峡东奥陶纪末期笔石Tangyagraptus的厘定

A Revision of Late Ordovician Tangyagraptus (graptolite)in Eastern Yangtze Gorges Area

本文通过对峡东奥陶系五峰组笔石Tangyagraptus的系统采集和研究 ,认为该属以厘定为 3个种为宜 :Tangya graptustypicus,T .gracilis和T .remotus ,这三个种之间差别明显 ,前两者个体较小 ,但T .gracilis笔石枝较细 ,且宽度均匀 ,易与T .typicus区别 ,T .remotus一般个体较大 ,因第一个次生枝的着生位置远离胎管而得名。该属各种之间在海水中有不同的深度分带 。

On the basis of a systematic collection and study of Late Ordovician Tangyagraptus (graptolite) in eastern Yangtze Gorges area, the genus Tangyagraptus is reclassified into 3 species, i.e., Tangyagraptus typicus , T. gracilis and T. remotus . The rhabdosomes of the first two species are relatively small in size, and the slender and uniform stripes of T. gracilis make it easy to distinguish these two species. The rhabdosomes of T. remotus are relatively large in size and the secondary stripes from the primary stripes are always beyond the 8 th thecae-far away from the sicula. These three species occupy different depths in the water column (depth zonation) in the ocean, thus alleviating the competition between each other.