A group of related organisms but excluding some of their descendants that might be much different. (See monophyletic.)
A paraphyletic group is an incomplete clade - a clade from which one or more minor clades have been omitted. Such a group is recognised only by the absence of the homologues that define the excluded clades. For example, group AB above is paraphyletic; it can only be described by the absence of feature 3 - features 1 and 2 are present in group CD as well. In an evolutionary context, the term has a rather different meaning. It refers to a monophyletic group that does not include all the groups descended from a single common ancestor.
Referring to a group that does not include all the branches from the ancestral node.
a group of taxa derived from a single ancestral taxon, but which does not contain all the descendants of the most recent common ancestor.
A group of taxa that includes an ancestral taxon but not all descendants of that taxon - e.g. "fish" is a paraphyletic group because it does not include the other vertebrates, which undoubtedly also derive from the ancestral fish species.
a taxon consisting of a single ancestor but in which one or some of its descendants are omitted (e.g. Class Reptilia is a paraphyletic taxon because it excludes the birds)
