Dicynodon bainii

Aulacephalodon Temporal range: Permian 299–252 Ma PreЄ Є O S D C P T J K Pg N
Skeleton of A. peavoti in the Field Museum of Natural History
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Order:	Therapsida
Infraorder:	†Dicynodontia
Family:	†Geikiidae
Genus:	†Aulacephalodon Seeley, 1898
Type species
Aulacephalodon bainii Seeley, 1898 (type)
Species
†A. bainii Seeley, 1898 †?A. peavoti Broom, 1921
Synonyms
†Dicynodon bainii Owen, 1844 †Dicynodon tigriceps Owen, 1844 †Dicynodon laticeps Broom, 1912 †Bainia peavoti Broom, 1921 †Bainia haughtoni Broom, 1921 †A. latissimus Broom, 1932 †A. nesamanni Broom, 1936 †A. nodosus Van Hoepen, 1934 †A. luckhoffi Broom, 1937 †A. hartzenbergi Broom, 1937 †A. coatoni Broom, 1941 †A. brodiei Broom, 1941 †A. cadlei Broom, 1948 †A. pricei Broom and George, 1950 †A. vanderhorsti Broom and George, 1950

Aulacephalodon is an extinct genus of medium-sized dicynodonts, or non-mammalian synapsids, that lived during Permian period, about 299-252 million years ago. Individuals of Aulacephalodon are commonly found in the Lower Beaufort Group of the Karoo Supergroup of South Africa and Zambia. Rising to dominance during the Late Permian, Aulacephalodon were the dominant terrestrial vertebrate herbivores until they became extinct during the Triassic. No living relatives of Aulacephalodon exist today. Two species have been named, the type species, A. bainii, and a second species, A. peavoti. However, debate exists among paleontologists if A. peavoti is a true member of the genus Aulacephalodon. Therefore, a majority of the information known about Aulacephalodon is in reference to discoveries about A. bainii.

The name Aulacephalodon combines the Greek words aulak- (aulax), meaning "a furrow", kephale, meaning "head," and odon, meaning tooth. Together, Aulacephalodon means "furrow-head tooth." The species Aulacephalodon bainii was named in honor of Andrew Geddes Bain (1797-1864), a Scottish geologist and road engineer who is credited with discovering the first dicynodont skull in South Africa.

Aulacephalodon belong to the family Geikiidae, a family of dicynodonts generally characterized by their short, broad skulls and large nasal bosses. Two autamorphies used to define Geikiidae include (1) the posterior portion of the zygomatic arch thickened and/or downturned; (2) the labial fossa present. Both features are found in Aulacephalodon and allow for suggestions to be made about possible sexual dimorphism evident in A. bainii.

Among certain anomodont therapsids, Aulacephalodon and Pelanomodon are distinguished from their related genera, Oudenodon and Rhachiocephalus by the specialization of their biting mechanism and the relative size of their nasal and prefrontal bosses.Aulacephalodon and Pelanomodon bit using the transverse anterior tips of the jaws, while Oudenodon and Rhachiocephalus bit using the sides of their horn covered jaws. The difference in jaw morphology between the two groups of genera is a notable dichotomy among these related therapsids. Aulacephalodon was unique among dicynodonts and its related therapsids because members of this genus were one of the only dicynodonts to possess canine tusks.