Biometrical Study of Morphological Variations of Microfossils in Time and Space

本研究旨在评价有孔虫、介形虫和硅藻等微化石在时空上的形态变化，阐明微化石在新生代的变迁。1988年，我们安装了一种新近改进的图像处理器，然后开始选择适合于测量和设置上述每一类群中种间和种内微化石形态变化的参数。在我们自第二年以来完成的工作中，尽管我们的研究最新进展将包含在收集的论文中，长达60页，附在“我们的研究结果报告”中：硅藻- Denticulopsis，一个生物地层学上重要的属，包括几个难以分配给其中一个或另一个的物种。这就要求生物计量学为它们的分类奠定有效的基础。因此，测量了每个波段的长度和宽度，以及计数室。结果表明：对于D. lauta来说，大多数带室数为奇数，最多为3个或5个；顶端假隔的排列有三种类型，出现在带的两端；在分析它们的生命周期时，室数和顶端假间隔的重要性更大；条带的长度和室数之间存在正相关关系，这表明细胞分裂不仅会导致条带长度的减少，而且还会导致其结构的改变。介形类——由于更新世期间海平面波动引起的变异事件，介形类物种的区域性灭绝可能涉及生态限制，这似乎反映在它们的矮化甲壳上，如Sinocytheridea latiovata。

The purpose of this research is to appraise the morphological variation of microfossils, including foraminifers, ostracodes and diatoms, in time and space, as well as to clarify the vicissitudes of microfossils through Cenozoic time. In 1988, we installed an image processor recently improved, and then have been engaged in selecting parameters suitable for measuring and setting off the morphological variations of microfossils among and within species in each of the above groups. Among pieces of our work accomplished since the second year are the following, although recent progress in our research will be contained in the collected papers, running into 60 pages, annexed to "the report on the results of our research" : Diatoms- Denticulopsis, a biostratigraphically important genus, includes several species which are difficult to be assigned to one or the others. This calls for biometrically laying foundations valid for their classification. In consequence, the length and width were measured, together with counting chambers, of each of the bands. The results show that with respect to D. lauta, the majority of bands have odd numbers of chambers, with a maximum number of 3 or 5 ; the existence of three types as to the arrangement of apical pseudosepta appearing at the ends of a band ; greater importance of chamber numbers and apical pseudosepta in analyzing their life cycles ; positive correlations between the length of and chamber numbers on bands, which indicate the possibility that the cell division gives rise not only to a reduction in the length of bands, but also to the modifications of their structures. Ostracodes- The regional extinction of stracode species due to a vicariance event caused by sea level fluctuations during the Pleistocene might involve ecological constraints which seem to be reflected on their dwarf carapaces, as exemplified by Sinocytheridea latiovata.