新疆西准噶尔晚泥盆世法门期的苔藓虫动物群及其形态特异性和古环境意义

Famennian(Late Devonian)bryozoans from western Junggar,Xinjiang,NW China:morphological specificities and palaeoenvironmental implications

本文重新研究了产自新疆西准噶尔晚泥盆世法门期洪古勒楞组和铁列克提组的苔藓虫动物群,重点关注其形态学特征和古生态学意义。该苔藓虫动物群由隐口目(Cryptostomata)、窗格苔藓虫目(Fenestrata),变口目(Trepostomata)和泡孔目(Cystoporata)组成。优势类群隐口目苔藓虫是具有中轴或中板的细枝状和双叶状群体。它们的虫室具有加厚的外区体壁,弯曲强烈的自虫室,数量众多的大虫室(metazooecia)或隐蔽虫室(tectizooecia),以及径向刺突和/或棘状刺突。多样化的异虫室、刺突、自虫室等结构,以及不同生长环境中的不同生态组合是新疆西准噶尔法门期苔藓虫成功演化的基础。洪古勒楞组下段和铁列克提组下部的苔藓虫动物群可以划分为三类生态组合(即:No. 1, No. 2和No. 3),代表前滨—近岸—远岸的沉积环境。其中,近岸环境的枝状—双叶状—网状苔藓虫组合的属种丰度、分异度最高。

This paper focuses on the morphology and palaeoecology of the latest Devonian bryozoans from western Junggar,northwestern China.Studied bryozoan materials,which contain diverse taxa of orders Cryptostomata,Fenestrata,Trepostomata,and Cysto porata,are based on museum specimens collected from the Hongguleleng and Tielieketi formations.Dominant cryptostome bryozoans possess characteristic delicately branched colonies with central axis or mesotheca,as well as bifoliate colonies.Specifically,these cryptostome bryozoans have thickened walls in exozone,strong bending of autozooecia chambers,abundant metazooecia or tectizooecia,and aktinotostyles and/or acanthostyles.Different combinations of heterozooecia,styles,forms of autozooecial chambers in colonies and different growth habits resulted in the successful evolution of the bryozoans from Xinjiang.In the lower member of the Hongguleleng Formation and the lower part of the Tielieketi Formation,three bryozoan associations,i.e.,bryozoan association No.1(Bal),No.2(Ba2),and No.3(Ba3)are proposed,indicating changes of environments from foreshore to offshore.Among them,the branched-bifoliate-reticulate colonies that lived in nearshore show higher abundance and diversity.