摘要
本文描述了内蒙古嘎顺音阿德格(17.5Ma)和宝格达乌拉(7.11±0.48Ma)地点的中新世平胸鸟类蛋壳化石。其中嘎顺音阿德格地点的蛋壳材料厚度约为2.12mm,其外表面光滑具针孔型气孔。径切面显示其表面晶体层甚薄,椎体层与柱状层之比约为1:2.4。宝格达乌拉地点的材料特征与嘎顺音阿德格的材料接近,所不同的是前者厚度略薄(平均2.02mm),且气孔密度较小。这些特征与aepyornithid型蛋壳特征接近,因此aepyornithid型蛋壳分布可以扩展至东亚;而嘎顺音阿德格地点的aepyornithid型蛋壳可以作为这一类型的早期代表。通过欧亚大陆几个地点间的对比,我们发现aepyornithid型蛋壳在欧亚大陆出现的时间显著早于struthionid型蛋壳,这似乎说明前者是区别于"鸵鸟"的另一类动物。与此同时,两个动物群的组合面貌反映出中新世蒙古高原的干旱化过程,蛋壳气孔密度的变化可能与这一过程有直接关系。
Some Miocene ratite eggshell fragments from Gashunyinadege (about 17.5 Ma) and Baogedawula (7.11 ± 0.48 Ma), Inner Mongolia, China, are described. The outer surfaces of eggshell fragments from Gashunyinadege are smooth with a sting pore pattern, while their entire thickness is around 2.12 mm. In a cross-sectional view, the surface crystal layer is very thin and the ratio of cone layer to the those from Gashunyinadege, but seem much thinner and have a lower pore density. Both characteristics fit aepyornithid-type eggshells, implying that the distribution of aepyornithid-type eggshells can be extended to East Asia. The sediments at Gashunyinadege date to approximately 17.5 Ma, implying that the specimens from this locality are relatively early examples of aepyornithid-type eggshells. Aepyornithidtype eggshells seem to have appeared in Eurasia much earlier than struthionid-type eggshells. The faunal compositions in the two localities reflect gradual drying of the Mongolian plateau during the Miocene. A reduction in the number of pores 10 Ma ago, probably occurred in response to this drying process.
基金
supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(KZCX2-YW-120)
the Key Laboratory of Evolutionary Systematics of Vertebrates,Chinese Academy of Sciences(2010LESV007)
