华南寒武纪奥斯坦型化石研究进展

A REVIEW OF PROGRESS ON CAMBRIAN ORSTEN-TYPE FOSSILS IN SOUTH CHINA

传统的奥斯坦型(Orsten-type)化石是指三维磷酸盐化的、以软躯体保存为主的、微型蜕皮动物化石。它们代表着早寒武世到早奥陶世浅海小型底栖生物群中的蜕皮动物,是其它类型的保存方式(如布尔吉斯页岩型)难以保存的。奥斯坦型化石在西方有近半个世纪的研究历史,但是在中国却起步较晚,直到2005年才首次报道。中国的奥斯坦型化石在四个剖面的相关层位有产出,即湘西王村剖面上寒武统排碧阶、滇北硝滩剖面下寒武统第三阶、陕南张家沟剖面和川北新立剖面的下寒武统幸运阶。报道的化石类群包括丰富的甲壳动物Phosphatocopida,最古老的真甲壳动物,最古老的环神经动物,动吻动物门第一个化石属种,等等。虽然研究历史短,中国的奥斯坦型化石在揭示甲壳动物、环神经动物及蜕皮动物的起源和早期演化方面展现了重要的价值。

Traditional Orsten-type fossils refer to three-dimensionally phosphatized, mainly soft-bodied, and microscopic fossil ecdysozoans. They represent the ecdysozoans of the meiofauna in the shallow water of Cambrian seas from early Cambrian to early Ordovician, and they are almost lacking in the lagerstatten of other types of preservation, e. g, the Burgess Shale-type preservation. Orsten-type fossils have been studied for nearly half a century in the West, but in China it was not until 2005 that the Orsten-type fossils were reported for the first time. In South China, Orsten-type fossils are reported in key horizons from four localities, i. e, upper Cambrian Paibian Stage at Wangcun section in Western Hunan, lower Cambrian Stage 3 at Xiaotan section in northern Yunnan, lower Cambrian Fortunian Stage at Zhangjiagou section in southern Shaanxi and Xinli section in northern Sichuan. Orsten-type fossils from South China include abundant phosphatocopid crustaceans, the oldest known crown-group crustaceans, the oldest known cyeloneuralian worms, and the first fossil record of Kinorhyncha, etc. Although with a short research history, the Orsten-type fossils in South China have exhibited important significance in uncovering the origin and early evolu- tion of crustaceans, cycloneuralians and ecdysozoans as a whole.