The Gruiformes are an order containing a considerable number of living and extinct bird families, with a widespread geographical diversity. Gruiform means "crane-like".
The mesites (Mesitornithidae) are a family of birds that are part of a clade (Columbimorphae) that include Columbiformes and Pterocliformes. They are smallish flightless or near flightless birds endemic to Madagascar. They are the only family with more than two species in which every species is threatened.
Neoaves is a clade that consists of all modern birds with the exception of Palaeognathae and Galloanserae. Almost 95% of the roughly 10,000 known species of extant birds belong to the Neoaves.
Apodimorphae is a clade of strisorean birds that include the extant families Trochilidae (hummingbirds), Hemiprocnidae (treeswifts), Apodidae (swifts), and Aegothelidae (owlet-nightjars), as well as many fossil families. This grouping of birds has been supported in a variety of recent studies. There are two higher classification schemes that have been proposed for the apodimorph families. One is all strisorean birds are classified in the order Caprimulgiformes, while the other is the strisorean birds are split into several distinct orders. In this case Apodimorphae is a subclade of Strisores that includes the orders Aegotheliformes and the Apodiformes. A similar name for the group Daedalornithes has been used for the owlet-night-apodiform clade, there is a difference between the two names with Apodimorphae defined as the total-group and Daedalornithes defined as the crown group.
Aequornithes, or core water birds, are defined as "the least inclusive clade containing Gaviidae and Phalacrocoracidae".
The order Falconiformes is represented by the extant family Falconidae and a handful of enigmatic Paleogene species. Traditionally, the other bird of prey families Cathartidae, Sagittariidae (secretarybird), Pandionidae (ospreys), Accipitridae (hawks) were classified in Falconiformes. A variety of comparative genome analyses published since 2008, however, found that falcons are part of a clade of birds called Australaves, which also includes seriemas, parrots and passerines. Within Australaves falcons are more closely related to the parrot-passerine clade than they are to the seriemas. The hawks, vultures and owls are placed in the clade Afroaves.
Eurypygiformes is an order formed by the kagus, comprising two species in the family Rhynochetidae endemic to New Caledonia, and the sunbittern from the tropical regions of the Americas. Its closest relatives appear to be the tropicbirds of the tropical Atlantic, Indian, and Pacific oceans.
Metaves is a controversial group proposed by Fain & Houde (2004) and later rescued on the studies of Ericson et al. (2006) and Hackett et al. (2008). This group consists of several lineages that diversified early in Neornithes evolution. These lineages include Strisores, pigeons, sandgrouses, mesites, Eurypygae, tropicbirds and Mirandornithes, but the exact members of Metaves and their relationship differs between those studies, and the group is only supported by the β-fibrinogen gene.
Strisores, sometimes called nightbirds, is a clade of birds that includes the living families and orders Caprimulgidae, Nyctibiidae (potoos), Steatornithidae (oilbirds), Podargidae (frogmouths), Apodiformes, as well as the Aegotheliformes (owlet-nightjars) whose distinctness was only recently realized. The Apodiformes and the Aegotheliformes form the Daedalornithes.
Australaves is a clade of birds, defined in 2012, consisting of the Eufalconimorphae as well as the Cariamiformes. They appear to be the sister group of Afroaves.
Afroaves is a clade of birds, consisting of the kingfishers and kin (Coraciiformes), woodpeckers and kin (Piciformes), hornbills and kin (Bucerotiformes), trogons (Trogoniformes), cuckoo roller (Leptosomiformes), mousebirds (Coliiformes), owls (Strigiformes), raptors (Accipitriformes) and New World vultures (Cathartiformes). The most basal clades are predatory, suggesting the last common ancestor of Afroaves was also a predatory bird.
Passerea is a clade of neoavian birds that was proposed by Jarvis et al. (2014). Their genomic analysis recovered two major clades within Neoaves, Passerea and Columbea, and concluded that both clades appear to have many ecologically driven convergent traits.
Eurypygimorphae or Phaethontimorphae is a clade of birds that contains the orders Phaethontiformes (tropicbirds) and Eurypygiformes recovered by genome analysis. The relationship was first identified in 2013 based on their nuclear genes. Historically these birds were placed at different parts of the tree, with tropicbirds in Pelecaniformes and the kagu and sunbittern in Gruiformes. Some genetic analyses have placed the eurypygimorph taxa in the controversial and obsolete clade Metaves, with uncertain placement within that group. More recent molecular studies support their grouping together in Eurypygimorphae, which is usually recovered as the sister taxon to Aequornithes within Ardeae.
Phaethoquornithes is a clade of birds that contains Eurypygimorphae and Aequornithes, which was first recovered by genome analysis in 2014. Members of Eurypygimorphae were originally classified in the obsolete group Metaves, and Aequornithes were classified as the sister taxon to Musophagiformes or Gruiformes.
Columbimorphae is a clade discovered by genome analysis that includes birds of the orders Columbiformes, Pterocliformes (sandgrouse), and Mesitornithiformes (mesites). Previous analyses had also recovered this grouping, although the exact relationships differed. Some studies indicated a sister relationship between sandgrouse and pigeons while other studies favored a sister grouping of mesites and sandgrouse instead.
Columbaves is a clade that contains Columbimorphae and Otidimorphae discovered by genomic analysis by Prum et al. (2015). This conflicts with the Columbea and Otidae hypotheses which Mirandornithes are the sister taxon to Columbimorphae and Cypselomorphae the sister taxon to Otidimorphae, respectively, found by Jarvis et al. (2014). Neither hypothesis supports the two subdivisions of Metaves and Coronoaves as previous studies had found.
Inopinaves is a clade of neoavian birds recovered in a compressive genomic systematic study using nearly 200 species in 2015. It contains the clades Opisthocomiformes (hoatzin) and Telluraves ; the study shows that the hoatzin diverged from other birds 64 million years ago. Previous studies have placed the hoatzin in different parts of the bird family tree; however, despite its unusual morphology, genetic studies have shown the hoatzin is not as primitive or as ancient as once thought; it could be a very derived bird that reverted to or retains some plesiomorphic traits.
Vanescaves is a probable clade of strisorean birds that include the clades Steatornithiformes, Nyctibiiformes, Podargiformes (frogmouths), and Apodimorphae. Some molecular studies do support the grouping of these birds, others offer conflicting positions of the non-apodimorphaean strisoreans. In 2019 the authors Chen et al. performed a combined analysis using 2289 ultra-conserved elements [UCEs], 117 morphological characters from extant and fossil taxa found support in this clade. The authors then proposed to name this group, which its meaning is Latin for "vanish birds" in reference to the disparate nature of their geographic distribution, as well as to the poem "A Route of Evanescence" by the American poet Emily Dickinson which features a hummingbird as the main subject. In 2020 Chen & Field named the two major subclades of this group, with Sedentaves and Letornithes for their crown-groups.
Hieraves is a clade of telluravian birds named by Wu et al. (2024) that includes the orders Strigiformes (owls), Cathartiformes, and Accipitriformes. In the past, either owls, New World vultures, and hawks were found to be basal outgroups with respect to Coraciimorphae inside Afroaves, or Accipitriformes and Cathartiformes were recovered as a basal clade in respect to the rest of the members of Telluraves. Houde and Braun (2019) found support for Hieraves, but they were found to be the sister group to Coraciimorphae and Australaves. The analysis of Wu et al. (2024) has found Hieraves to be the sister clade to Australaves. Stiller et al. (2024) found Hieraves to be basal to Afroaves.
Litusilvanae is a proposed clade of birds, position as the sister clade to Aequorlitornithes. This clade comprises Gruimorphae and Strisores. While different lines of evidence from molecular, morphology and the fossil record has found support in the clades Gruimorphae and Strisores Wu et al. (2024) was the first to find support in such a novel sister group relationship between these two taxa.
