PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 109(2):397-405. 1996. Late Eocene entelodonts (Mammalia: Artiodactyla) from Inner Mongolia, China Spencer G. Lucas and Robert J. Emry (SGL) New Mexico Museum of Natural History and Science, 1801 Mountain Road N.W., Albuquerque, New Mexico 87104, U.S.A.; (RJE) Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, U.S.A. Abstract. — Previously undescribed specimens of Entelodon from the late Eo-cene (Ergilian) of Nei Monggol, China represent two species, small and large. We identify the small species as Entelodon gobiensis (Trofimov, 1952), because this is the oldest valid name available for a relatively small species of Asian Entelodon. E. diconodon (Trofimov, 1952) is a nomen dubium, and it is prob-able that E. ordosius (Young & Chow, 1956), E. major Biryukov, 1961 and E. orientalis Dashzeveg, 1965 are junior subjective synonyms of E. gobiensis (Trofimov, 1952). The large species is Entelodon dirus Matthew & Granger, 1923, a species previously known only from its holotype M3, but to which we now refer a lower jaw with p2-m3. In Asia, Entelodon is more common in strata of Ergilian (late Eocene) age; its Shandgolian (early Oligocene) occur-rences are few. Entelodonts originated in Asia during the middle Eocene, im-migrated to North America (late Eocene) and Europe (early Oligocene) and persisted until late Oligocene in Eurasia and North America. The last entelo-donts, from the early Miocene of North America, apparently arose from a separate, latest Oligocene emigration from Asia. Entelodonts were a family of Eocene-Ergilian, Shandgolian) as it was established Miocene giant suiform artiodactlys, some by Russell & Zhai (1987). with skulls nearly one meter long. They are Abbreviations used. — When used in den-especially well represented in the fossil rec-tal notations upper case letters denote upper ord in western North America (Peterson (skull) teeth and lower case letters denote 1909) and western Europe (Brunet 1979). lower (dentary) teeth. Institutional abbre-In Asia, the oldest entelodonts {Eoentelo-viations used are: AMNH — American Mu-don) are of middle Eocene (Irdinmanhan) seum of Natural History, New York; age, and the group persisted until the late IVPP — Institute of Vertebrate Paleontology Oligocene. The genus Entelodon is known and Paleoanthropology, Beijing; KAN — from the late Eocene (Ergilian) to early Oli-Kazakh Academy of Sciences, Almaty; gocene (Shandgolian), and two genera, MAN — Mongolian Academy of Sciences, Paraentelodon and Neoentelodon, are of Ulan Bator; PIN — Paleontological Institute late Oligocene (Tabenbulukian) age. In this of the Russian Academy of Sciences, Mos-article, we describe a sample of Entelodon cow. from the late Eocene of Nei Monggol (Inner Mongolia), China (Fig. 1), and clarify the Systematic Paleontology taxonomy of the Asian species of Entelo-don in Asia. We use the Asian "land mam-Family Entelodontidae Lydekker, 1883 mal age" terminology (e.g., Irdinmanhan, Genus Entelodon Aymard, 1847
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