陕南寒武纪西乡生物群中Anabarites对称性演化研究

阿纳巴管(Anabarites)是寒武纪早期一类形态独特的管栖生物,其横切面的轮廓多样,但所有形态都是"3"的倍数。陕南梅树村期西乡生物群产出大量磷质Anabarites,根据管体上纵槽出现的数目和级别,确认Anabarites可分辨出三种对称类型:A型为仅具有三条一级纵槽的三辐射对称类型、B型具有三条一级纵槽和一条二级纵槽类型、C型具有三条一级纵槽和两条二级纵槽。其中B型、C型是从三辐射到六辐射对称之间的过渡类型,为新发现的对称形式。本文以上述三种类型Anabarites为研究材料,对Anabarites对称性演化途径进行了探索性研究,对寒武纪大爆发之初动物的对称性起源演化研究提供了重要证据。

RESEARCH ON THE SYMMETRICAL EVOLUTION OF ANABARITESFROM THE CAMBRIAN XIXIANG BIOTA IN SOUTHERN SHAANXI PROVINCE

Anabarites is a kind of unique Early Cambrian tubicolous animal.There are various outlines of its crosssection,but all of them are multiples of three.We have found a great amount of phosphatic Anabaritesfrom the Early Cambrian(Meishucunian)in the Xixiang Biota,Xixiang County,Shaanxi Province,China.Accroding to the number and level of longitudinal grooves on the tube,we confirmed that three symmetry types can be distinguished from those fossils:A-type only has three first-order grooves;B-type has three first-order grooves and one second-order groove;C-type has three first-order grooves and two second-order grooves.The B-type and C-type are the transition types from three-symmetry(Anabarites trisulcatus)to six-symmetry(Anabarites sexalox),which were newly discovered.In this paper,we studied these three types of Anabarites to explore the symmetry evolutionary approach,which provided important evidence for the studies of symmetry evolution of animal at the beginning of the Cambrian explosion.