论长城系微化石群的真核生物意义

本文主要以燕山地区长城系页岩相微化石群为基础,通过与现代生物形态标志的对比,论证了在18亿年前真核藻类即已繁盛发育,其中既包括有原始的绿藻和甲藻,也有低级的真菌,还可能有原始类型的褐藻,至于真核生物出现的时间则可追溯到古元古代。根据已知资料的综合,按体制阶段的发展规律给出了绿藻、甲藻以及褐藻的可能的各自发展路线,可供探讨藻类起源与演化时参考。

SIGNIFICANCE OF EUCARYOTIC ORGANISMS IN THE MICROFOSSIL FLORA OF CHANGCHENG SYSTEM

In this paper, it is considered that the appearance of eucaryotic organisms should bemuch earlier than 1 800 Ma based on data from the shale-facies microfossils of theChangcheng System in the Yanshan region. The morphological criteria for identification ofthe early fossil eucaryotes include large size,complex structure (with an inner body)and oth-er distinctive characters. Most of the microfossils are acritarchs. Among the fossil eucaryotesthere are not only unicellular planktons but also multicellular benthics,possibly belonging tothe original Chlorophyta,Pyrrophyta and the spores of Fungi. The microbiota,about 1 800Maold, are abundant,diverse and authentic,indicating that at the bottom of the Changcheng Sys-tem the eucaryotic algae have reached a prosperous stage in development and that the historyof unicellular eucaryotes must go back much earlier than 1 800Ma. As to the origin of eucary- otic cells,it may be inferred that the actual transition from Procaryotes to eucaryotes mighthave occurred in the Proterozoic Era, based on microfossil data of the Hutuo and AnshanGroups in North China,and the nearly 2 400Ma--old red beds. The present paper also discusses the Phylogeny of ancient eucaryotic algae,with the be-lief that in the Precambrian the oldest kinds of Chlorophyta and Pyrrophyta have existed andthe Phaeophyta might have one independent evolutionary lineage. The evolutionary series ofPrecambrian eucaryotic algae is shown in Fig. 2.