Sphenacodont

Sphenacodon is an extinct genus of synapsid that lived from about 300 to about 280 million years ago during the Late Carboniferous and Early Permian periods. Like the closely related Dimetrodon, Sphenacodon was a carnivorous member of the Eupelycosauria family Sphenacodontidae. However, Sphenacodon had a low crest along its back, formed from blade-like bones on its vertebrae instead of the tall dorsal sail found in Dimetrodon. Fossils of Sphenacodon are known from New Mexico and the Utah …

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", and smaller slicing back teeth. The orbit is set high and far back with a single opening behind and partly below the eye, a characteristic of synapsids.

The American paleontologist O.C. Marsh named Sphenacodon in 1878, based on part of a lower jaw bone found in the redbeds of northern New Mexico by fossil collector David Baldwin. In his very short description of the jaw, Marsh cited the back teeth as characteristic and assessed the animal as "about six feet in length, and  carnivorous in habit," although the rest of the skeleton was not known. He did not provide an illustration of the specimen. Marsh gave the genus the Latin specific name ferox."