Sphenodontidae

Sphenodontidae Temporal range:
Tuatara (Sphenodon punctatus)
Skeleton of Sphenofontis, a sphenodontine from the Late Jurassic of Germany
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Rhynchocephalia
Suborder:	Sphenodontia
Family:	Sphenodontidae Cope, 1870 (conserved name)
Type species
Hatteria punctata Gray, 1842
Subgroups
†Eilenodontinae? †Opisthias? †Trullidens? †Ankylosphenodon? †Derasmosaurus? †Pamizinsaurus †Zapatadon Sphenodontinae †Sphenovipera †Cynosphenodon †Tika †Sphenofontis †Navajosphenodon †Kawasphenodon Sphenodon (tuatara)
Synonyms
Hatteriidae Cope, 1864 (rejected name) Rhynchocephalidae Hoffmann, 1881 (rejected name)

Skeleton of Navajosphenodon from the Early Jurassic of North America, one of the oldest sphenodontines.

Illustration of the skull of Navajospenodon in lateral view, showing closed temporal bar (bottom right)

Sphenodontidae is a family within the reptile group Rhynchocephalia, comprising taxa most closely related to the living tuatara of the genus Sphenodon. Historically the taxa included within Sphenodontidae have varied greatly between analyses, and the group has lacked a formal definition. Cynosphenodon from the Early Jurassic of Mexico has consistently been recovered as a close relative of the tuatara in most analyses, with the clade containing the two often called Sphenodontinae. The herbivorous Eilenodontinae, otherwise considered part of Opisthodontia, is also sometimes considered part of this family as a sister group to the remaining Sphenodontinae. Sphenodontines first appeared during the Early Jurassic, and are characterised by a complete lower temporal bar caused by the fusion of the quadrate/quadratojugal and the jugal, which was an adaption for reducing stress in the skull during hard biting. Like modern tuatara, members of Sphenodontinae were likely generalists with a carnivorous/insectivorous diet.