polyphyletic

In biological classification, term describing a group of species that does not include its members' most recent common ancestor. Such groupings are avoided in most modern systems of classification. Examples are the marine mammals, trees, and algae.

If a group consists of all the descendants of a common ancestor plus the ancestor itself, it is called monophyletic; if it includes its members' common ancestor but not all of its descendants it is called paraphyletic. Distinguishing between such groups is an important part of the system of classification known as cladistics, which seeks to classify organisms into monophyletic groups, or clades.