Aequornithes

Not to be confused with Aequorlitornithes.

Aequornithes (/iːkwɔːrˈnɪθiːz/, from Latin aequor, expanse of water + Greek ornithes, birds), or core water birds,^[6] are defined in the PhyloCode as "the least inclusive crown clade containing Pelecanus onocrotalus and Gavia immer".^[3][7]

Aequornithes Temporal range: Early Paleocene–Holocene 62–0 Ma[1] PreꞒ Ꞓ O S D C P T J K Pg N Possibly an earlier origin based on molecular clock[2]
Shy albatross (Thalassarche cauta)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Clade:	Phaethoquornithes
Clade:	Aequornithes Mayr, 2010[3][4]
Clades
Gaviiformes Feraequornithes Sangster & Mayr, 2021[5] Austrodyptornithes Pelecanimorphae

The monophyly of the group is currently supported by several molecular phylogenetic studies.^{[8][9][10][11]}

Aequornithes includes the clades Gaviiformes, Sphenisciformes, Procellariiformes, Ciconiiformes, Suliformes and Pelecaniformes. It does not include several unrelated groups of aquatic birds such as flamingos and grebes (Mirandornithes), shorebirds, gulls, and auks (Charadriiformes), or the Anseriformes (waterfowl).

Based on a whole-genome analysis of the bird orders, the kagu and sunbittern (Eurypygiformes) and the three species of tropicbirds (Phaethontiformes) together styled as the Eurypygimorphae are the closest sister group of the Aequornithes,^[6] in a clade later named Phaethoquornithes.^[12]

Phylogeny

The cladogram below is based on Burleigh, J.G. et al. (2015)^[13] and Stiller et al. (2024)^[14] with some names after Sangster, G. & Mayr, G. (2021).^[5]

Aequornithes	Gaviiformes (loons/divers) Feraequornithes Austrodyptornithes Procellariiformes (albatrosses, shearwaters, and petrels) Sphenisciformes (penguins) Pelecanimorphae Ciconiiformes (storks) Pelecanes Suliformes (frigatebirds, gannets, cormorants, and darters) Pelecaniformes (pelicans, herons and ibises)

The clade Feraequornithes was named by Sangster & Mayr, 2021 to include the Pelecanimorphae and Procellariimorphae to the exclusion of the loons (Gaviiformes). They defined this clade in the PhyloCode as "the least inclusive clade containing Pelecanus onocrotalus and Procellaria aequinoctialis".^[5]