Paraphyly

Paraphyly is a characteristic of some groups of organisms and families of languages. In phylogenetics (a subfield of biology) and in linguistics, a group is said to be paraphyletic if it consists of all the descendants of the last common ancestor of the group's members minus a small number of monophyletic groups of descendants, typically just one or two such groups. For example, the group of reptiles, as traditionally defined, is paraphyletic: it contains the last common ancestor of the reptiles—including the extant reptiles as well as the extinct mammal-like reptiles—along with all descendants of that ancestor except for mammals and birds.