摘要
Bohlin描述的柴达木动物群中的三趾马材料非常少 ,仅能证明三趾马在这个地点的存在。近年来新的野外考察在这一地区发现了更多的三趾马化石材料 ,至少包括 3个种 ,即Hipparioncf.H .chiai、H .weihoense和H .teilhardi。H .cf.H .chiai和H .weihoense在柴达木盆地的发现进一步证实了晚中新世早期 (保德早期 )动物群在这个地区的存在。柴达木盆地的H .teilhardi基本上与H .cf.H .chiai和H .weihoense产自同一层位 ,其时代也应为保德早期。H .cf.H .chiai和H .weihoense在柴达木盆地的发现为该地区在晚中新世早期为草原型环境的判断提供了更多的证据。H .
Fossil mammals collected from the northeastern Qaidam Basin by Swedish vertebrate paleontologist Birger Bohlin represent the first scientifically documented Hipparion (three-toed horse) fauna in the Tibetan Plateau. Fossil mammals from Qaidam represent a modest diversity of 22 taxa, but Hipparion materials are rather fragmentary, consisting of three dental fragments along with a few isolated postcranial elements. Despite such meager materials, the upper tooth fragments preserve typical Hipparion structures, such as an isolated protocone, and the presence of this important Late Miocene horse has not been in doubt since Bohlin’s (1937) description of the “Qaidam Fauna.” Mixed with the Hipparion horses, however, are also Middle Miocene taxa, such as basal deer Lagomeryx and Stephanocemas. Problems therefore arise in attempting to assign an age for the fauna. Bohlin’s (1937) original descriptions of the Qaidam mammals did not place them in a stratigraphic context, until more than 20 years later when he (Bohlin, 1960) published a brief description of the Qaidam geology. Unfortunately, most recent authors were unaware of this latter geologic summary, and as a result, all taxa were tacitly assumed to belong to a single fauna in treating the chronology of the Qaidam mammals (Qiu and Qiu, 1990, 1995; Qiu et al., 1999). By such an assumption, it is logical to regard the “Qaidam Fauna” as belonging to the earliest Late Miocene because of its possession of typical Late Miocene three-toed horse along with primitive deer that must have been Middle Miocene “leftovers.” In recent years, we have begun to systematically revisit the Qaidam mammal localities and to place newly collected materials in a modern stratigraphic context. It quickly becomes obvious that a substantial part of Bohlin’s “Qaidam Fauna” must have been collected from a long section of 2 000 m (total thickness >5 000 m at some local sections) that surely spans a considerable duration of time (Wang et al., 2000; Wang and Wang, 2001). More significantly, we have collected much better Hipparion materials in several localities. We are thus in a position to tease out certain components of the “Qaidam Fauna” on the basis of the morphological attributes of the Hipparion. Our findings confirm the existence of an early Late Miocene fauna in Qaidam, which was mixed with Middle Miocene faunas in previous studies without stratigraphic reference. Newly discovered Hipparion tends to bear primitive morphologies of the genus, signaling its close affinities to the North American ancestors. Such primitive morphologies are often associated with early Late Miocene strata equivalent to the European Vallesian age. Middle Miocene elements, such as Lagomeryx and Stephanocemas, are not associated with Hipparion.
出处
《古脊椎动物学报》
CSCD
北大核心
2004年第4期316-333,共18页
Vertebrata Palasiatica
基金
国家自然科学基金 (编号 :40 1 2 80 0 4
40 2 3 2 0 2 3 )
美国国家地理学会 (编号 :NGS 6771 -0 0
60 0 4-97)资助
