The skull of "Sphenacodon" is very similar to that of "Dimetrodon". It is narrow from side to side and vertically deep, with an indented notch at the front of the maxillary bone in the upper jaw. The upper and lower jaws are equipped with an array of powerful teeth, divided into sharp pointed "incisors" large stabbing "canines" [caniniforms, and smaller slicing back teeth . The orbit is set high and far back with a single opening (temporal fenestra) behind and partly below the eye, a characteristic of synapsids.