Full reference: E. D. Cope. 1878. Descriptions of extinct Batrachia and Reptilia from the Permian formations of Texas. Proceedings of the American Philosophical Society 17:505-530
Parent taxon: Synapsida according to W. Langston and R. R. Reisz 1981
See also Baur 1887, Berman 1977, Carroll 1988, Case 1907, Cope 1878, Currie 1977, Daly 1973, Eberth and Brinkman 1983, Gadow 1898, Haubold 1971, Haubold 1974, Haughton and Brink 1954, Hay 1902, Hay 1930, Huene 1954, Jaekel 1911, Kuhn 1946, Kuhn 1966, Langston 1965, Lewis and Vaughn 1965, Nopcsa 1923, Nopcsa 1928, Olson 1962, Olson 1966, Olson and Barghusen 1962, Olson and Beerbower 1953, Osborn 1903, Osborn 1903, Osborn 1904, Perrier 1928, Romer and Price 1940, Roxo 1937, Swinton 1934 and Zittel 1890
Sister taxa: Asaphestera, Caseasauria, Chelichnopodidae, Eupelycosauria, Ophiacomorpha
Subtaxa: Caseamorpha Echinerpeton Edaphosauria Lupeosaurus Milosaurus Nitosaurus Ophiacodontia Protoclepsydrops Xyrospondylus