Akidnognathidae
Akidnognathidae is an extinct family of therocephalian therapsids from the Late Permian and Early Triassic of South Africa, Russia and China. The family includes many large-bodied therocephalians that were probably carnivorous, including "Moschorhinus" and "Olivierosuchus". One akidnognathid, "Euchambersia", may even have been venomous. Akidnognathids have robust skulls with a pair of large caniniform teeth in their upper jaws. The family is morphologically intermediate between the more basal therocephalian group Scylacosauridae and the more derived group Baurioidea. Classification. History. The first family-level name used to classify an akidnognathid was Euchambersidae, erected by South African paleontologist Lieuwe Dirk Boonstra  in 1934, in reference for the genus "Euchambersia", which is possibly one of the oldest known venomous tetrapods. In 1940, German paleontologist Friedrich von Huene changed the spelling of the name to Euchambersiidae, the correct form of Latin. Akidnognathidae was first named in 1954 by South African paleontologists Sidney H. Haughton and A. S. Brink. It included several therocephalians still recognized as akidnognathids as well as several now classified as scylacosaurids. English and American paleontologists D. M. S. Watson and Alfred Romer moved many of these therocephalians into the family Whaitsiidae in 1956, although many were moved back to Akidnognathidae  in later years. Whaitsiids and akidnognathids are similar in appearance, leading some paleontologists to propose placing them in a superfamily called Whaitsioidea. Moschorhinidae was erected as another name for the family in 1974, and Annatherapsididae was proposed in 1975. Three subfamilies were also proposed in 1975: Annatherapsidinae, Moschorhininae and Euchambersiinae. While the name Euchambersiidae may have priority over Akidnognathidae because it was named first, Akidnognathidae is currently considered the valid name because it is based on the first named genus of the group, "Akidnognathus" ("Akidnognathus" was named in 1918 while "Euchambersia" was named in 1931). Phylogeny. Topology recovered by the  2016 analysis of Huttenlocker "et al." is showed below.