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Anseriformes

(Order)

Overview

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The order Anseriformes contains about 150 living of birds in three extant families: the Anhimidae (the screamers), Anseranatidae (the Magpie-goose), and the Anatidae, which includes over 140 species of waterfowl, among them the ducks, geese, and swans.

All species in the order are highly adapted for an aquatic existence at the water surface. All are web-footed for efficient swimming (although some have subsequently become mainly terrestrial).

Evolution

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The earliest known Anseriform is the recently discovered Vegavis, which lived during the Cretaceous period[1]. 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. T he extinct dromornithids represent early offshoots of the anseriform line, possibly derived from screamer-like ancestors[citation needed], 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.

All Anseriformes have this basic structure, but many have subsequently adopted alternative feeding strategies: geese graze on plants, the saw-billed ducks catch fish; even the screamers, which have bills that seem on first sight more like those of the game birds, still have vestigal lamellae. The prehistoric wading presbyornithids and the huge and possibly carnivorous dromornithids were even more bizarre.

Systematics

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The Anseriformes and the Galliformes (pheasants etc) are the most primitive neognathous birds, and should follow ratites and tinamous in bird classification systems.

Anatidae systematics, especially regarding placement of some "odd" genera in the dabbling ducks or shelducks, is not fully resolved. See the Anatidae article for more information, and for alternate taxonomic approaches.

ORDER ANSERIFORMES

Crested Screamer (Chauna torquata)
Magpie Goose (Anseranas semipalmata), sole survivng member of a Mesozoic lineage
Reconstruction of Dromornis stirtoni, a mihirung

The fossil Gastornithidae (diatrymas) are also occasionally included herein as a family.

Some fossil anseriform taxa not assignable with certainty to a family are:

In addition, a considerable number of mainly Late Cretaceous and Paleogene fossils have been described where it is uncertain whether or not they are anseriforms. This is because almost all orders of aquatic birds living today either originated or underwent a major radiation during that time, making it hard to decide whether some waterbird-like bone belongs into this family or is the product of parallel evolution in a different lineage due to adaptive pressures.

Photos

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Taxonomy

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The Order Anseriformes is further organized into finer groupings including:

Families

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Anatidae

Anatidae is the biological that includes the ducks, geese and swans. The family has a cosmopolitan distribution, occurring on all the world's continents except Antarctica and on most of the world's islands and island groups. These are birds that are evolutionarily adapted for swimming, floating on the water surface, and in some cases diving in at least shallow water. (The Magpie-goose is no longer considered to be part of the Anatidae, but is placed in its own family Anseranatidae.) The family contains around 146 species in 40 genera. They are generally herbivorous, and are monogamous breeders. A number of species undertake annual migrations. A few species have been domesticated for agriculture, and many others are hunted for food and recreation. Five species have become extinct since 1600, and many more are threatened with extinction. [more]

Anhimidae

The screamers are a small family of , the Anhimidae. For a long time they were thought to be related to the Galliformes because of similar bills, but they are truly related to ducks (family Anatidae), most closely to the Magpie-goose (which some DNA evidence suggests[citation needed] are closer to screamers than to ducks). [more]

Anseranatidae

The Magpie-goose, Anseranas semipalmata, is a species found in coastal northern Australia and savannah in southern New Guinea. It is a unique member of the order Anseriformes, and arranged in a family and genus distinct from all other living waterfowl. The Magpie-goose is a resident breeder in northern Australia and in southern New Guinea. [more]

Dendrocygnidae

Dendrocygninae is a of the duck, goose and swan family of birds, Anatidae. In other taxonomical approaches, they are either considered a separate family Dendrocygnidae, or a tribe Dendrocygnini in the goose subfamily Anserinae (e.g. Terres & NAS, 1991). [more]

At least 11 species and subspecies belong to the Family Dendrocygnidae.

More info about the Family Dendrocygnidae may be found here.

References

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Footnotes

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  1. ^ Clarke et al. (2005)

Sources

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Last Revised: September 22, 2009
2009/09/22 07:32:54