Andrewsarchus

Andrewsarchus mongoliensis (/ˌændruːˈsɑrkəs/ AN-drew-SAR-kəs; Andrews + Greek: ἀρχός, "ruler"), is an extinct mammal that lived during the Eocene epoch, roughly between 45 and 36 million years ago. It had a long snout with large, sharp teeth and flat cheek teeth that may have been used to crush bones. Because Andrewsarchus is only known from a single skull, whether it was an active predator or a large scavenger is open to debate, as is its exact time range.

Discovery
Andrewsarchus is named for the famous explorer and fossil hunter Roy Chapman Andrews. It was discovered in June 1923 by Kan Chuen Pao, a member of Andrews' expedition, at a site in the Gobi Desert in Mongolia known as Irdin Manha [variants: Erdeni-Mandal and Erdenemandal ('jeweled mandala')] on the third Asiatic expedition that was led by Andrews and sponsored by the American Museum of Natural History. The skull is now on display at the American Museum of Natural History in New York; the lower jaw was not found.

Classification
It was classified in the clade Mesonychia due to the similarity in structure between its teeth and skull with those of other mesonychid species known from complete skeleton, however, much of this was based only on Osborn's original publication, and more recent studies have found it to have no special mesonychid affinities, instead grouping with various artiodactyl clades. Indeed one study (Spaulding et al.) has not only found them to be closer to entelodonts, but as kin to Whippomorpha in their Cetancodontamorpha.