内蒙古西部额济纳旗及邻区中二叠统腕足类动物群的特征和时代

额济纳旗及其邻区中二叠统产丰富的腕足动物群，该动物群具有北方冷水动物和特提斯暖水动物混生的特点，划分为Spiriferella-Kochiproductus-Yakovlevia 组合，称为“哲斯动物群”。在生物古地理分区上，该区为北方生物大区和特提斯生物大区之间的过渡带，称为中蒙生物省。动物群的组成、丰度和分异度等特征在银-额（银根-额济纳旗）盆地的东西部有明显的差异：盆地西部北山地区海水较浅，腕足动物群丰度高，分异度略低，以个体较大、壳体较厚的冷水分子占优势，共生少量的双壳类和珊瑚；东部杭乌拉地区海水略深，腕足动物群丰度稍低，分异度较高，含有大量的小个体腕足，共生冷水型珊瑚和丰富的海百合类，世界广布分子和暖水分子超过一半。说明该腕足动物群在受纬度和温度控制的同时，也受水体深度的影响，在同一海盆的不同环境中表现出不同的特点。通过对该动物群的起源、区域分布特点和共生生物的分析，认为额济纳旗及其邻区的哲斯动物群的时限为罗甸期—孤峰期。

Characteristics and geological age of Middle Permian brachiopod fauna from Ejin Banner and its vicinities, western Inner Mongolia

Abundant brachiopods have been recorded from the Middle Permian strata of Ejin Banner and its vicinities. This fauna, called Zhesi Fauna, is characterized by a mixed fauna composed of boreal cool-water elements and Tethyan warm-water elements. The brachiopod Spiriferella-Kochiproductus-Yakovlevia assemblage has been recognized from this fauna. In paleobiogeography, Ejin Banner and its vicinities were located in a transitional position between Boreal and Tethyan provinces, called Sino-Mongolia province. The fauna pattern in eastern Yine basin is different from that in western Yine basin. In the shallow-water Beishan of western Yine Basin, the brachiopod is dominated by large-sized and thick-shelled cool-water elements, with a higher abundance and a slightly lower diversity in association with a few bivalves and corals, while in the relatively deep-water Hangwula of eastern Yine basin, the brachiopod is dominated by relatively small-sized cosmopolitan warm-water elements, with a slightly lower abundance and a higher diversity in association with cool-water corals and abundant encrinites. This pattern indicates that the distribution of brachiopods is controlled not only by latitude and temperature but also by water depth. The geological age of Zhesi Fauna is assigned to the Roadian to Kufengian, based on an analysis of its origin, spatial distribution and associated fauna.