第50卷第3期古脊椎动物学报pp.237-2442012年7月VERTEBRATAPALASIATICA脸.12内蒙古二连盆地呼和勃尔和剖面中始新世仓鼠类化石'）李茜（中国科学院古脊椎动物与古人类研究所，脊椎动物进化系统学重点实验室北京100044）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）Pappocricetodonneinumgolensissp.nov.,中条祖仓鼠（相似种）P叩/*>"奴如0"cf.P.zhongtiaensis和祖仓鼠（未定种）Pfl明sp.oP.neimongolensis的特征是有P4或者DP4；Ml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;ml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F后尖基部;m3不退化，下外脊S型°新种形态与早期仓鼠类Pappocricetodonantiquum接近，但又略显原始。同时，在该层位还出现有Ml前叶已经增大的Pappocricetodonsp.和中脊发育的Pappocricetodoncf.P.zhongtiaensut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。关键词：内蒙古呼和勃尔和，中始新世，伊尔丁曼哈组,仓鼠类中图法分类号：Q915.873文献标识码:A文童编号：1000-3118（2012）03-0237-08MIDDLEEOCENECRICETTOS(RODENTIA,MAMMALIA)FROMTHEERLIANBASIN,NEIMONGOL,CHINA(KeylaboratoryofEvolutionarySystematicsofVertebrates,InstituteofVertebratePaleontologyandPaleoanthropology,ChineseAcademyofSciencesBeijing100044】iqian@ivpp.ac.cn)AbstractNewcricetids(Pappocricetodonneinwngolensissp.nov.,Pappocricetodoncf.P.zhong-tiaensis,Pappocricetodonsp.)arereportedfromthebasalstrataoftheIrdinManhaFormationintheHuheboerhesectioninNeiMongol,China.P.neimongolensisischaracterizedbythefollowingfeatures:presenceofaNori)P4；anteroconesmall；anteriorarmofprotoconeonM1well-developedandconnectedtoanterocone;distinctparalophjoiningprotoconuleandparacone；protoconeonMllackingposteriorarm；posteriorarmofprotoconepresentonM2；hypoconeofM3prominent；protoconidgene-rallypositionedanteriortometaconidonml;posteriorarmofprotoconidonm2complete；m3duced,with"S"-shapedectolophid.P.neinwngolensisismorphologicallysimilartotheearlycricetidPappocricetodonanliquus.Pappocricetodonsp.hasaprominentanteriorlobe,andPappocricetodoncf.P.zhongtiaensishasadistinctmesoloph.ThesefossilssuggestthatcricetidswerealreadydiversifiedintheMiddleEocene,andprobablyoriginatedearlierthantheIrdinmanhan.KeywordsHuheboerhe,NeiMongol；MiddleEocene；IrdinManhaFormation；Cricctidae1）中国科学院知识创新工程重要方向项目（编号：KZCX2-EW-106）、国家自然科学基金（批准^=40532010,40802009）.国家重点基础研究发展计划项目（编号：2012CB821900）和中国科学院化石发掘与修理专项资助。收稿日期：2011-11-29IntroductionMostknownEocenecricetidsarefromEastandCentralAsia,especiallyChinaandKazak-LIQianLIQianunre-werestan.ThegenusPappocricetodon(Tong,1992；WangandDawson,1994)isconsideredtobethemostprimitivecricetid.PalasiomysandRaricricetodon(Tong,1997)weredescribedmorerecently,andhaveprovidednewinsightintotheearliestcricetids.TheoriginofCricetidaeandtherelationshipsamongtheearliestspeciesfromCentralandEastAsiaarestilldisputed,butmostevidencesuggeststhatcricetidsoriginatedinAsiaratherthanNorthAmerica(Emry,2007).Rodriguesetal.(2010)suggestedthattheearliestoffshootofthecricetidcladeistheAsiangenusPalasiomys,andthatthegenusPappocricetodondisplaysacompletecricetidplanassociatedwithboththelossP4andthedevelopmentofananteroconeonMl.Twelvemammal-bearinghorizonshavebeenrecognizedinthePaleogeneoftheHuheboerhearea,andthesehorizonsarela...