Microgomphodon

Microgomphodon is an extinct genus of therocephalian therapsid from the Middle Triassic of South Africa and Namibia. Currently only one species of "Microgomphodon", "M. oligocynus", is recognized. With fossils present in the "Cynognathus" Assemblage Zone (CAZ) of the Burgersdorp Formation in South Africa and Omingonde Formation of Namibia and ranging in age from late Olenekian to Anisian, it is one of the most geographically and temporally widespread therocephalian species. Moreover, its occurrence in the upper Omigonde Formation of Namibia makes "Microgomphodon" the latest-surviving therocephalian. "Microgomphodon" is a member of the family Bauriidae and a close relative of "Bauria", another South African bauriid from the CAZ. Like other bauriids, it possesses several mammal-like features such as a secondary palate and broad, molar-like postcanine teeth, all of which evolved independently from mammals.
Description.
"Microgomphodon" has a short snout and large eye sockets that are roughly equal in size to the temporal openings behind them (these openings are typically much larger in therocephalians). Its incisors are large and pointed, with the lower set splaying forward from the lower jaw. A pair of enlarged canines in the upper jaw separates the incisors in the front from the postcanines in the back. The postcanine teeth are widened and bear cusps that interlock with the postcanines of the lower jaw. They are positioned closer to the midlines of the upper and lower jaws than are the incisors due to an inward expansion of the maxilla and dentary bones.
"Microgomphodon" is very similar in appearance to "Bauria", but differs in having a small hole called a pineal foramen at the top of the skull behind the eye sockets, a complete postorbital bar enclosing the eye sockets from behind, fewer postcanine teeth, and canines located farther back along the upper jaw. Additionally, the two taxa can be distinguished by many subtle differences relating to the shape of the skull. For example, "Microgomphodon" has a deeper snout, slightly larger eyes, and a sharper angle to the zygomatic arches than does "Bauria". Specimens of "Microgomphodon" are generally smaller than those of "Bauria"; the largest skull of "Microgomphodon" is long whereas the largest of "Bauria" is .
Geographic and temporal distribution.
Most fossils of "Microgomphodon" come from the Karoo Basin of South Africa. Skulls of "Microgomphodon" have been found in two regions within the country: one southwest of Lesotho spanning the border between the Free State and the Eastern Cape and another northeast of Lesotho within the Free State near its border with KwaZulu-Natal. Fossil localities in the first region contain both "Microgomphodon" and "Bauria" remains, while localities in the second contain only "Microgomphodon". A skull of "Microgomphodon" has also been found in the upper Omingonde Formation in Namibia.
The oldest occurrence of "Microgomphodon" is in Subzone A of the "Cynognathus" Assemblage Zone, which dates to the Late Olenekian. "Microgomphodon" continues into Subzone B of the CAZ, which dates to the Anisian. The youngest known specimen of "Microgomphodon" is the skull from Namibia, found in the upper part of the Omingonde Formation near its contact with the overlying Etjo Formation. The specimen is not only the youngest of "Microgomphodon" but the youngest of any therocephalian, making "Microgomphodon" the latest-surviving member of the group.