Sphenodontidae is a family within the reptile group
Rhynchocephalia
Rhynchocephalia (; ) 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 rhynchocephalians were a diverse g ...
, comprising taxa most closely related to the living
tuatara
Tuatara (''Sphenodon punctatus'') are reptiles endemic to New Zealand. Despite their close resemblance to lizards, they are part of a distinct lineage, the order Rhynchocephalia. The name ''tuatara'' is derived from the Māori language and m ...
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
Opisthodontia is a proposed clade of sphenodontian reptiles, uniting ''Opisthias'' from the Late Jurassic-earliest Cretaceous of Europe and North America with the Elienodontinae, a group of herbivorous sphenodontians known from the Late Triassic ...
, otherwise considered part of
Opisthodontia, is also sometimes considered part of this family as the sister group to Sphenodontinae. Sphenodontines first appeared during the
Early Jurassic
The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...
, and are characterised by a complete lower temporal bar caused by the fusion of the
quadrate/
quadratojugal The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians.
Anatomy and function
In animals with a quadratojugal bone, it is typically found connected to the jugal (cheek) bone from the front and ...
and the
jugal
The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species.
Anatomy ...
, 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.
References
Sphenodontia
Taxa named by Edward Drinker Cope
Reptile families
Extant Early Jurassic first appearances
Toarcian first appearances
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