论Yunnanellina与Eocoelia的内部构造

On the Internal Structure of Yunnanellina and Eocoelia(Brachiopoda)

对湘中大量Ｙｕｎｎａｎｅｌｌｉｎａ标本的形态系统研究后，发现许多个体在隔板槽前上方具有盖板，横向和纵向上，盖板都有不同程度的变化，但纵向上，隔板槽和盖板形态在不同剖面有着相同的规律性变化，可用于详细分层和对比。对Ｙｕｎｎａｎｅｌｌｉｎａ和早志留世Ｅｏｃｏｅｌｉａ形态比较后，本文提出内部构造与外部形态是相辅相成的，外部形态变异大，内部构造变异也就大，反之亦然。

Transverse serial sections of 36 specimens of various“species”of Yun-nanellina from central Hunan reveal that many specimens possess a cover plate(=connectivum in Sartenaer,1969)anteriorly over the septalium. Stratigraphically,the septalium from the lower part is always broad and rounded;the cover plate varies greatly in morphology,especially in“Y. uniplicata”;but all specimens of“Y. han-buryi”do not possess a cover plate. In the middle part,Yunnanellina possess a nar row and deep septalium;the cover plate is horizontally extended,but becomes her-ring-bone shaped upwards in“Y,uniplicata”.In the upper,the septalium is V or U shaped,partly coveredban incomplete cover plate. The systematic variation of the above described internal structure may be used for stratigraphic correlation of dif-ferent sections.Study on both Yunnanellina and Eocoelia shows that the internal structure of a brachiopod is consistent with its external morphology.When the external morpholo-gy is greatly varied,the internal structure is also greatly varied; when the external morphology is stable,the internal structure is also stable.This indicates that cau-tion must be taken in using internal features to establish new taxa for those speci-mens of great variability in external morphology.