A group of organisms that includes
their most recent common ancestor and some but not all of its
monophyletic; technically speaking, the distinction between
paraphyletic is not as clear as it might seem.) A taxon in which
either the ancestral species or some descendent species have
been removed by systematists to another group, usually because
of morphologic distinctiveness.
For example: "fish" is a paraphyletic group because it does not
include the other vertebrates, which undoubtedly also derive
from the ancestral fish species.