Phylogenetic definitions for 25 higher-level clade names of birds

Knowledge of the higher-level phylogenetic relationships of birds has grown substantially during the past two decades due to the application of genomic data. However, the nomenclature of higher-level taxa has not become more stable, due to the lack of regulation of taxon names above the level of superfamily by the ICZN, and the usage of rank-based nomenclature, which is not tied to clades in a phylogeny. Lack of regulation and the instability of rank-based nomenclature impede effective communication among systematists. We review support for higher-level avian clades using a set of 10 phylogenomic data sets, and identify clades that are supported by congruency of at least four of these. We provide formal definitions of the names of these clades based on the rules of the recently published PhyloCode. The names of 25 clades are here defined using minimum-crown-clade (n = 23), minimum-clade (n = 1) and maximum-crown-clade (n = 1) definitions. Five new names are introduced here: Dinocrypturi, Pteroclimesites, Musophagotides, Phaethoquornithes and Pelecanes. We also review diagnostic apomorphies of the relevant clades, and identify known synonyms and homonyms. By establishing a formal link between higher-level taxon names and well-supported phylogenetic hypotheses, our phylogenetic definitions will provide a solid basis for the stabilization of avian higher-level nomenclature.

Automated summary

The knowledge of higher-level phylogenetic relationships of birds has significantly increased in the past two decades with the application of genomic data. However, the nomenclature of higher-level taxa remains unstable due to the lack of regulation by the ICZN and the use of rank-based nomenclature. Lack of regulation and instability impede effective communication among systematists. This study reviews support for avian clades using phylogenomic data sets and provides formal definitions of their names based on the rules of the PhyloCode, aiming to stabilize avian higher-level nomenclature.