三叠纪小嘴贝类（Rhynchonellids）的表型—分支系统学

表型一分支系统学在方法上吸取数学系统学和分支系统学的优点,避免它们的缺点,是一种综合方法。本文以三叠纪小嘴贝类的47属为材料进行表型一分支系统学的研究。在性状状态分析的基础上,以距离量作为参数对47属作聚类分析,其主要结果获得各属之间总体相似程度,同时提出了对于分支分析十分有用语的信息,尤其关于祖一裔关系的信息。以近裔共性作为分支分析研究亲缘关系的主要标准,结合其它标准作出分支图。这种分支关系只是分类的一个依据,要作出合理的分类还必须研究各类间的性状状态的差异量,以确定分类的阶元。

PHENETIC - CLADISTIC SYSTEMATICS OFTRIASSIC RHYNCHONELLIDS

:The phenetic—cladistic systematics has absorbed those principal merits of the numerical and cladistic systematics respectively in methodology and has avoided their demerits in classification) therefore, so it is a synthetic systematics. The paper studies Triassic rhynchonellid classification to analyze the materials of 47 genera in light of the method of phenetic—cladistic systematics.11 characters are adopted to arrange three data matrices of genera according to the sequence of epoch (tables 3,4, 5)and three similarity matrices are listed by counting distance measures of each possible pair of genera. Degrees of overall similarites among genera are the principal results of cluster analysis, and at the same time, a number of informations which being usable for cladistic analysis are got from cluster analysis.In cladistic analysis synapomorphic character states are the chief criterion while other criteria are also considered by the paper. An integral cladogram (Fig. 5) got after cladistic analysis is one of the bases to proceeding classification. Otherwise, a reasonable classification need to make clear about divergent degrees of character states between each pair of comparing taxa in order to decide categorical rank for each taxon. A classification for Triassic rhynchonellids (table 8) is suggested in the paper.