摘要
用统计方法分析了湖南邵东地区晚泥盆世Cyrtospirifer属的5个种群。证明腹壳指数的变化是连续的;腹壳基面特征的变化也是连续的,并与壳长成相关变异。中槽内壳线的特征可分为三种类型。槽内壳线型式,基面和壳长等特征可作为分种的依据。5个种群中标本的内部构造没有明显差别,许多外部特征是连续过渡的,所以Sinospirifer,Tenticospirifer和Hunanospirifer三亚属是Cyrtospirifer的同义名。作者还修订了该属的若干种。
Based on statistical methods the author has analyzed 5 populations of the genus Cyrtospirifer including a total of 140 specimens which were collected from two sections of the Upper Devoniau in the Shaodong area,Hunan Province.Various characters of each individual were measured and calculated(see Table 1—6).Grabau(1931)had emphasized that the shell index of the pedicle valve can be used as a criterion to identify a species.The result of statistics bears out that the distribution of the shell index in each population is a continuous variab1e and it is difficult to regard it as a criterion to identify a species.The form of the ventral cardinal area had been considered by Tien(1938)to be one of criteria to distinguish three subgenera:Sinospircfer(=Crrtospirifer),Tenticospirifer,and Hunanospirifer.However,the features of the cardinal area in 5 populations show continuous variatiou(Fig.3)and relation to shell length(Fig.5);therefore it is difficult to regard it as a criterion to identify a subgenus.The sinual costae in 5 populations can be divided into 3 types(Table 8 and Fig.7).The types of sinual costae,the forms of cardinal area and shell length can be treated as bases for identifying species.Tien(1938)pointed out that the shape and thickness of the cardinal plate in the brach?al valve is an important feature when he erected the subgenus Hunanospirifer.The author made a lot of series sections for studying interior structures(Fig.8),but did not find any obv?ous disparity in shape and thickness of cardinal plate.Taking into consideration the fact that the interior structures have no difference and most exterior characters exhibit continuous variations,the author believes that the subgenera Sinospirifer,Tenticospirifer,and Hunanospirifer are synonyms of the genus Cyrtospirifer.Several species amended are shown in the Table 9.
作者
徐桂荣
Xu Guirong(China University of Geosciences,Wuhan)
出处
《地质论评》
1988年第4期351-360,394,共11页
Geological Review
