Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae, Anseranatidae, and Anatidae, the largest family, which includes over 170 species of waterfowl, among them the ducks, geese, and swans. Most modern species in the order are highly adapted for an aquatic existence at the water surface. With the exception of screamers, males have penises, a trait that has been lost in the Neoaves. Due to their aquatic nature, most species are web-footed though this one is not.
The screamers are three South American bird species placed in family Anhimidae. They were thought to be related to the Galliformes because of similar bills, but are more closely related to Anseres, i.e., ducks, and the magpie goose. The clade is exceptional within the living birds in lacking uncinate processes of ribs. The three species are: The horned screamer ; the southern screamer or crested screamer ; and the northern screamer or black-necked screamer.
The Oxyurini are a tribe of the duck subfamily of birds, the Anatinae. It has been subject of considerable debate about its validity and circumscription. Some taxonomic authorities place the group in its own subfamily, the Oxyurinae. Most of its members have long, stiff tail feathers which are erected when the bird is at rest, and relatively large, swollen bills. Though their relationships are still enigmatic, they appear to be closer to swans and true geese than to the typical ducks. The highest diversity is found in the warmer parts of the Americas, but at least one species occurs in a major part of the world.
Anseranatidae, the magpie-geese, is a biological family of waterbirds. The only living species, the magpie goose, is a resident breeder in northern Australia and in southern New Guinea.
Gastornis is an extinct genus of large flightless birds that lived during the mid-Paleocene to mid-Eocene epochs of the Paleogene period. Fossils have been found in Europe, Asia and North America, with the remains from North America originally assigned to the genus Diatryma.
The pygmy geese are a group of very small "perching ducks" in the genus Nettapus which breed in the Old World tropics. They are the smallest of all wildfowl. As the "perching ducks" are a paraphyletic group, they need to be placed elsewhere. The initially assumed relationship with the dabbling duck subfamily Anatinae has been questioned, and it appears they form a lineage in an ancient Gondwanan radiation of waterfowl, within which they are of unclear affinities. An undescribed fossil species from the late Hemphillian of Jalisco, central Mexico, has also been identified from the distal end of a tarsometatarsus. It is only record of the genus in the New World.
The southern screamer is a species of bird in family Anhimidae of the waterfowl order Anseriformes. It is found in Argentina, Bolivia, Brazil, Paraguay, Peru, and Uruguay.
The northern screamer is a Near Threatened species of bird in family Anhimidae of the waterfowl order Anseriformes. It is found in Colombia and Venezuela.
Vegavis is a genus of extinct bird that lived during the Late Cretaceous of Antarctica, some 68 to 66 mya. Among modern birds, most studies show that Vegavis is most closely related to ducks and geese (Anatidae), but it is not considered to be a direct ancestor of them, although other studies question these results.
Presbyornis is an extinct genus of anseriform bird. It contains two unequivocally accepted species; the well-known P. pervetus and the much lesser-known P. isoni. P. pervetus was approximately the size and shape of a goose, but with longer legs; P. isoni, known from a few bones, was much larger, more than swan-sized. Other fossils, more doubtfully assigned to this genus, are also known.
Presbyornithidae is an extinct group of birds with a global distribution. They had evolved by the late Cretaceous period and became extinct during the early Miocene. Initially, they were believed to present a mix of characters shown by waterbirds, shorebirds and flamingos and were used to argue for an evolutionary relationship between these groups, but they are now generally accepted to be waterfowl closely related to modern ducks, geese, and screamers.
Anatalavis is genus of prehistoric birds related to ducks and geese, perhaps in particular the magpie-goose. Alternatively, it may be a more basal lineage of Anserimorphae distinct from the living waterfowl, similar or even related to the roughly contemporary Conflicto antarcticus from the Danian of Antarctica.
Gastornithiformes were an extinct order of giant flightless fowl with fossils found in North America, Eurasia, possibly Australia. Members of Gastornithidae were long considered to be a part of the order Gruiformes. However, the traditional concept of Gruiformes has since been shown to be polyphyletic.
Teviornis is a genus of extinct birds. One species has been described, T. gobiensis. It lived in the Maastrichtian stage at the end of the Late Cretaceous period, some 70 million years ago. It is known from fossils collected from the Nemegt Formation of Gobi, south Mongolia.
Lithornis is a genus of extinct paleognathous birds. Although Lithornis was able to fly well, their closest relatives are the extant tinamous and ratites.
Paracathartes is a genus of extinct bird from the Wasachtian horizon of lower Eocene Wyoming. One species, Paracathartes howardae has been described.
The Odontoanserae is a proposed clade that includes the family Pelagornithidae and the clade Anserimorphae. The placement of the pseudo-toothed birds in the evolutionary tree of birds has been problematic, with some supporting the placement of them near the orders Procellariformes and Pelecaniformes based on features in the sternum.
Garganornis is an extinct genus of enormous flightless anatid waterfowl from the Late Miocene of Gargano, Italy. The genus contains one species, G. ballmanni, named by Meijer in 2014. Its enormous size is thought to have been an adaptation to living in exposed, open areas with no terrestrial predators, and as a deterrent to the indigenous aerial predators like the eagle Garganoaetus and the giant barn owl Tyto gigantea.
Conflicto antarcticus is a species of stem waterfowl whose fossils were found in the early Paleocene López de Bertodano Formation of Antarctica, the only species of its genus and the family Conflictonidae. It is characterized by it slender body and long legs, yet possesses a duck-like bill which indicates the form of beak evolved early in Anseriformes.
Wunketru is an extinct genus of waterfowl from the Eocene Las Flores Formation of Chubut Province, Argentina. The genus contains a single species, W. howardae, known from a partial skeleton previously classified as a species of Telmabates.
