粤西云开地区中奥陶世双壳类动物群的发现及其意义初探

A Preliminary Study on Middle Ordovician Bivalves from Yunkai Area,Western Guangdong,South China

在粤西云开地区东冲组内发现以双壳类占绝对优势的中奥陶世动物群,包括双壳类:Praenucula cf.sharpei Babin and Gutierrez-Marco,P.sp.,Homilodonta regularis(Portlock),Similodonta similis(Ulrich),S.cf.cerys Cope,S.sp.,Trigonoconcha acuta Sanchez,Concavodonta sp.,Arcodonta sp.,Sthenodonta cf.eastii(Tata),S.sp.,Nuculites cf.cylindricus(Portlock),N.sp.,Phestia sp.,Cardiolaria?sp.,Inaequidens cf.davisi Pojeta and Gilbert-Tomlinson,I.sp.,Mytilarca?sp.,Cyrtodonta sp.,Modiolopsis spp.,Carminodonta sp.,Famatinodonta sp.等及若干未命名的新属,同层产出的还有三叶虫和腕足类等.双壳类化石个体小、丰度高、分异度高,以古栉齿类占绝对优势,该发现丰富了我国及世界中奥陶世双壳类动物群,为研究区中-上奥陶统的划分对比以及华南板块古地理重建增添了新的古生物学证据,特别是为研究双壳类的早期演化和奥陶纪早期双壳类辐射演化提供了关键信息.

Very abundant bivalves have been found from the Dongchong Formation,Yunkai area,Western Guangdong Province.The bivalve fauna consists of Praenucula cf.sharpei Babin and Gutierrez-Marco,P.sp.,Homilodonta regularis（Portlock）,Similodonta similis（Ulrich）,S.cf.cerys Cope,S.sp.,Trigonoconcha acuta Sanchez,Concavodonta sp.,Arcodonta sp.,Sthenodonta cf.eastii（Tata）,S.sp.,Nuculites cf.cylindricus（Portlock）,N.sp.,Phestia sp.,Cardiolaria？sp.,Inaequidens cf.davisi Pojeta and Gilbert-Tomlinson,I.sp.,Mytilarca？sp.,Cyrtodonta sp.,Modiolopsis spp.,Carminodonta sp.,Famatinodonta sp.and several un-named new genera,being featured by small individual size,high abundance and diversi-ty,palaeotaxodont assuming absolute superiority.Several Middle Ordovician trilobites and brachiopods occurred together with the bivalves.That fauna offers new data of Middle Ordovician bivalves,and will be helpful for better understanding of the early evolution of bivalves as well as the stratigraphic subdivision and correlations of Ordovician strata in the research area.