squamosal and postorbital are extensively in contact because the temporal opening is small and of oval shape. Also, because the cheek slants outward to very higher degree than is usual in pelycosaurs, the temporal opening is exposed in dorsal view. The premaxillae and nasals are short and the frontals are of moderate length. The supratemporal in Eothyris parkeyi is much more extremely developed than in any other pelycosaur. In Eothyris parkeyi, the postorbital bone is probably the largest for any synapsid, with large lateral and dorsal portions to the skull roof. The slope from skull table to quadrate is gentle, due to shortness of skull. The quadratojugal is very long and jaw articulation is in line with the tooth row. Typical pterygoid flanges and slender are present back in the skull, below the anterior part of the temporal opening. The quadrate is on the right side and is exposed dorsally. The interparietal and tabulars occupy the dorsal rim of the occipital surface. Teeth As Eothyris parkeyi has a short face, the lower jaw does not have a slender build. Dentary, angular, and surangular are visible on the outer surface, and also, the lower edge of the splenial is visible in the 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 are 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 a thin, elongate element with an abrupt dorsal expansion in the area of the primary canine pair. Classification Eothyris is classified in the monophyletic family Eothyrididae. It is one of two genera in the family, the other being Oedaleops. The family is grouped in Caseasauria, and only cranial remains are known from it. The family is greatly supported, with nine dental and cranial features. Below is the cladogram of the analysis of Reisz et al. (2009). Paleobiology The short face and dental structures represent an extreme type of development of predaceous