甘肃东乡首次发现熊亚科化石——龙担哺乳动物群补充报道之二
감숙동향수차발현웅아과화석——룡담포유동물군보충보도지이
FIRST URSINE BEAR MATERIAL FROM DONGXIANG.GANSU——Addition to the Longdan Mammalian Fauna(2)
  • 万方数据
    古脊椎动物学报 고척추동물학보
    VERTEBRATA PALASIATICA
    2009年 4期 245-264 ,共20页

    邱占祥%邓涛%王伴月

    구점상%산도%왕반월

    甘肃东乡%上新世%早第四纪%龙担哺乳动物群%熊亚科%分类 甘肅東鄉%上新世%早第四紀%龍擔哺乳動物群%熊亞科%分類
    감숙동향%상신세%조제사기%룡담포유동물군%웅아과%분류
    Dongxiang of Gansu%Pliocene%Early Quaternary%Longdan mammlian fauna%Ursinae%classification
    2006年作者在和政县发现了两件产自东乡龙担动物群的熊类化石:一完整下颌(HMV1422)和一个咬合在一起的头骨及下颌(HMV 1454).熊类系龙担哺乳动物群中未曾描述过的新成员.这两件标本虽然有少许不同,但都和李亦征(1993)所记述的沂南熊Ursus(Protarctos) yinanensis 十分接近,而被归入该种.该种修订后的鉴别特征是:头骨长头型,头长接近中等大小的现生黑熊,头骨最大宽约为最大长的一半;矢状嵴长,约为顶长的1/3;眶下孔与眼眶前缘相距近,两者均在M1上方;颧骨前端仅组成眼眶下缘,其后端止于关节窝前缘水平;硬腭短,齿列之后的腭长小于P4长的1.5倍或M2长的3/4.前臼齿数目全;P4原尖小,位于裂凹正内方;M1短长方形,宽/长～80%;M2跟座中长,M2宽/长56%～58%;M2长/M1长133%～153%.m1无前下后尖及前下内尖,分隔下三角座和跟座的横沟窄(前后),横沟中没有明显的嵴和沟;m2短于m1,其前、后接近等宽.与U. Boeckhi相比,P4相对更小;臼齿相对更窄长;M1不呈五边形;M2跟座更大;m1横沟短,V形.现生熊亚科的6个种在分子和生化特性上非常接近,且其分异的时间非常短.这使以生化和分子生物学为研究手段的遗传学家越来越倾向于把它们归入同一个属,即Ursus.但是以形态特征为研究对象的古生物学家却大多依据形态上的明显差异而把它们分成多个属.不过古生物学家也常把欧亚大陆上新世-第四纪早期的熊类化石简单地归入 Ursus 一个属.在对比研究东乡熊化石时,我们对欧亚大陆同期的熊化石作了较仔细的观察,发现m1的形态变化在熊亚科的演化中分异显著,在分类中应具重要意义.结合头骨及牙齿的其他特征,这一时期熊类化石主要可以分为三组:1)m1形态简单者,无前下后尖和前下内尖,横沟表面基本光滑.2)m1具嵴形图案者,具前下后尖,但无前下内尖,在三角座后壁和横沟中形成V,Y或X形嵴.这一组熊类的m1和现生黑熊者最为接近.3)m1具前下后尖、前下内尖,次级附尖很发育,主尖及附尖多为圆锥形.这一组熊类的m1和现生棕熊者最为接近.属于第一组的有Bar(o)th-K(o)pecz的U.boeckhi,沂南熊及Serrat d'en Vacquer 的一件左下颌(1890年描述).第二组包括产自Perrier,weze,Layrna,W(o)lfersheim等地点的熊类及Serrat d'en Vacquer 的一件头骨及下颌(1892年描述).第三组包括发现十欧洲众多地点(Val d'Arno,st.Vailier等)的U. Etruscus.上述j组熊类在m1形态上的差异和组内变异的程度,使我们倾向于把它们分为不同的属,其属名分别应为:Protarctos,Euarctos和Ursus.Protarctos包括P.boeckhi(MN 14),P.ruscinensis(MN 15)和P.yinanensis(相当于MN 16-17).Euarctos包括E.pyrenaicus (MN 15),E. Minimus (MN 16-17)和现牛美洲及亚洲的黑熊.而Ursus则包括U. Etruscus(MN 17)及许多后期类犁,如U.spelaeus等,以及现生的U. Arctos(可能还有u.marilimus).
    2006년작자재화정현발현료량건산자동향룡담동물군적웅류화석:일완정하합(HMV1422)화일개교합재일기적두골급하합(HMV 1454).웅류계룡담포유동물군중미증묘술과적신성원.저량건표본수연유소허불동,단도화리역정(1993)소기술적기남웅Ursus(Protarctos) yinanensis 십분접근,이피귀입해충.해충수정후적감별특정시:두골장두형,두장접근중등대소적현생흑웅,두골최대관약위최대장적일반;시상척장,약위정장적1/3;광하공여안광전연상거근,량자균재M1상방;권골전단부조성안광하연,기후단지우관절와전연수평;경악단,치렬지후적악장소우P4장적1.5배혹M2장적3/4.전구치수목전;P4원첨소,위우렬요정내방;M1단장방형,관/장～80%;M2근좌중장,M2관/장56%～58%;M2장/M1장133%～153%.m1무전하후첨급전하내첨,분격하삼각좌화근좌적횡구착(전후),횡구중몰유명현적척화구;m2단우m1,기전、후접근등관.여U. Boeckhi상비,P4상대경소;구치상대경착장;M1불정오변형;M2근좌경대;m1횡구단,V형.현생웅아과적6개충재분자화생화특성상비상접근,차기분이적시간비상단.저사이생화화분자생물학위연구수단적유전학가월래월경향우파타문귀입동일개속,즉Ursus.단시이형태특정위연구대상적고생물학가각대다의거형태상적명현차이이파타문분성다개속.불과고생물학가야상파구아대륙상신세-제사기조기적웅류화석간단지귀입 Ursus 일개속.재대비연구동향웅화석시,아문대구아대륙동기적웅화석작료교자세적관찰,발현m1적형태변화재웅아과적연화중분이현저,재분류중응구중요의의.결합두골급아치적기타특정,저일시기웅류화석주요가이분위삼조:1)m1형태간단자,무전하후첨화전하내첨,횡구표면기본광활.2)m1구척형도안자,구전하후첨,단무전하내첨,재삼각좌후벽화횡구중형성V,Y혹X형척.저일조웅류적m1화현생흑웅자최위접근.3)m1구전하후첨、전하내첨,차급부첨흔발육,주첨급부첨다위원추형.저일조웅류적m1화현생종웅자최위접근.속우제일조적유Bar(o)th-K(o)pecz적U.boeckhi,기남웅급Serrat d'en Vacquer 적일건좌하합(1890년묘술).제이조포괄산자Perrier,weze,Layrna,W(o)lfersheim등지점적웅류급Serrat d'en Vacquer 적일건두골급하합(1892년묘술).제삼조포괄발현십구주음다지점(Val d'Arno,st.Vailier등)적U. Etruscus.상술j조웅류재m1형태상적차이화조내변이적정도,사아문경향우파타문분위불동적속,기속명분별응위:Protarctos,Euarctos화Ursus.Protarctos포괄P.boeckhi(MN 14),P.ruscinensis(MN 15)화P.yinanensis(상당우MN 16-17).Euarctos포괄E.pyrenaicus (MN 15),E. Minimus (MN 16-17)화현우미주급아주적흑웅.이Ursus칙포괄U. Etruscus(MN 17)급허다후기류리,여U.spelaeus등,이급현생적U. Arctos(가능환유u.marilimus).
    Two bear specimens obtained from Dongxiang area were noticed from the purchased "dragon bones" of the Hezheng County in 2006: a complete mandible (HMV 1422) and a skull in association with its mandible ( HMV 1454). They represent the first bear material of the Longdan mammalian fauna. Although slightly different in morphology, they are found to be very close to Ursus (Protarctos) yi-nanensis described by Li Yizheng in 1993 , and thus referred to this species. A revised diagnosis of this species is given in the text. Based on high degree of genetic homogeneity and short divergence time of the 6 extant ursine species, molecular and biochemical biologists are being increasingly confident that all the extant ursines should be assigned to a single genus, Ursus. On the other hand, most of the paleontologists, governed by their factual knowledge of morphologic distinctions between these ursine species, are inclined to separate them into different genera. Nevertheless, the Eurasian Pliocene - Early Quaternary bear fossils have often been indiscriminately referred to Ursus. A closer observation of the bear materials during our comparative study of the Dongxiang bear specimens revealed great variety in bear ml morphology, implying its particular importance in classification of the Ursinae. Based mainly on ml morphology, coupled with other skull and dental features, the majority of the Eurasian Pliocene-Early Quaternary bears can possibly be divided into three groups: 1) The bears having simple ml's, lacking pre-metaconids and pre-entoconids, with the transverse groove surfaces being basically smooth. 2) Those having ml's with pre-metaconids and V-, Y-, or X-shaped ridges on the transverse grooves, but no pre-entoconids. The ml morphology of this group is close to that of the extant black bears. 3) Those having ml' s with bun-odont pre-metaconids, pre-entoconids and well developed accessory cusplets. The ml morphology of this group is basically that of the extant brown bears. The 1~(st) group includes the specimens from Barfith-Kopecz, Yinan (and Dongxiang), and the left hemimandible of Serrat d'en Vacquer described in 1890. The 2~(nd) group includes those from Perrier, Weze, Layna, Wolfershein, etc., and the skull and mandible from Serrat d' en Vacquer described in 1892. The 3~(rd) group includes U. etruscus of many European localities, among which Val d' Arno and St. Vallier are the principal ones. Morphologic distinctions between, and the degree of variability within, these three groups strongly inclined us to separate them into different genera. If the above viewpoint is tenable, three generic names would be suitable for them; Protarctos, Euarctos and Ursus. In this case, Protarrtos would include P. boeckhi ( MN 14) , P. ruscinensis ( MN 15) and P. yinanensis (equivalent to MN 16-17). Euarctos would include E. pyrenaicus ( MN 15) , E. minimus ( MN 16-17) and the extant American and Asian black bears, llrsus would contain U. etruscus (MN 17) , U. spelaeus etc., and the extant brown bear (and possibly U. maritimus).
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