中国下泥盆统脊椎动物化石组合层序

本文综合了滇、黔、川、桂等地的一些早泥盆世地层剖面中的脊椎动物化石的出露情况,粗略地描绘出了早期脊椎动物演化的一般特征,归纳成三个发展阶段。并以此为依据,讨论了下泥盆统的分层与对比。

THE SEQUENCE OF EARLY DEVONIAN VERTEBRATE ASSEMBLAGES IN CHINA

Of the Chinese Early Devonian vertebrates three assemblages can be biostratigra-phically distinguished,in descending order as follows:3.Sanqiaspis-Asiaspis assemblage,which includes all members of Huanaspidaesuch as Sanqiaspis yielding from Posongchong of Zhaotong,N.E.Yunnan and the topof Pingyipu Formation in N.W.Szechuan,Asiaspis coming from the top of Lian-huashan Formation to the bottom of Nakaoling Formation in Guangxi,Szechuanaspisand Lungmenshanaspis coming from Pingyipu Formation in N.W.Szechuan andHuananaspis coming from Posongchong Formation in Wudin,E.Yunnan.As a wholethe horizon of the assemblage correspond roughly to Nakaoling Formation.2.Yunnanolepis-Qujinolepis aseemblage,its member are Yunnanolepis,Qujinolepis,Phymolepis and Zhanjilepis.Yunnanolepis and Qujinolepis occur chielfly in bothXitun Formation and Lianhuashan Formation of Guangxi,but Phymolepis andZhanjilepis occur only in Xitun Formation of Qujing,E.Yunnan.The age of theassemblage is probably Early Siegenian or Late Gedinnian and Early Siegenian.Amarked character of this assemblage is that Yunnanolepidae fossils are numerous andanother character is that they are associated with Eugaleaspis,Szeaspis,Asiacanthusand Youngolepis etc..1.Polybranchiaspis-Laxaspis assemblage which includes Polybranchiaspis,Laxas-pis,Diandongaspis and Dongfangaspis,most of them occur in Xishancun Formation ofQujing E.Yunnan besides few species.The aseemblage which was not found in thebottom of Lianhuashan Formation suggest that the sediment of Gedinnian were absentin Liujing,Guangxi.Three assemblages indicate three different revolutionary stages of Early Devoni-an vertebrates and correspond to Guijiatun Formation,Xitun Formation and Xish-ancun Formation respectively in horizon(see table 1).