''Presbyornis'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

anseriform Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which inc ...

bird. It contains two unequivocally accepted

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

; the well-known ''P. pervetus'' and the much lesser-known ''P. isoni''. ''P. pervetus'' was approximately the size and shape of a

goose A goose ( : geese) is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera ''Anser'' (the grey geese and white geese) and '' Branta'' (the black geese). Some other birds, mostly related to the ...

, 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.

Fossils

The fossil record of ''P. pervetus'' includes many complete skeletons from

Green River Formation The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. The sediments are deposited in very fine ...

sites (Early

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

), suggesting that the birds nested in colonies and possibly were liable to succumb to

botulism Botulism is a rare and potentially fatal illness caused by a toxin produced by the bacterium ''Clostridium botulinum''. The disease begins with weakness, blurred vision, feeling tired, and trouble speaking. This may then be followed by weakne ...

, similar to many colony-nesting

waterfowl Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which in ...

or shorebirds today. ''P. isoni'' is known from the Late

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...

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 ...

(

Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...

, 61-62 MYA) humerus ( USNM 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 The Bouldnor Formation is a geological formation in the Hampshire Basin of southern England. It is the youngest formation of the Solent Group and was deposited during the uppermost Eocene and lower Oligocene. Stratotype and occurrence The Bo ...

) 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 The University of Kansas Natural History Museum is part of the University of Kansas Biodiversity Institute, a KU designated research center dedicated to the study of the life of the planet. The museum's galleries are in Dyche Hall on the unive ...

10105) found in

Colton Formation The Colton Formation is a Formation (geology), geologic formation in Utah. Its age is based on its position between the Upper Cretaceous-Paleocene North Horn Formation and overlying Green River Formation. The name was first used by P.T. Walton i ...

sediments of the

Wasatch Plateau The Wasatch Plateau is a plateau located southeast of the southernmost part of the Wasatch Range in central Utah. It is a part of the Colorado Plateau. Geography The plateau has an elevation of and includes an area of . Its highest point in the ...

near

Ephraim, Utah Ephraim is a city in Sanpete County, Utah, United States. The population was 5,611 at the 2020 census, making it the largest city in Sanpete County. It is the location of Snow College and is located along U.S. Route 89. History The first settlem ...

. Undescribed fossils are also known from the Paleocene of

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

and possibly the Early Eocene of

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...

. The

coracoid A coracoid (from Greek κόραξ, ''koraks'', raven) is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is prese ...

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 Flamingos or flamingoes are a type of wading bird in the family Phoenicopteridae, which is the only extant family in the order Phoenicopteriformes. There are four flamingo species distributed throughout the Americas (including the Caribbea ...

, but it was reclassified as an anseriform when the

duck Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Divided among several subfamilies, they are a form ...

-like anatomy of its

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

and

bill Bill(s) may refer to: Common meanings * Banknote, paper cash (especially in the United States) * Bill (law), a proposed law put before a legislature * Invoice, commercial document issued by a seller to a buyer * Bill, a bird or animal's beak Plac ...

was found. Later, it was believed to represent a transitional stage between the anseriforms and the shorebirds, 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 A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

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 ducks.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