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.