''Planocephalosaurus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

of rhynchocephalian. Fossils of the genus were found in the

Tecovas Formation The Tecovas Formation is a geological formation in Texas.Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Triassic, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berk ...

of Texas and the Magnesian Conglomerate of England. ''Planocephalosaurus'' was one of the first sphenodonts and bore a strong resemblance to the extant

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 ...

, albeit much smaller, at only in length. The creature is presumed to have fed on large

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s and small

vertebrate Vertebrates () comprise all animal taxon, taxa within the subphylum Vertebrata () (chordates with vertebral column, backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the ...

Dentition

''Planocephalosaurus'' exhibits very interesting dentition. Initially, it was believed to have been attached to the bone via

acrodont Acrodonty (from Greek ''akros'' 'highest' + ''dont'' 'tooth') is an anatomical placement of the teeth at the summit of the alveolar ridge of the jaw, without sockets, characteristic of bony fish. Functionally, acrodont tooth implantation may be rela ...

tooth implantation, however, after this specimen was exposed to X-radiography it was determined that this animal has a combination of different tooth implantation types. Similar to another rhynchocephalian, ''

Diphydontosaurus ''Diphydontosaurus'' is an extinct genus of rhynchocephalian reptile from the Late Triassic of England and Italy. This small animal was related to the living tuatara (''Sphenodon''). It may have grown to a length of . It is more derived than ' ...

'', it possesses acrodont teeth in the posterior portion of the jaw, and

pleurodont Pleurodont is a form of tooth implantation common in reptiles of the order Squamata, as well as in at least one temnospondyl. The labial (cheek) side of pleurodont teeth are fused (ankylosed) to the inner surface of the jaw bones The jaw is an ...

dentition in the anterior portion. ''Planocephalosauruss teeth were also fused with the cartilage, unlike its only

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...

relative the tuatara.

References

Triassic lepidosaurs Sphenodontia Late Triassic reptiles of Europe Prehistoric reptile genera {{triassic-reptile-stub