Bolosauridae is an extinct family of herbivorous, lizard-like reptiles known from the latest Carboniferous (Gzhelian) or earliest Permian (Asselian) to the early Guadalupian epoch (latest Roadian stage) of North America, China, Germany, Russia and France.
Description
Bolosaurids were small and superficially lizard-like. They are united by a number of morphological features including the palatal teeth on the roof of the mouth being highly reduced or entirely absent, a reduced transverse flange on the pterygoid bone of the skull that lies at the same level as the palate, and the alveolar shelf on the lower jaw is expanded downwards (ventrally) such that it almost reaches the bottom of the mandible, with this extension largely covered by a forward (anterior) extension of the prearticular bone. They are also noted for their distinct heterodont teeth, with the front teeth having a pointed incisiform-like morphology, while the back teeth are molar-like, with rounded cusps, suggesting that bolosaurids were herbivores, likely consuming high-fiber vegetation, which was likely extensively processed in the mouth prior to swallowing. These teeth had a thecodont (or anklyothecodont The molariform teeth, at least in Belebey show the deposition of tertiary dentine as response to wear, unlike most reptiles but similar to mammalian teeth, which likely served to enhance their longevity to compensate for their highly abrasive diet.
Taxonomy
Three genera of bolosaurid are currently recognised, Eudibamus, which only contains the type species E. cursoris, Bolosaurus with two species, and Belebey with five species, though not all of these species may be valid.
Davletkulia gigantea, initially described as a bolosaurid, was later reinterpreted as a tapinocephaloid dinocephalian.
Bolosaurids are traditionally considered "parareptiles", a large, historically thought to be a monophyletic clade also including other groups of primitive, largely Carboniferous-Permian reptiles, such as the mesosaurs, pareiasaurs, acleistorhinids, millerettids and procolophonoids. However, the monophyly of "Parareptilia" has subsequently come into question. Bolosauridae has also sometimes been considered part of the broader group "Bolosauria" alongside Erpetonyx from the Late Carboniferous of Canada, which is suggested to have been carnivorous rather than herbivorous like the bolosaurids. However, other studies have suggested that Erpetonyx is unrelated to bolosaurids.