Feraequornithes: a name for the clade formed by Procellarii formes, Sphenisciformes, Ciconiiformes, Suliformes and Pelecaniformes (Aves)

Recent genomic data sets have resolved many aspects of higher-level phylogenetic relationships of birds. Eleven phylogenomic studies provide congruent support for a clade formed by Procellariiformes, Sphenisciformes, Ciconiiformes, Suliformes and Pelecaniformes. This clade is here named ‘Feraequornithes’ following the rules and requirements of the PhyloCode.

These studies have further shown that 'Pelecaniformes ' and 'Ciconiiformes', as traditionally circumscribed (e.g. Storer 1971;Howard and Moore 1991), represent non-monophyletic groups. There is now robust evidence that herons, ibises, pelicans and allies form a clade; that the frigatebirds, darters, cormorants, gannets and boobies form another clade, and that the storks represent a third clade. These three clades are now known as Pelecaniformes, Suliformes and Ciconiiformes, respectively (Yuri et al. Vertebrate Zoology 71, 2021, 49-53 | DOI 10.3897/vz.71.e61728 Copyright George Sangster. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 2013; Mayr 2017; Kimball et al. 2019;Kuhl et al. 2021), although Cracraft (2013) used the name Pelecaniformes for a group that combines all three clades. A sister group relationship of Procellariiformes and Sphenisciformes is also well-supported (Hackett et al. 2008;McCormack et al. 2013;Jarvis et al. 2014;Burleigh et al. 2015;Kuramoto et al. 2015;Prum et al. 2015;Reddy et al. 2017;Kimball et al. 2019;Kuhl et al. 2021), and this clade has been named Procellariimorphae (Livezey and Zusi 2007).
Evidence for a clade formed by Procellariiformes, Sphenisciformes, Ciconiiformes, Suliformes and Pelecaniformes consists of multiple phylogenomic data sets generated in eleven studies, and is summarized in Table  1. This clade has not been named yet, unlike many other novel clades that are now widely supported (Sangster 2005a(Sangster , 2005bMayr 2011;Suh et al. 2011;Ericson 2012;Yuri et al. 2013;Prum et al. 2015).
The stability of taxonomic names above the superfamily rank has long been problematic because their availability and priority was not governed by any nomenclatural code. In the mid 1980s, taxonomists begun proposing, discussing and using phylogenetic definitions for clade names (e.g. Gauthier 1986;Rowe 1987;De Queiroz and Gauthier 1992;Bryant 1994;Lee 1996;Padian et al. 1999). This grew out of the recognition that the current rank-based systems of nomenclature (e.g. ICZN 1999) are poorly suited to regulate the names of clades. These discussions about phylogenetic nomenclature have led to the development of the PhyloCode which went through several preliminary versions that appeared online between 2000 and 2019. The publication of the PhyloCode (v6; Cantino and De Queiroz 2020), which came into effect in June 2020 with the publication of the companion volume Phylonyms (De Queiroz et al. 2020) and the RegNum online database (Cellinese and Dell 2020), now provides an opportunity to formalize and stabilize clade names. The PhyloCode provides rules for the express purpose of naming clades through explicit reference to phylogeny (Cantino and De Queiroz 2020). The purpose of this note is to define a name for the clade formed by Procellariiformes, Sphenisciformes, Ciconiiformes, Suliformes and Pelecaniformes following the rules and requirements of the PhyloCode. Etymology. Coined from a combination of Aequornithes with the Latin adverb fere, meaning "almost" or "near", in reference to the fact that the clade includes almost all Aequornithes except Gaviiformes.
Reference phylogeny. For the purpose of applying the definition of Feraequornithes, Figure 3 in Kuhl et al. (2021) should be regarded as the primary reference phylogeny. Figure 1 in Prum et al. (2015) may be regarded as a secondary reference phylogeny.
Diagnostic apomorphies. Members of this clade possess long, slit-like nostrils in juveniles (Mayr 2017). These are absent in extant Sphenisciformes and Procellariiformes, but occur in adults of long-beaked fossil stem group Sphenisciformes (Ksepka et al. 2008;Mayr et al. 2017). Possibly correlated with the latter trait, the beak of adult birds of most representatives of the clade exhibits furrows along its lateral surfaces, which begin at the rostral end of the nostril (these furrows are absent in the Ciconiidae and weakly developed in the Ardeidae). Kuramoto et al. (2015) listed eight apomorphic retroposons (Chicken Repeat 1 insertions), which are found on chromosomes 1, 1A, 2, 5 and 20.