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陕西蓝田是我国晚中新世地层发育最完整的地区之一。新近纪哺乳动物分期中的灞河期即根据该地区灞河组发现的化石而命名。1997至2001年度的中芬合作在灞河组发现大量的新层位与化石标本。连续的地层剖面与大量的化石资料为进一步认识晚中新世哺乳动物的演化历史提供了很好的基础。灞河组发现的仓鼠可以归入两个属:微仓鼠Nannocricetus和科氏仓鼠Kowalskia。微仓鼠的分布时限较长,从灞河组的底部到中上部层位,古地磁研究指示其年代为10.2～8 Ma。根据形态特征与测量数据,发现的微仓鼠标本被归入同一种Nannocricetus primitivus。其主要特征有:个体很小;m1的下前边尖在中度或重度磨蚀的标本上呈单尖,metalophulidⅠ存在,但metalophulidⅡ缺如;M1前边尖与原尖单连接;M3很退化。与Nannocricetus mongolicus相比,m1的下前边尖更少分开,且在唇侧有向后延伸的弱脊,下前小脊很弱或缺失,m2的舌侧前边尖较发育,M1前边尖与原尖单连接,M3次尖较发育且缺失后尖。推测Nannocricetus primitivus是N.mongolicus的直接祖先类型,向后者转换的时间大约发生在7～8 Ma。根据新的化石材料重新修订了微仓鼠的属征:个体很小的仓鼠;上臼齿的中脊与下臼齿的下中脊完全缺失或极不发育;m1下前边尖呈单尖或较少分开;m2的下次尖靠舌侧,使得m2的后部较窄,m2中原谷向前延伸不太远;M3很退化。科氏仓鼠的标本很少,仅发现在剖面的上部,其时代稍早于8 Ma,与云南禄丰的年代大致相当,是目前中国发现的最早纪录之一。推测科氏仓鼠在8 Ma前从欧洲迁移至中国。
Lantian, Shaanxi Province is one of the most complete regions of Late Miocene strata in China. The Neogene Mammalian staging is based on the fossils found in the Tahe Formation in the area. Sino-Finnish cooperation between 1997 and 2001 revealed a large number of new stratigraphic and fossil specimens in the Tahe Formation. Continuous stratigraphic profiles and a large number of fossil data provide a good foundation for further understanding of the evolutionary history of late Miocene mammals. Hamsters found in Tuanhe group can be classified into two genera: Nannocricetus and Kowalskia. The distribution of the hamster is relatively long, from the bottom to the middle-upper strata of the Tahe Formation. Palaeomagnetic studies indicate that the age of the hamsters is 10.2-8 Ma. According to morphological characteristics and measurement data, the micro-hamsters were found to belong to the same Nannocricetus primitivus. The main features are: the individual is very small; m1 under the tip of the tip in the moderate or severe abrasion specimens were single-pointed, metalophulid Ⅰ exist, but lack of metalophulid Ⅱ; Compared with Nannocricetus mongolicus, the lower anterior apices of m1 are less divided, and there are weak ridges extending backward on the labial side. The anterior inferior cerebellar is weak or absent. The anterior apices of m2 are more developed than those of Nannocricetus mongolicus. A single connection, M3 times more developed and the lack of apex. It is speculated that Nannocricetus primitivus is a direct ancestral type of N. mongolicus, and the transition to the latter occurs in about 7-8 Ma. According to the new fossil material, the attributes of the micro hamsters were revised: individual hamsters; the lower and upper midrib of the upper molars and the lower molars are completely or very undeveloped; ; m2 next sharp side of the tongue, making the back of the m2 is narrow, m2 in the valley extends forward not too far; M3 is very degraded. Koch hamster specimens are rare, only found in the upper part of the profile, the era earlier than 8 Ma, roughly the same age with the Yunnan Lufeng, is currently one of the earliest records found in China. Speculated that Kobus hamster 8M Ma from Europe to China.