分辨巨猿第一与第二臼齿的多元分析方法

DISTINGUISHING FIRST FROM SECOND MOLARS OF GIGANTOPITHECUS BY MULTIVARIATE ANALYSES

根据齿冠长度或宽度单一性状很难区分巨猿第一臼齿与第二臼齿。本文采用主成分分析方法,综合第一和第二上臼齿的齿冠长度、齿冠宽度和原尖长指数(新定义)等三个性状,显示存在有两个类型。合理的解释是它们分别代表第一上臼齿和第二上臼齿。下臼齿的分辨基于齿冠长度和齿冠宽度两个性状。在此二性状构成的坐标系中,第一与第二下臼齿各自的一系列椭圆代表一定比例的样本分布的范围。在此基础上得到区分此两种牙齿的判别直线。

In is difficult to distinguish Ml from M2 of Gigantopithecus through any single trait such as crown length and breadth, as showed by their distributions.The present paper applies the method of principal component analysis to distinguish first upper molars from second ones, and the variables used are crown length, crown breadth and protocone length index (newly defined). The results show the existence of two categories in M1,2. A reasonable explanation for this is that they represent M1 and M2 respectively. The role played by protocone length (mesiodistal diameter) to discriminate between M1 and M2 of Gigantopithecus becomes clear due to the principal component analysis. This trait is likely to be of significance for other high primates in the same aspect.The distinguishing of lower molars is based on the observation of the three Gigantopithecus mandibles with teeth as well as the over 100 isolated teeth. Two series of ellipses in the coordinate chart of crown length and breadth represent the ranges of different sample distribution probabilities of M1 and M2, respectively, and discsiminatory lines are drawn between M1 and M2.