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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。
In this paper, we describe the Miocene heart-shaped fossil shell eggs from the Garshin Adeg (17.5Ma) and Baghdadhula (7.11 ± 0.48Ma) sites in Inner Mongolia. Among them, the thickness of eggshell material of Gaoshin Aidege spot is about 2.12mm, and its outer surface is smooth with pinholes. Diameter section shows the surface of the crystal layer is very thin, vertebral layer and columnar layer ratio of about 1: 2.4. The material characteristics of the Baghdad Wula site are similar to those of Gaoshin Aideg, except that the former has a slightly thinner thickness (average 2.02mm) and a lower stomatal density. These characteristics are similar to those of the aepyornithid eggshell, so that the aepyornithid eggshell can be extended to East Asia; and the aepyornithid eggshell at the Garshin Adeger site serves as an early representative of this type. By comparing several locations in Eurasia, we found that the aepyornithid eggshell occurred significantly earlier than the struthionid eggshell in Eurasia, which seems to indicate that the former is another kind of animal different from that of “ostrich”. At the same time, the assemblage of two fauna reflects the aridification process of the Miocene Mongolia Plateau, and the change of stomatal density may be directly related to this process.