sentences:  In the "PhyloCode", only a clade can receive a "phylogenetic definition", and this restriction is observed in the present article.However, it is also possible to create definitions for the names of other groups that are phylogenetic in the sense that they use only ancestral relations anchored on species or specimens.For example, assuming Mammalia and Aves (birds) are defined in this manner, Reptilia could be defined as "the most recent common ancestor of Mammalia and Aves and all its descendants except Mammalia and Aves".