Dimacrodon

Dimacrodon is an extinct genus of non-mammalian synapsid from the latest Early Permian San Angelo Formation of Texas. It is distinguished by toothless, possibly beaked jaw tips, large lower canines and a thin bony crest on top of its head. Previously thought to be an anomodont therapsid related to dicynodonts, it was later found to lack any diagnostic features of anomodonts or even therapsids and instead appears to be a 'pelycosaur'-grade synapsid of uncertain classification.

== Description == Three specimens of D. hottoni are known, although they only comprise incomplete portions of the lower jaw and skull. The holotype specimen consists of a single partial mandible with teeth. The jaw is long with an unusually broad and deep mandibular symphysis, while the jaw rami are slender (although the additional material from D. sp. below suggests that the back of the jaws was also deeper). Unusually, the front of the jaw is toothless and has a rough bone texture, possibly supporting a beak like in dicynodonts, with no pre-canine teeth. Behind the toothless region is a single pair of large caniniforms, while the teeth behind them are much smaller and uniform in size, unlike typical 'pelycosaur' dentition (although see the edaphosaurid Gordodon), and are thecodont like the teeth of therapsids.