It falls outside the scope of the formal taxonomic categories. 它不屬于正規(guī)植物分類學(xué)的分類階元的范疇。
For instance, all birds and reptiles are believed to have descended from a single common ancestor, so this taxonomic grouping is called monophyletic. 例如，所有的鳥類和爬行動(dòng)物被認(rèn)為是從一個(gè)單一的共同祖先傳下來的，因此這個(gè)分類學(xué)的分組被稱為單系類群。