Kafanov A I
Izv Akad Nauk Ser Biol. 2007 Mar-Apr(2):163-70.
Cluster analysis was used to compare species composition of marine and brackish water bivalves in the Cenozoic deposits of the Russian Far East, Hokkaido, and California. Bivalvia species composition allows us to divide these deposits into two groups of clusters. The first group includes both extant and extinct species, while the second one is largely composed of extinct species. The drastic change in the bivalve species composition suggests that the base of the Uinin Horizon in the northern Sakhalin, Kuluven Horizon in the western Kamchatka, Tsubetsu Formation in eastern Hokkaido, and, possibly, the central part of the provincial Vaqueros Formation in California correspond to the Paleogene-Neogene boundary. The change in species composition was accompanied by the taxonomical diversity changes. At a higher level, the equitability of species richness among families significantly decreased.
聚类分析被用于比较俄罗斯远东地区、北海道和加利福尼亚新生代沉积物中海洋和咸淡水双壳贝类的物种组成。双壳贝类的物种组成使我们能够将这些沉积物分为两组聚类。第一组包括现存和已灭绝的物种，而第二组主要由已灭绝的物种组成。双壳贝类物种组成的急剧变化表明，萨哈林岛北部的乌宁阶底部、堪察加半岛西部的库卢文阶、北海道东部的津别组，以及可能加利福尼亚州省域瓦凯罗斯组的中部对应古近纪 - 新近纪边界。物种组成的变化伴随着分类多样性的变化。在更高层次上，科间物种丰富度的均匀度显著下降。
