Daeodon

Daeodon (from Greek, daios "hostile", "dreadful" and odon "teeth") is an extinct genus of entelodont artiodactyl that inhabited North America between 29 to 19 million years ago during the late Oligocene and early Miocene epochs. The type species is Daeodon shoshonensis, the last and largest of the entelodonts, known adults of this species possess skulls about 90 cm (3 ft) in length. It had a broad distribution across the United States but it was never abundant.

Etymology
Although not specified in Cope's original description, the name Daeodon comes from the Greek words daios, meaning "hostile" or "dreadful" and odon, meaning "teeth".

Classification
The genus Daeodon was erected by the American anatomist and paleontologist Edward Drinker Cope in 1878, he classified it as a perissodactyl and thought it was closeley related to "Menodus".[2] This classification persisted until the description of "Elotherium" calkinsi in 1905,[3] a very similar and much more complete animal from the same rocks which was promptly assigned as a species of Daeodon by Peterson (1909)[4] which lead to its reclassification as a member of the family Entelodontidae. The exact relationships between Daeodon and other entelodonts are not well understood, some authors (Lucas et al., 1998) consider the greater morphological similarity of Daeodon to Paraentelodon rather than to earlier North American entelodonts like Archaeotherium as evidence for Daeodon being descendent from a Late Oligocene immigration of large Asian entelodonts to North America,[5] however, the existence of distinct specimens of Archaeotherium showing characters reminiscent of those present in both Paraentelodon and Daeodon rises the possibility of both genera being actually descendant from a North American common ancestor.

Species
The type species of Daeodon is D. shohonensis, based on a fragment of a lower jaw from the John Day Formation of Oregon. Several other species were assigned to the genus in the subsequent decades, like D. calkinsi, D. mento [8] and D. minor .[9] Since 1945 it had been suggested that two other taxa were actually junior synonyms of Daeodon[10] but the formalization of this referral didn't took place until the work of Lucas et al. (1998).[5] Ammodon leidyanum, named by Cope's rival, O. C. Marsh, and Dinohyus hollandi,[11] a complete skeleton from the Agate Springs quarry of Nebraska,[12] were found to be indistinguishable from each other and in turn both were indistinguishable from D. shoshonensis. [5] The other previously recognized species of Daeodon were also synonymized to D. shoshonensis[5] with the exception of D. calkinsi which was tentatively excluded from Daeodon. That same year, an obscure entelodont, Boochoerus humerosum was also synonymized to Daeodon by Foss and Fremd (1998) and albeit its status as a distinct species was retained they note that the differences could still be attributed to individual or population variation or sexual dimorphism.