Abstract: We describe a new bunodont anthracothere (Mammalia; Artiodactyla),Myaingtherium kenyapotamoides gen. et sp. nov., discovered from the upper middle Eocene Pondaung Formation of Myanmar. The specimens consist of upper and lower dentitions with fragmentary jaws. Myaingtherium is one of the basal anthracotheres and is comparable in size and overall morphology to a small-sized Pondaung anthracothere,Anthracokeryx tenuis. However, Myaingtherium is more similar in dental morphology to Anthracotherium and Anthracohyus rather than to Anthracokeryx in having more bunodont dentition. Myaingtherium is characterized particularly by having a very reduced molar paraconule among bunodont anthracotheres. Some dental characteristics of Myaingtherium, such as a reduced molar paraconule with bunodont dentition and a median accessory cusplet on the lower molars, are reminiscent of those of the Kenyapotaminae (most primitive fossil hippopotamuses) and hippo-like anthracotheriidKulutherium from the Miocene of Africa, implying a possibility that Myaingtheriummight be phyletically related to the Kenyapotaminae. Although more evidences are necessary to test the phyletic relationships of Myaingtherium, this discovery reinforces that the Pondaung anthracotheres are an important fauna for testing and understanding the phyletic relationships and early evolution of the hippo-anthracothere clade.

摘要： 描述了缅甸中始新统上部邦唐组发现的一种新的丘齿形石炭兽Myaingtherium kenyapotamoides gen. et sp. nov.。标本为破碎的上下颌骨。Myaingtherium是一种基干石炭兽类，其大小和基本形态可以与邦唐一种小的石炭兽Anthracokeryx tenuis相对比。然而，Myaingtherium因具有更丘型化的齿列而与Anthracotherium和Anthracohyus在牙齿形态上更相似。在丘型齿石炭兽类中，Myaingtherium以臼齿前小尖非常退化为特点。Myaingtherium的一些牙齿特征，如具有退化的臼齿前小尖的丘型齿列和下臼齿上具有一个中间附尖，与Kenyapotaminae (最原始的化石河马)以及非洲中新世类似河马的石炭兽Kulutherium的牙齿特征相似，暗示Myaingtherium在谱系上可能与Kenyapotaminae有关。尽管需要更多的证据来检验Myaingtherium的谱系关系，但这个发现强化了邦唐石炭兽类在检验和理解河马–石炭兽支系的谱系关系和早期演化方面的重要性。