Quasifusulina的旋壁构造及其在(竹蜓)类分类、演化中的意义

TEST WALL STRUCTURE OF QUASIFUSULINA AND ITS SIGNIFICANCE IN CLASSIFICATION AND EVOLUTION OF FUSULINID FORAMINIFERA

本文介绍作者利用扫描电子显微镜对(竹蜓)类Quasifusulina旋壁超微构造的初步研究结果。电镜观察表明,Quasifusulina旋壁的主要部分系由许多近等轴的方解石微粒构成,这些微粒有规律地叠置在一起,形成了一系列垂直于壳表、彼此相邻的方解石复合体。尽管其光学特征与蜂巢层和透明层颇为相似,但从构成旋壁的方解石微粒的形状、大小及排列和定向方式来看,Quasifusulina旋壁的超微构造既明显地有别于典型的蜂巢层,也不同于典型的透明层。为便于描述,作者建议将Quasifusulina旋壁的这种特殊构造称为“原蜂巢层”(prokeriotheca)。 根据电镜观察,Quasifusulina旋壁由原蜂巢层及不连续的内疏松层构成,它可能代表了?类有孔虫中一种独特的旋壁类型。这种旋壁构造在?类动物的分类及演化研究中可能具有重要意义。

An SEM examination on the test wall structures of Quasifusulina Chen,a common genusof Late Carboniferous and Early Permian fusulinids,has demonstrated that the primary wallstructure in the spirotheca of this genus is constructed by many fine calcite microgranulesroughly in isometric shapes. These microgranules are superimposed upon each other in thespirotheca,forming a series of small composite calcite columns perpendicular to the test sur-face. Although with an optical appearance similar to the keriotheca or diaphanotheca, thespirotheca of Quasifusulina is different from both the keriotheca and the diaphanotheca insuch ultrastructural features as the shapes,sizes and patterns of arrangement and orientationof the microgranules within the test wall. For convenience of description,the authors suggestto name this unique wall structure in the Quasifusulina the prokeriotheca,which was previ-ously described as the keriotheca or diaphanotheca. Study results also demonstrated that the spirotheca of Quasifusulina is composed of aprokeriotheca and a discontinuous inner tectorium. This kind of wall structure may representa peculiar type of spirotheca which is different from any other types of spirotheca in thefusulinid foraminifera recognized before. This paper also presents a brief discussion on thesignificance of this kind of spirotheca in the studies of classification and evolution of fusulinidforaminifera.