Rhynchocephalia (‘beak-heads’, rhynchocephalians; class Reptilia) Order of primitive, lizard-like reptiles dating from the Triassic and often cited as a living fossil. The order contains only one species, Sphenodon punctatus, the tuatara of New Zealand. This survives only in the Bay of Plenty, and it has protected status. The skull is of the primitive diapsid type, with a fixed quadrate bone. The teeth are fused to the edge of the jaw (acrodont), with a tendency to develop a beak-like structure anteriorly.

Rhynchocephalia (‘beak-heads’, rhynchocephalians; class Reptilia, subclass Lepidosauria) An order of primitive, lizard-like reptiles, dating from the Triassic, that contains only one family, the Sphenodontidae, comprising one species, Sphenodon punctatus, the tuatara of New Zealand.