Anatoidea

Anseriformes Temporal range: Late Cretaceous-Holocene, 68–0 Ma PreЄ Є O S D C P T J K Pg N
Magpie goose, Anseranas semipalmata
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Superorder:	Galloanserae
Order:	Anseriformes Wagler, 1831
Extant families
Anhimidae Anseranatidae Anatidae
Range of the waterfowl and allies
Synonyms
Anserimorphae

Anserimorphae

Anseriformes is an order of birds that comprises about 180 living species in three families: Anhimidae (the screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which includes over 170 species of waterfowl, among them the ducks, geese, and swans. In fact, these living species are all included in Anatidae except for the three screamers and the magpie goose. All species in the order are highly adapted for an aquatic existence at the water surface. The males, except for the screamers, also have a penis, a trait that has disappeared in Neoaves. All are web-footed for efficient swimming (although some have subsequently become mainly terrestrial).

The earliest known Anseriform is the recently discovered Vegavis, which lived during the Cretaceous period. It is thought that the Anseriformes originated when the original Galloanserae (the group to which Anseriformes and Galliformes belong) split into the two main lineages. The extinct dromornithids may possibly represent early offshoots of the anseriform line, if they aren't stem-Galliformes instead, and so maybe Gastornis (if it is an Anseriform). The ancestors of the Anseriformes developed the characteristic bill structure that they still share. The combination of the internal shape of the bill and a modified tongue acts as a suction pump to draw water in at the tip of the bill and expel it from the sides and rear; an array of fine filter plates called lamellae traps small particles, which are then licked off and swallowed.