Stenocybus accidentusis (Cheng and Li 1997) IGCAGS V 361 Early Permian ~295 mya is the most primitive anomodont therapsid in the lineage of the dicynodonts like Dicynodon and dromasaurs like Galechirus. Derived from a sister to Cutleria, Stenocybus the genus is known from a complete skull and a few bits and pieces of the skull of a second individual. Originally considered a basal dinocephalian (therapsid), a later report by Kammerer (2010) considered it a juvenile Sinophoneus, an anteosaur. Hipposaurus is a sister in the lineage of Kynodontia that led to mammals and humans.
In primitive synapsids the lacrimal contacts the naris. In derived synapsids and all therapsids, the maxilla expands dorsally covering the lacrimal. Earlier I wondered if the lacrimal was the external septomaxilla. The septomaxilla is traditionally a bone inside the naris. In Stenocybus the anterior tip of the lacrimal and the septomaxilla are both present. Part of the broken maxilla exposes the underlying lacrimal.
First Appearance of the Preparietal
Stenocybus has a small new medial bone anterior to the parietal foramen, the preparietal, only seen in anomodonts and, by convergence, in Gorgonopsia.