Hemiplasy helps explain high rates of apparent morphological convergence in neoavian birds

and holds fundamental implications for phylogenetic inference, fossil placement near the origin of Neoaves, and interpretations of morphological character state evolution. We highlight conserved polymorphism combined with rapid cladogenesis as a driver of the extensive patterns of apparent convergence in comparative morphological datasets and suggest that this phenomenon also underlies extensive patterns of homoplasy observed in other clades that have undergone rapid episodes of diversification, such as placental mammals.