New specimens of Stenocybus acidentatus (Therapsida: Dinocephalia) from the Middle Permian Dashankou Fauna of China
Authors:
Jiang et al
Abstract:
The basal dinocephalian clade Stenocybusidae was known from two incomplete specimens representing one generus, Stenocybus, from Dashankou fanua in Yumen, Gansu Province of China. The holotype of Stenocybus acidentatus is laterally compressed, making some characters unclear. Here we describe two new specimens of Stenocybus acidentatus from the same locality, an anterior portion of skull with articulated jaws, and a right dentary with nearly complete dentition. They show some detailed features on the morphology of the premaxilla, maxilla, nasal, external nares and dentary. The phylogenetic relationship between Stenocybus acidentatus and the relatively large Sinophoneus yumenensis is still difficult to determine, and needs more new complete material and further evidences.
Osteology, ontogeny, and phylogenetic position of Sinophoneus yumenensis (Therapsida, Dinocephalia) from the Middle Permian Dashankou Fauna of China
Author:
Jun Liu
Abstract:
Sinophoneus yumenensis and Stenocybus acidentatus are the only dinocephalians from China, and the latter taxon has been proposed to be a junior synonym of the former. Here I confirm this synonymy on the grounds that the differences between the two putative taxa are due to ontogenetic variation. The osteology of Sinophoneus yumenensis is described in detail based on both previously described specimens and several new ones from the same locality. Sinophoneus yumenensis differs from all other anteosaurs in having premaxillary dorsal processes that are separated by relatively long nasal anteromedial processes, and vomers without raised, elongated edges; from all other anteosaurs except Archaeosyodon praeventor in having distinct frontal posterolateral processes, and a wide intertemporal region formed partly by long posterior processes of the postfrontals that approach the posterior edge of the skull roof; and from Archaeosyodon praeventor in having a well-developed midline ridge on skull roof. A revised phylogenetic analysis including the new material recovers Sinophoneus as the most basal known anteosaurid.
