Each of these species are considered nomen dubia today and based upon specimens belonging to two separate families of therocephalians.

[1][2][3][4] Scymnosaurus is estimated to have been approximately the size of the modern day hyena, and possessed teeth suggesting that it was carnivorous.

[1][5][6] It is notable that throughout the 19th century, Broom was involved with the work done with therocephalians and their classifications, and re-classifications, with paper and book publications ranging from 1903 to 1950.

[5] Later Scymnosaurus fossils have been recovered and recorded as coming from the Tapinocephalus Assemblage Zone, many specifically from the Beaufort Group in South Africa.

[7] The Tapinocephalus Assemblage Zone where Scymnosaurus fossils and other therapsids are found is the thickest layer of the Beaufort group.

Chemical analyses of the sediment in the Beaufort group suggests that the climate changed from glacial to post-glacial in the Early Permian, creating a marine environment in the Karoo Basin.

[8] In his 1903 publication, Broom argued for the establishment of a new taxon, Therocephalia, based on the palatal differences with Therapsida of three similar genera, Scylacosaurus, Ictidosaurus and Scymnosaurus.

The higher metabolic load associated with endothermy is associated with characters such as fur, increased aerobic capacity and the development of a secondary palate, which allows for airflow independent of oral food processing.

[10] It is, however, still unclear as to the order acquired characters that allowed the development of faster metabolisms, which happened at least twice with birds and mammals.

S. major is possibly the largest Therocephalian, as there is enough of its skull preserved to give a measurement of 210 mm (8.3 in) for preorbital length.