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描述了20世纪80年代在江苏泗洪早中新世下草湾组采集的5属5种仓鼠类动物化石,其中包括1新属和4新种,即Eumyarioninae亚科的Alloeumyarion sihongensis gen.et sp.nov.,Cricetodontinae亚科的Cricetodon wanhei sp.nov.,Copemyinae亚科的Primus pusillus sp.nov.和Democricetodon suensis sp.nov.,以及Megacricetodontinae亚科的Megacricetodon sinensis Qiu et al.,1981。Cricetodon,Democricetodon和Megacricetodon属常见于早、中新世地层,并有较广泛的地理分布;Primus属仅发现于印度次大陆下中新统;新属Alloeumyarion可能与Eumyarion属有较接近的亲缘关系。泗洪发现的仓鼠是该哺乳动物群中种类最多、材料最丰富的一类啮齿动物。泗洪地点位于现代东洋界与古北界的过渡地带,这一化石组合的出现为我国中新世哺乳动物地理及其演变的研究提供了有用的证据。根据仓鼠类化石的研究,下草湾组的时代很可能属于早中新世晚期,或者是中国陆相哺乳动物时代的山旺期,大体相当于欧洲陆相哺乳动物时代的奥尔良期或MN4带的时代。这些新属和新种的特征如下:异美鼠(新属)(Alloeumyarion gen.nov):美鼠亚科中个体中等者。牙齿低冠;齿尖中度鼓胀、趋于脊形。上臼齿三根,内谷前指向,原脊和后脊近横向平行排列,无前尖后刺;M1前叶前后向伸长,前边尖简单,有宽大的后边谷,但无前脊刺;M2的原脊稍前指向,舌侧与原尖前边连接;M3的后部明显退化。下臼齿双根,下外谷横向、近对称;m1下前边尖简单,下前脊单一,下原尖和下次尖的后臂不很发育;m2无下次尖后臂。万合古仓鼠(新种)(Cricetodon wanhei sp.nov.):个体中等大小。M1和M2四齿根,在早期磨蚀的牙齿中有清楚的后边谷,但外脊发育弱;M1的前边尖简单或略微分开;M2前边脊舌侧支模糊;M3冠面近圆形,多数牙齿的内谷为连接原尖和次尖的脊封闭,时见原脊后刺;m1具双下后脊和短的下中脊;m3与m2等长或比m2稍大,具短的下前边脊舌侧支。细先鼠(新种)(Primus pusillus sp.nov.):个体小。M1的前叶前后向较短,前边尖和前边脊弱,原脊略后指与原尖后臂连接,后脊稍前指与次尖前臂相连;m1具较宽且呈刀形的前边尖,下次脊前指向。苏众古仓鼠(新种)(Democricetodon suensis sp.nov.):个体中等大小,颊齿低冠,齿尖和齿脊较弱,臼齿中脊的长度一般在中长至长之间,上臼齿的双原脊不甚发育。M1的前边尖简单而窄,原尖前臂和原脊II间常有一脊相连;M2的后脊横向或稍前向;M2和M3多具“轴脊”(“axi-oloph”);m1的下前边尖单一而窄小;多数m1和m2有下外中脊;m3的下中脊通常显著。
Describes five genera of 5 species of hamster fossils collected from the Lower Paleo-Miocene Bay in Sihong, Jiangsu Province in the 1980s, including 1 new genera and 4 new species, the Alloeum yarion sihongensis gen. Et sp. Of the subfamily Eumyarioninae. nov., Cricetodon wanhei sp. nov. of Cricetodontinae subfamily, Primus pusillus sp. nov. and Democricetodon suensis sp. nov. of Copemyinae subfamily, and Megacricetodon sinensis Qiu et al., 1981 of Megacricetodontinae subfamily. Cricetodon, Democricetodon and Megacricetodon genera are common in Early and Miocene strata and have a wider geographical distribution. Primus is found only in the Indian subcontinent. The new genus Alloeumyarion may have a closer genetic relationship with Eumyarion. The hamsters found in Sihong are the most abundant and richest species of rodents in this group of mammals. The Sihong site is located in the transitional zone between the modern Toyohae and the ancient North Boundary. The emergence of this fossil assemblage provides useful evidence for the study of the mammalian geography and its evolution in China. Based on studies of hamster fossils, the Xiaochawan Formation is likely to belong to the late Early Miocene or the Shanwang period of the continental mammalian age of China, roughly equivalent to the Orleansian or MN4 belts of the continental mammalian age of Europe era. The characteristics of these new genera and new species are as follows: Alloeum genus of the United States (New genus). Tooth low crown; tip moderate swelling, tends to ridge. On the molar three, before the valley point, the original ridge and the posterior ridge near the horizontal parallel arrangement, no pricker after prickles; M1 before and after the anterior lengthening, the tip of the apical simple, with a large valley behind, but no anterior spinal spine; M2 The anterior ridge of the anterior pointing, lingual side connected with the anterior tip; M3 rear significantly degenerated. Lower molars double root, under the outer valley lateral, near symmetry; m1 under the front apex simple, the next anterior ridge a single, the next point and the next next sharp tip of the hindbrain is not very developed; Cricetodon wanhei sp.nov.: Individual medium size. M1 and M2 four-tooth root, in the early erosion of the teeth in the valley after the clear, but the weakness of the external ridge; M1 apex simple or slightly separated; M2 anterior spondylolisthesis; M3 crown near the circle, the majority The inner valley of the teeth is connected to the original tip and the next tip of the ridge closed, see the original spinal posterior puncture; m1 with double lower posterior ridge and short lower midline; m3 and m2 equal or slightly larger than m2, with short Frontal spondylolisthesis. Primus pusillus sp. Nov.: Individual small. M1 before and after the anterior to the shorter, the anterior tip and the anterior ridge is weak, the original ridge of the posterior means connected with the original tip, posterior apex refers to the forearm and the next tip; m1 with broad and blade-shaped anterior tip , The next ridge before point. Democricetodon suensis sp. Nov.: Individual medium size, low crest of cheek teeth, weak tips and ridges, length of midrib ridge in mid-long to long, upper molar The double ridge is not well developed. The apex of M1 is simple and narrow, the anterior forearms and ridges II are often connected to one ridge, the posterior ridge of M2 is transverse or slightly anterior, the M2 and M3 are more than “axi-oloph” ); the lower anterior tip of m1 is single and narrow; the majority of m1 and m2 have lower outer ridges; and the lower mid-ridge of m3 is usually significant.