A paraphyletic group is a clade which does not include all members within it. It excludes a point of divergence from a node, which may lead to the exclusion of a taxon on a branch or an entire monophyletic group.
A paraphyletic group is often the result of incomplete evidence. Historical examples of paraphyletic groups include the exclusion of Aves, a modern-day class which was previously identified as a major clade under the tetrapod superclass. Recent evidence shows that members of Aves evolved from the Dinosauria class, who are grouped under the disputed clade Reptilia. Previous phylogenies of Reptilia as a class are paraphyletic because they exclude classes such as Dinosauria and Aves.