''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 Swans are birds of the family (biology), family Anatidae within the genus ''Cygnus''. The swans' closest relatives include the goose, geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form t ...

-sized. Other fossils, more doubtfully assigned to this genus, are also known.

Fossils

The fossil record of ''P. pervetus'' includes many complete skeletons from Green River Formation sites (Early Eocene), suggesting that the birds nested in colonies and possibly were liable to succumb to botulism, similar to many colony-nesting waterfowl or

shorebirds 245px, A flock of Dunlins and Red knots">Red_knot.html" ;"title="Dunlins and Red knot">Dunlins and Red knots Waders or shorebirds are birds of the order Charadriiformes commonly found wikt:wade#Etymology 1, wading along shorelines and mudflat ...

today. ''P. isoni'' is known from the Late Paleocene

Aquia Formation The Aquia Formation is a geologic sandstone formation that extends from the upper Chesapeake Bay to the James River near Hopewell, Virginia. It consists of clayey, silty, very shelly, glauconitic sand. Fossil records indicate that this strat ...

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) humerus (

USNM The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. In 2021, with 7. ...

294116) and a fingerbone (USNM 294117) that were initially described, as well as from the humeri that were initially believed to be from '' Headonornis'' ( BMNH PAL 3686, 5105, 6240). As these are Late Eocene or even Early

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

(BMNH PAL 5105, Bembridge Marls) in age, they possibly belong to a distinct taxon. ''P. recurvirostris'' is a disputed species possibly synonymous with ''P. pervetus''; it is known from a partial wing ( KUVP 10105) found in Colton Formation Eocene sediments of the Wasatch Plateau near Ephraim, Utah. Undescribed fossils are also known from the Paleocene of Utah and possibly the Early Eocene of Mongolia. The coracoid still assigned to ''Headonornis'' may also belong into this genus.

Description

''Presbyornis'' was one of the first anseriforms. Because of its long legs and neck, ''Presbyornis'' was initially mistaken for a flamingo, but it was reclassified as an anseriform when the duck-like anatomy of its skull and bill was found. Later, it was believed to represent a transitional stage between the anseriforms and the

, but it is now considered a member of an extinct group of anseriforms which was most closely related to modern screamers. Judging from numerous fossil findings, ''Presbyornis'' is presumed to have lived in colonies around shallow lakes. Its broad, flat bill was used to filter food (small plants and animals) from the water, in the manner of today's

dabbling duck The Anatinae are a subfamily of the family Anatidae ( swans, geese and ducks). Its surviving members are the dabbling ducks, which feed mainly at the surface rather than by diving. The other members of the Anatinae are the extinct moa-nalo, a yo ...

s.Palmer (1999)

Footnotes

References

* (2001): The Fossil Waterfowl (Aves: Anseriformes) from the Eocene of England. ''American Museum Novitates'' 3354: 1-15
PDF fulltext
* (2002): A New Presbyornithid Bird (Aves, Anseriformes) from the Late Cretaceous of Southern Mongolia. ''American Museum Novitates'' 3386: 1-11
PDF fulltext
* * (1926): Fossil birds from the Green River Deposits of Eastern Utah. ''Annals of the Carnegie Museum'' 16: 391–402.

External links

Reconstruction of ''Presbyornis'' at critters.pixel-shack.com
{{Taxonbar, from=Q134586 Bird genera Paleocene birds Eocene birds Oligocene birds Paleogene birds of North America Fossil taxa described in 1926 Taxa named by Alexander Wetmore