Sauria is the clade containing the most recent common ancestor of Archosauria and Lepidosauria, and all its descendants. Since most molecular phylogenies recover turtles as more closely related to archosaurs than to lepidosaurs as part of Archelosauria, Sauria can be considered the crown group of diapsids, or reptiles in general. Depending on the systematics, Sauria includes all modern reptiles or most of them as well as various extinct groups.
The Phaethontiformes are an order of birds. They contain one extant family, the tropicbirds (Phaethontidae), and one extinct family Prophaethontidae from the early Cenozoic. Several fossil genera have been described, with well-preserved fossils known as early as the Paleocene. The group's origins may lie even earlier if the enigmatic waterbird Novacaesareala from the latest Cretaceous or earliest Paleocene of New Jersey is considered a tropicbird.
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.
Mirandornithes is a clade that consists of flamingos and grebes. Many scholars use the term Phoenicopterimorphae for the superorder containing flamingoes and grebes.
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 analysis 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 (Psittacopasserae), which together they form the clade Eufalconimorphae. The hawks and vultures occupy a basal branch in the clade Afroaves in their own clade Accipitrimorphae, closer to owls and woodpeckers.
Cariamiformes is an order of primarily flightless birds that has existed for over 60 million years. The group includes the family Cariamidae (seriemas) and the extinct families Phorusrhacidae, Bathornithidae, Idiornithidae and Ameghinornithidae. Though traditionally considered a suborder within Gruiformes, both morphological and genetic studies show that it belongs to a separate group of birds, Australaves, whose other living members are Falconidae, Psittaciformes and Passeriformes.
Australaves is a recently defined clade of birds, consisting of the Eufalconimorphae as well as the Cariamiformes. They appear to be the sister group of Afroaves. As in the case of Afroaves, the most basal clades have predatory extant members, suggesting this was the ancestral lifestyle; however, some researchers like Darren Naish are skeptical of this assessment, since some extinct representatives such as the herbivorous Strigogyps led other lifestyles. Basal parrots and falcons are at any rate vaguely crow-like and probably omnivorous.
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.
Telluraves is a recently defined clade of birds defined by their arboreality. Based on most recent genetic studies, the clade unites a variety of bird groups, including the australavians as well as the afroavians. They appear to be the sister group of the Phaethoquornithes.
Columbea is a clade suggested by genome analysis that contains Columbiformes, Pteroclidae (sandgrouse), Mesitornithidae (mesites) and Mirandornithes. Until their recent placement as the sister taxon to Passerea, in the last decade various genetic analysis found them to be in the obsolete clade Metaves.
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.
Otidimorphae is a clade of birds that contains the orders Cuculiformes (cuckoos), Musophagiformes (turacos), and Otidiformes (bustards) identified in 2014 by genome analysis. While the bustards seem to be related to the turacos, other genetic studies have found the cuckoos to be closer to the bustards than the turacos are.
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.
Cavitaves is a clade that contains the order Leptosomiformes and the clade Eucavitaves. The name refers to the fact that the majority of them nest in cavities.
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.
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.
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.
