Abstract:  New cricetids (Pappocricetodon neimongolensis sp. nov., Pappocricetodon cf. P.zhongtiaensis, Pappocricetodon sp.) are reported from the basal strata of the Irdin Manha Formation in the Huheboerhe section in Nei Mongol, China. P. neimongolensis is characterized by the following features: presence of a P4 or DP4; anterocone small; anterior arm of protocone on M1 well-developed and connected to anterocone; distinct paraloph joining protoconule and paracone; protocone on M1 lacking posterior arm; posterior arm of protocone present on M2; hypocone of M3 prominent; protoconid generally positioned anterior to metaconid on m1; posterior arm of protoconid on m2 complete; m3 unreduced, with “S”-shaped ectolophid. P. neimongolensis is morphologically similar to the early cricetid Pappocricetodon antiquus. Pappocricetodon sp. has a prominent anterior lobe, andPappocricetodon cf. P. zhongtiaensis has a distinct mesoloph. These fossils suggest that cricetids were already diversified in the Middle Eocene, and probably originated earlier than the Irdinmanhan.

摘要： 描述了产自内蒙古二连盆地呼和勃尔和剖面伊尔丁曼哈组底部砂岩中的3种仓鼠类化石：内蒙古祖仓鼠(新种) Pappocricetodon neimongolensis sp. nov., 中条祖仓鼠(相似种)Pappocricetodon cf. P. zhongtiaensis和祖仓鼠(未定种)Pappocricetodon sp.。P. neimongolensis的特征是有P4或者DP4; M1前附尖细小，前叶小，原尖前棱通常至原小尖横向延伸，再转向前颊侧与前附尖相连，无原尖后棱，原小尖与前尖通过前脊相连；M2原尖后棱较为发育；M3次尖不退化；m1下后尖比下原尖位置靠前；m2下原尖后棱完整，连接下后尖或直达下后尖基部；m3不退化，下外脊S型。新种形态与早期仓鼠类Pappocricetodon antiquus接近，但又略显原始。同时，在该层位还出现有M1前叶已经增大的Pappocricetodon sp.和中脊发育的Pappocricetodon cf. P. zhongtiaensis, 表明当时仓鼠类已出现多样化，其起源可能要早于中始新世的伊尔丁曼哈期。