Anseriformes

Anseriformes
Temporal range:
Late Cretaceous-Holocene, 66–0Ma
Magpie goose, Anseranas semipalmata
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Superorder: Galloanserae
Order: Anseriformes
Wagler, 1831
Subgroups
Range of the waterfowl and allies
Synonyms

Anserimorphae

Anseriformes is an order of birds. It comprises about 150 living species in three families: Anhimidae (the screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, 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

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. The extinct dromornithids represent early offshoots of the anseriform line,[2] 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

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. Some unusual fossil groups, such as the Gastornithidae and Dromornithidae, are often found to be at the base of the Anseriformes family tree, or at least their closest relatives.[3][4]

Anatidae is traditionally divided into subfamilies Anatinae and Anserinae.[5] The Anatinae consists of tribes Anatini, Aythyini, Mergini and Tadornini.

The higher-order classification below follows a phylogenetic analysis performed by Angolin, 2007.[3]

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.

Molecular studies

Studies of the mitochnodrial DNA suggest the existence of four branches - Anseranatidae, Dendrocygninae, Anserinae and Anatinae - with Dendrocygninae being a subfamily within the family Anatidae and Anseranatidae representing an independent family.[6] The clade Somaterini has a single genus Somateria.

See also

References

  1. ↑ Clarke et al. (2005)
  2. ↑ Murray, P. F. & Vickers-Rich, P. (2004)
  3. ↑ 3.0 3.1 Angolin, F. (2007)
  4. ↑ Livezey, B. C. & Zusi, R. L. (2007)
  5. ↑ Gonzalez J, Düttmann H, Wink M (2009) Phylogenetic relationships based on two mitochondrial genes and hybridization patterns in Anatidae. J Zoolog 279: 310–318. doi: 10.1111/j.1469-7998.2009.00622.x
  6. ↑ Liu G, Zhou L, Zhang L, Luo Z, Xu W (2013) The complete mitochondrial genome of bean goose (Anser fabalis) and implications for anseriformes taxonomy. PLoS One 8(5):e63334. doi: 10.1371/journal.pone.0063334

See also

Wikimedia Commons has media related to Anseriformes.
The Wikibook Dichotomous Key has a page on the topic of: Anseriformes