''Diogenornis'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

ratite Ratites () are a polyphyletic group consisting of all birds within the infraclass Palaeognathae that lack keels and cannot fly. They are mostly large, long-necked, and long-legged, the exception being the kiwi, which is also the only nocturnal ...

s, that lived from the Middle Paleocene to the

Early Eocene In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

(

Riochican The Riochican () age is a period of geologic time (57.0–54.0 Ma) within the Paleocene and Eocene epochs of the Paleogene, used more specifically within the South American land mammal ages (SALMA). It follows the Peligran and precedes the Itabora ...

Casamayoran The Casamayoran () age is a period of geologic time (50.0–48.0 Ma) within the Early Eocene epoch of the Paleogene, used more specifically within the South American land mammal age (SALMA) classification. It follows the Itaboraian and precedes th ...

in the SALMA classification).''Diogenornis''
at

Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

.org It was described in 1983 by Brazilian scientist Herculano Marcos Ferraz de Alvarenga based on fossils found in the

Itaboraí Formation The Itaboraí Formation () is a highly list of fossiliferous stratigraphic units in Brazil, fossiliferous geologic Formation (geology), formation and LagerstätteKellner & Campos, 1999, p.399 of the Itaboraí Basin in Rio de Janeiro (state), Rio d ...

in southeastern

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

.Alvarenga, H.M.F. (1983) Uma ave ratitae do Paleoceno Brasileiro: bacia calcária de Itaboraí, Estado do Rio de Janeiro, Brasil. ''Boletim do Museu Nacional, Nova Série, Geologia'' 41: 1–8 The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

is ''D. fragilis''. It grew to about two thirds the size of the modern

greater rhea The greater rhea (''Rhea americana'') is a species of flightless bird native to eastern South America. Other names for the greater rhea include the grey, common, or American rhea; ema (Portuguese (language), Portuguese); or ñandú (Guaraní lang ...

, at about of height.

Description

While initially considered a member of the family Opisthodactylidae, further examination of the fossil remains showed that it was more similar to the modern rhea. According to

Gerald Mayr Gerald Mayr is a German palaeontologist who is Curator of Ornithology at the Senckenberg Research Institute in Frankfurt am Main, Hesse. He has published extensively on fossil birds, especially the Paleogene avifauna of Europe.Mayr, Gerald (2016). ...

, ''Diogenornis'' is best considered a stem-group member of the

Rheidae Rheidae is a family of flightless ratite birds which first appeared in the Paleocene. It is today represented by the sole living genus '' Rhea'', but also contains several extinct genera. Taxonomy Order Rheiformes (Forbes, 1884) Furbringer, 188 ...

.Mayr, G. (2009). Paleogene fossil birds. Springer. However, recent phylogenetic studies have shown a closer affiliation to Australian ratites, the

cassowaries Cassowaries (; Biak language, Biak: ''man suar'' ; ; Papuan_languages, Papuan: ''kasu weri'' ) are flightless birds of the genus ''Casuarius'', in the order Casuariiformes. They are classified as ratites, flightless birds without a keel (bird a ...

and

emu The emu (; ''Dromaius novaehollandiae'') is a species of flightless bird endemism, endemic to Australia, where it is the Tallest extant birds, tallest native bird. It is the only extant taxon, extant member of the genus ''Dromaius'' and the ...

s. This may reevaluate the origins and distribution of this clade, expanding their range to the South American Paleocene, well before the appearance of '' Emuarius''.H. Alvarenga, Diogenornis fragilis Alvarenga, 1985, restudied: a South American ratite closely related to Casuariidae, 2010 Recent findings nonetheless show that it co-existed with early rheas, meaning the ratite diversity of South America was very high during the

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

.Agnolin et al, "Unexpected diversity of ratites (Aves, Palaeognathae) in the early Cenozoic of South America: palaeobiogeographical implications Article in Alcheringa" ''An Australasian Journal of Palaeontology'' July 2016 DOI: 10.1080/03115518.2016.1184898 ''Diogenornis'' possesses a rather narrow beak, similar to that of

tinamous Tinamous () are members of the order Tinamiformes (), and family Tinamidae (), divided into two distinct subfamily, subfamilies, containing 46 species found in Mexico, Central America, and South America. The word "tinamou" comes from the Carib la ...

, lithornithids and

, as well as rather large wings. These traits, both rather unspecialised, seem to suggest a then recent development from a flying ancestor.

References

Casuariiformes Ratites Prehistoric bird genera Eocene birds of South America Ypresian life Casamayoran Riochican Itaboraian Paleogene Brazil Fossils of Brazil Fossil taxa described in 1983 {{Casuariiformes-stub