Of the many mammal-like reptiles (see synapsida) recorded from the Triassic, this species is one of the closest to mammalian ancestry. It is assigned to the Ictidosauria and is characterized by a number of advanced cranial features. The skull of Diarthrognathus is only 4–5 cm long and its dentition is not as specialized as that of certain other mammal-like reptiles from the Upper Triassic.