. Despite its current lack of diversity, during the Mesozoic the Rhynchocephalia included a wide array of genera within multiple (now extinct) lineages. The oldest record of the group is dated to the Middle Triassic around 238 to 240 million years ago, and they had achieved a worldwide distribution by the Early Jurassic. Most rhynchocephalians belong to the group Sphenodontia ('wedge-teeth'), which are characterized by a hooked beak-like structure at the tip of the snout formed by enlarged premaxillary teeth. Their closest living relatives are lizards and snakes in the order Squamata.