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内蒙古乌海市以南约２５ｋｍ的桌子山地区中奥陶世（ｅａｒｌｙｌａｔｅＡｒｅｎｉｇ）三道坎组底部产一种原始的扭月贝类腕足动物，经笔者鉴定，为中华西方贝（新种）（Ｈｅｓｐｅｒｉｎｉａｓｉｎｅｎｓｉｓｓｐ．ｎｏｖ．），系统切片研究证实其为迄今所知最古老的一种扭月贝类，其双叶型主突起略突伸于铰合缘的后方、低而较弱的铰窝脊向侧后方延伸靠近铰合缘等特征都表明该种属于扭月贝科（Ｓｔｒｏｐｈｏｍｅｎｉｄａｅ）。实现从褶脊贝类向扭月贝类的演化需要在背壳内部建立这样一些形态上的演化新质：双叶型主突起，一对朝后侧方略弯曲的铰窝脊，横肌脊，以及侧隔板，所有这些构造特征，Ｈｅｓｐｅｒｉｎｉａｓｉｎｅｎｓｉｓｓｐ．ｎｏｖ．均已具备，因此，这表明了扭月贝类与褶脊贝类的分化要早于晚Ａｒｅｎｉｇ。除Ｈ．ｓｉｎｅｎｓｉｓ外，世界其它地区也有早期扭月贝类的报道，但多产于Ｌｌａｎｖｉｒｎ或更新的一些地层中，如发现于挪威Ｗｈｉｔｅｒｏｃｋ组的ＴｒｏｔｌａｎｄｅｌａｌｏｋｉＮｅｕｍａｎ（ＮｅｕｍａｎａｎｄＢｒｕｔｏｎ，１９７４），英国威尔士中部Ｌｌａｎｖｉｒｎ地层中的Ｍｕｒｉｎｅｌａｓｐ．，‘Ｍａｃｒｏｃｏｅｌｉａ’ｌａｎｄｅｉｌｏｅｎｓｉｓｅｌｏｎ?
Inner Mongolia, Wuhai City, about 25km south of the table mountain range Ordovs (earlylateArenig) Sandaan group at the bottom of the production of a primitive twisted shellfish Brachiopods, identified by the author, the Chinese shellfish (new species) (Hesperiniasinensissp .nov.). Systematic sectioning studies confirmed that it is the oldest known twisted shellfish to date, with its bilobal main protrusion slightly protruding behind the hinge edge, the lower and weaker hinge ridge to the side The trailing extension close to the hinged margin and other features indicate that this species belongs to the Strinkomenidae. The evolution of Pleuronectes to Twisted shellfish requires the creation of some morphologically evolved innate within the dorsal shell: the bilobed protuberances, a pair of hinged ridges that curve slightly toward the posterior side, the transverse ridges, As well as side partitions, all of these structural features, Hesperiniasinensissp. nov Therefore, this indicates that the differentiation of Twisted shellfish and Pleurotus ostreatus is earlier than that of late Arenig. In addition to H. sinensis, there are also early-stage molluscs in other parts of the world but are prolific in Llanvirn or later strata such as Trotlandelaloki Neuman (Neuman and Bruton, 1974) found in the Norwegian Whiterock Formation and Murinelasp in the Llanvirn Formation in central Wales, United Kingdom. , ’Macrocoelia’landeiloensiselon ?