As "Eothyris parkeyi" have short face, the lower jaw does not have the slender build. Dentary, angular, and surangular are visible on the outer surface, and also, the lower edge of the splenial is visible in ventral view. The medial surface of the jaw is not visible. The teeth are pointed with slightly recurved. "Eothyris parkeyi" had about 14 or 15 teeth, depending on the disposition of the precanine. The premaxilla carried three not enlarged teeth. In "Eothyris parkeyi" due to shortness of the face there is no precanine maxillary teeth. this feature is more specialized than any known sphenacodont. Very enlarged pair of canines, giving the snout distinctly a swollen appearance immediately posterior to the external naris. The most significant feature of "Eothyris parkeyi" is probably the morphology of the maxilla, because of its unique dental pattern. The maxilla in "Eothyris parkeyi" is thin, elongate element with an abrupt dorsal expansion in the area of the primary canine pair.