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内蒙古大庙晚中新世仓鼠科一新种

2011年第49卷 第2期: 201-209

发表日期:2011-05-30来源:放大 缩小

 

编辑:张兆群,王李花,刘艳,刘丽萍

摘要:晚中新世是古老仓鼠类型向现代属种演化的重要转折时期。描述了产自内蒙古四子王旗大庙村附近DM02地点新发现的仓鼠科化石一新种,吴氏微仓鼠Nannocricetus wuae。该种臼齿低冠,齿尖呈尖锥形;m1的下前边尖呈单尖,具有向唇、舌两侧延伸的脊,无下中脊或极微弱;m2下前小脊很退化,下中脊有或无;M1前边尖窄,轻度二分;M3长大于宽。不同于被归入CricetodontinaeMegacricetodonDemocricetodon, 新种显示出牙齿结构的简化,上臼齿无前尖刺、前中脊和内外侧的附尖,下臼齿无下前小脊刺和内外侧的附尖,上臼齿3个齿根,下臼齿2个齿根。新种在牙齿形态上与陕西蓝田灞河组发现的原始微仓鼠Nannocricetus primitivus和内蒙古二登图的蒙古微仓鼠N. mongolicus最为接近,前者的m1下前边尖完全单尖,下前边尖与后面齿尖的连接完全缺失或极微弱,上下臼齿的中脊(下中脊)在部分标本上存在。这3个种皆为中国北部的地方类群,显示出明显的演化趋势:m1下前边尖的二分,M2/m2中脊(下中脊)的退化和前小脊(下前小脊)的发育。根据形态特征推测吴氏微仓鼠可能起源于众古仓鼠(Democricetodon), 并在中国渐进演化出原始微仓鼠和蒙古微仓鼠。依据吴氏微仓鼠的进化水平,参照已有的化石记录,并结合共生哺乳动物化石,推测该地点的时代可能为晚中新世最早期。

关键词:内蒙古大庙,晚中新世,仓鼠亚科

卷期:49卷 02期

 

A new species of Late Miocene hamster (Cricetidae, Rodentia) from Damiao, Nei Mongol

 

ZHANG Zhao-QunWANG Li-Hua, LIU Yan, LIU Li-Ping


Abstract
 The Late Miocene witnessed the transition of cricetids from ancient to modernized taxa. Here we describe a new cricetid species, Nannocricetus wuae, from DM02, near the Damiao Village, Siziwangqi, Nei Mongol. The new species is characterized by having low crowned molars with conical shaped cusps, single anteroconid on m1 with developed labial and/or lingual flanges, very weak to absent mesolophids on m1, variable mesolophid and very reduced anterolophulid on m2, narrow and slightly bifid anterocone on M1, and relatively long M3. Differing from the pattern of Cricetodontinae, Nannocricetus wuae shows great simplification of tooth structure. There is no paracone spur, anteromesoloph, or styles on upper molars, no spur of anterolophulid or stylids on lower molars. Root numbers are conservative, three for upper molars and two for lower molars. Morphologically, the new species shows close similarity to Nannocricetus primitivus and N. mongolicus. These three species constitute an endemic group confined to North China, and show progressive evolution in the splitting of the anteroconid on m1, reduction of the mesoloph(id), and development of anterolophule(id) on m2/M2 etc. Based on the evolutionary stage of the new species and associated fossils, we tentatively suggest an earliest Late Miocene age pending further confirmation by systematic study of other taxa and the paleomagnetic data.
Key words  Damiao, Nei Mongol; Late Miocene; Cricetinae

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