中国晚前寒武纪的宏体化石概观

SOME ASPECTS OF STUDIES ON LATE PRECAMBRIAN MACROFOSSILS IN CHINA

本文综述了目前中国晚前寒武纪地层中所发现的宏体化石,从18亿年起直到6亿年左右。蓟县剖面高于庄组(14亿年)中发现Grypanta等大化石,再次证明生物演化大阶段的世界性。包括后生动物实体化石在内的淮南生物群可能是前冰期的,也就是先伊迪卡拉期的。震旦纪晚期的西陵峡生物群,现有伊迪卡拉期的典型分子,又有丰富的蠕虫管和高级的红藻、绿藻类。蠕虫管的大量出现预告了带硬部动物时代的到来。

In accordance with recent discoveries in world, macrofossils have been proved real repre-entatives of Middle and Upper Proterozoic life. The records of macroscopic body fossils can be traced back to about 1000 Ma ago (Hofmann and Chen, 1981; Yan Yu-Zhong, 1985).The Grypania et al. macrofossils from Gaoyuzhuang Formation in Jixian section, which are very similar to those from Greyson shale of Ravalli Group in Belt Supergroup of North America, bear the evidence of that major evolutionary stages of life are of cosmopolitan natu-re. Therefore, the; sediments deposited since at least 1400 Ma become the objects to be searched for macrofossiis..Pre-Ediacaran Hainan Biota is made of several kinds of macrofossils: Chuarid, Tawuid, Vendotaenid, worm fossils, and possible Longfengshanid with primary differentiation of the tissures. These macrofossils are similar to those from pre-glaciation Little Dal Group in Canada except for worm fossils.. In our knowledge of precambrian palaeontology, it can be a breakthrough that animal body fossils are found in pre-glaciation sediments. The worms evidently had coelom and proboscis (that implies the cephalozition). The Biota constructed a new ecosystem and bore longer food chain. But the diversity of plant and animal life is still low, their size is relatively small. All these mean that the evolutionary level at that time is ower than that for Sinian-Ediacaran.In the Yangtze Platform, Charnia dengyingensis found by Ding et Chen in Upper Sinian is one of the typical members of Ediacaran-Vendian biota. With respect to metaphyta. Ven-dotaenid is abundant in number, and the green algal fossils with three orders of branching and calcareous red algae are found. These metaphyta should build up submarine grassland which was a new niche for animal life. There were abundant worm tubes similar to Cloudina which were originally calcareous or secondarily silicified and pyritized. It is very interesting that this kind of fossils is reported from correspondents in Mexico, Iran, Brazil and Southwest Africa, and then there may be some potential for stratigraphic comparison. It signified that the times of animal life with hard parts would come soon. Additionally, we know a variety of trace fossils. The first assemblage of small shelly fossils, Protohertzina-Anabarites, occurred in overlying strata. The evolutionary process from soft body to certain hard parts in animal life is a gradually improving one. Recently, discovery of medusa-like Fauna is made in North China (Liaoning Peninsula). It soems that Chinese macrofossil succession in Middle and Upper Proterozoic is perfect.The future for studies on the macrofossils in Precambrian will be bright because the Middle and Upper Proterozoic sediments are well-exposed and widespread in China.