新疆巴楚地区晚奥陶世无颌类头甲的外部形态构造  

The External Morphological Structures of Agnathans Head Shields of Late Ordovician from Bachu County,Xinjiang

作　　者：王士涛[1] 郭宪璞[1] 

机构地区：[1]中国地质科学院地质研究所,北京100037

出　　处：《地质论评》2015年第6期1205-1210,共6页Geological Review

基　　金：国家自然科学基金资助项目(编号41372025);中国石化股份有限公司科技项目(编号YPh08110)的成果

摘　　要：本文主要报道采自新疆巴楚一间房剖面晚奥陶世恰尔巴克组紫红色瘤状泥质灰岩中具有外骨骼无颌类的头甲标本,其中一件头甲甲胄背部保存了清晰的眶孔、松果体,另外两件头甲腹部甲胄分别保存了口孔及鳃区鳃囊独立开向体外的6对外鳃孔等的外部形态构造,并初步讨论了其与国内外奥陶纪——泥盆纪具有外骨骼无颌类的异同关系。由于此次研究的头甲背部化石不具有志留纪——泥盆纪通常背甲背部前端具有的鼻垂体孔,而另外两件头甲腹部具有鳃区鳃囊独自开向体外的外鳃孔等构造特征,从而揭示了该地区晚奥陶世脊椎动物群具有的特殊性及独立性。这是自寒武纪发现以软体印模为主要特征的脊椎动物之后,首次在国内对前志留纪的具外骨骼的脊椎动物外部形态特征的详细报道。本研究对于了解、研究早期古脊椎动物的发生、演化,具有脊椎动物生物学依据及其分支系统的建立等重要意义。In this paper,there are three specimens of head shields possessing the external skeleton,collected from the purple-red muddy limestone of the Qiaerbake Formation,early-Late Ordovician,from the Yijianfang section of Bachu County,Xinjiang Autonomous Region. Among these specimens,the external morphological characteristics of the orbits( orb),pineal body( pi) are preserved on the one of the head shields( no. 7-19-8),but the armour plates are absent on another two head shields. There are oral( Or) and the six pairs of the external branchial openings( bro2 ~ 7) outward independently opening on ventral shield of the fish bodies. In addition,the differences and similarities between the Ordovician and the Silurian——Devonian agathans possessing the external skeleton are discussed. Since there is no the naso-hypophysial openings( nhypo) on the fossils,which possess six pairs of external branchial openings on the branchial region of the ventral aspect on the head shield. Therefore the Ordovician vertebrates of Bachu County should be a special and independent palaeotological vertebrate fauna. The paper is for the first time reporting the early vertebrate of the Ordovician possessing external skeleton,since Cambrian vertebrates fossils have no external skeleton in China up to now. This study is of great implication for understanding the early vertebrate's developing and evolution,and for establishing phylogenetic analysis on the basis of vertebrate biology.

关 键 词：无颌类 头甲外部形态 晚奥陶世 新疆巴楚 

分 类 号：Q915[天文地球—古生物学与地层学]