Consider cladograms A and B above. These   cladograms differ in the hypothesized relationship of the turtle to other   reptiles (*). Cladogram A is the hypothesis that the turtle is sister taxon   to a clade, bird + crocodile (Archosauria). Cladogram A is the more   conventional alternative hypothesis that turtle is, instead, sister taxon to   all other reptiles (cladistically redefined to include birds in this course!).   This latter reptilian subclade is referred to as either Sauria or Diapsida,   depending on which name is preferred.

考虑上面的支序图A和B。这些支序结构的差别点在乌龟与其他爬行动物的聚类关系假设上。cladogram A假设，乌龟是鸟+鳄鱼（Archosauria）支系的一个姊妹群。cladogram   A是一个更为传统的假设，乌龟是所有其他爬行动物的姊妹分类群（在本课程中，所谓的其它爬行动物包括鸟类）.后一爬行动物分支根据命名被称为蜥蜴亚目或双孔亚纲。

Introduction to   Phylogeny: Hard or Soft Polytomies?

http://biology.fullerton.edu/biol404/phylo/polytomies.html