Sarkastodon

Early history In 1928, the American Museum of Natural History's Central Asiatic Expedition to Mongolia (one of a series which took place between 1921 and 1930) returned to the strata of the Irdin Manha Formation, from which large mammalian predators such as Andrewsarchus had been previously recovered. At the Chimney Butte site, part of the Ulan Shireh beds, an unknown participant in the expeditions discovered a partial right lower jaw. This jaw was later catalogued as AMNH 26302. Two years later, in the final Central Asiatic Expedition, while prospecting around southwest of Iren Dabasu, Inner Mongolia, discovered the partial skull and lower jaws of a large predatory animal. It was recognised as belonging to a new taxon, specifically a "relatively colossal" oxyaenid (then part of the order "Creodonta"). In 1938, this second specimen, AMNH 26641, was described by Walter W. Granger, who made it the holotype of a new genus and species, Sarkastodon mongoliensis''. The jaw discovered in 1928 was designated as the paratype. The generic name comes from the Ancient Greek σαρκάζω ("to tear flesh"), and οδούς ("tooth"). Classification Sarkastodon is a member of the family Oxyaenidae, and the link between the two is predicated largely on the presence of a blade on the metastyle of the first molar, a trait present in many eutherians. In a 1938 revision of the family, R. H. Denison placed Sarkastodon within the subfamily Oxyaeninae, alongside other large taxa such as Patriofelis. == Description ==

of S. mongoliensis Sarkastodon was the largest of the oxyaenids, measuring approximately in length. In 2009, Boris Sorkin provided an estimate for the body mass of S. mongoliensis based on the size of the lower jaw and extrapolations from modern felids. The maximum mass estimate he recovered was , roughly twice that of the American lion in the same analysis. He did, however, note the caveat that S. mongoliensis shows significant morphological differences from its extant model (the African lion), so this estimate may not be as reliable as some of the others in the same analysis. Skull and dentition The skull of Sarkastodon's holotype is incomplete, though what is preserved, when measured from the anterior (front) tip of the premaxilla to the posterior (rear) border of the glenoid fossa, is in length; measured at the zygomatic arches, it is in width. Overall, the skull was around fifty percent larger than that of Patriofelis. It was similarly short, broad, and massively built. The mandible was deep, with a heavy symphysis. Granger's diagnosis of S. mongoliensis was based primarily on dental characteristics. The lower incisors were very small, displaced into a more posterior position by the massive, robust, and unusually anteriorly-placed canines. Both the upper and lower sets of premolars were large, The second upper one was offset into a position diagonal to the rest of the tooth row. The first upper molar formed a large shearing tooth with a small protocone. == Palaeoenvironment ==

The first Sarkastodon specimen to be recovered came from the Irdin Manha Formation in Inner Mongolia, specifically the Chimney Butte site, or simply by "eight miles north of Tukhum Lamasery". Also known from the Chimney Butte locality are the turtles cf. Adocus, Anosteira, Testudo, and an indeterminate trionychid, the birds Eogrus, Telecrex, and an indeterminate buteonine (hawk), the pantodont Pantolambdodon, and Saykanomys, the lagomorph Shamolagus, the didymoconid Kennatherium, and the paraceratheriid rhinocerotoid Forstercooperia. == References ==