贵州新元古代瓮安生物群中动物胚胎化石研究进展

The Embryo Fossils from the Neoproterozoic Weng'an Biota in Guizhou Province(South China)

瓮安生物群指产出于贵州瓮安磷矿地区新元古代埃迪卡拉纪陡山沱组(635～551Ma)上磷矿段的一个特殊磷酸盐化微体化石组合,主要由多细胞藻类、大型带刺疑源类和处于不同发育阶段的多种后生动物胚胎组成,并包括少量可能的后生动物幼虫和成体化石。瓮安生物群作为迄今为止世界上最古老的前寒武纪后生动物化石群,为探索后生动物的起源和早期演化历程提供了独一无二的实证记录。10余年来,瓮安生物群中动物胚胎化石的研究取得多项突破性进展,已确认至少5种不同卵裂方式的动物胚胎化石,胚胎化石分类从单纯的形态学分类向生物学分类转变,为揭示瓮安生物群中动物多样性提供了更多线索。同时,相关研究更新了繁盛于埃迪卡拉纪大型带刺疑源类生物属性的传统认识,并将之与有表面装饰的动物休眠卵(滞育胚胎)化石相联系。同步辐射X射线显微CT技术的应用成功解决了胚胎化石三维无损成像难题,为古胚胎学的发展带来了新的机遇。

The Ediacaran Weng＇an biota from the phosphorite of the upper Doushantuo Formation（635～551Ma） at Weng＇an, Guizhou Province（South China） consists of cyanobacteria, acritarchs, multicellular algae, and abundant metazoan eggs and embryos, together with few animal larvae and adults.These putative phosphatized animal embryo fossils with cellular structures preserved in three-dimensional structures have shed unprecedented paleontological light on the origin and early evolution of metazoans.Present paper reviews significant progresses of researches on the embryo fossils of the Weng＇an Biota during the past decade.Up to date, there are five types of embryos with different cleavage patterns that have been identified through various advanced techniques, especially the application of nondestructive 3D imaging by synchrotron radiation X-ray phase contrast microtomography（SRX-PC-μCT）.As a most challenging field in the frontier of paleontology, more significant discoveries and information about these early embryo fossils are expected through the investigations on new materials and applications of new techniques such as SRX-PC-μCT.Recent hypothesis that the large acanthomorphic acritarchs thieved during the same time of the Weng＇an Biota are the diapause embryos is an example.