Planocephalosaurus

Planocephalosaurus is an extinct genus of basal rhynchocephalian. Fossils of the genus are primarily known from fissure fill deposits from the Late Triassic of southwest Britain, with fragmentary remains possibly belonging to the genus also known from the Late Triassic of Texas.

== Taxonomy == The genus and the type species P. robinsonae was described in 1982 by Fraser from remains found in fissure fill deposits in Gloucestershire in southwest Britain. In 2004, a second species P. lucasi was described from remains found in the Tecovas Formation in Texas. P. robinsonae is known from disarticulated remains covering most of the skeleton,, while P. lucasi is known from fragments of the jaws. While originally classified in Sphenodontidae, later studies have placed it as a basal sphenodontian, more derived than Diphydontosaurus but more basal than Clevosaurus.