Geranoididae is a clade of extinct birds from the early to late

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

and possibly early

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

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and

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

. These were mid-sized, long-legged

flightless birds Flightless birds are birds that cannot Bird flight, fly, as they have, through evolution, lost the ability to. There are over 60 extant species, including the well-known ratites (ostriches, emus, cassowary, cassowaries, Rhea (bird), rheas, an ...

.Gerald Mayr (2009). Paleogene Fossil Birds Recent research shows that these birds may actually be palaeognaths related to ostriches.

Classification

It is rather unambiguous that geranoidids are either part of or stem representatives of Gruoidea, the clade that includes modern cranes, limpkins and trumpeters, though their precise relationship varies among studies, some recovering them as sister taxa to another clade of flightless ratite-like birds, the eogruiids. The most recent consensus appears to be that geranoidids are outside of Gruoidea, with eogruiids being more closely related to modern cranes. However,

Mayr Mayr is a German surname. Notable people with the surname include: * Andrea Mayr (born 1979), Austrian female long-distance runner * Ernst Mayr (1904–2005), German American evolutionary biologist * Franz Xaver Mayr (1875–1965), Austrian gastro ...

(2019) argued that close affinities between Geranoididae and the palaeognathous family Palaeotididae are at least as well supported as the classification of geranoidids into the Gruiformes.

Taxonomy

The exact number of genera and species are also somewhat controversial. For instance, a recent study recovers '' Geranoides'' as possibly synonymous with '' Palaeophasianus'' and '' Eogeranoides'' as possibly synonymous with '' Paragrus''.

Paleobiology

Most geranoidids appear to have been flightless, with long legs and short wings, and presumably with herbivorous habits, giving them a profile and lifestyle similar to that of modern

ratites Ratites () are a polyphyletic group consisting of all birds within the infraclass Palaeognathae that lack keel (bird anatomy), keels and flightless bird, cannot fly. They are mostly large, long-necked, and long-legged, the exception being the Kiw ...

. Most if not all of them were forest dwellers, a lifestyle also present in contemporaneous ratites such as ''

Palaeotis ''Palaeotis'' is a genus of paleognath birds from the middle Eocene epoch of central Europe. One species is known, ''Palaeotis weigelti''. The holotype specimen is a fossil tarsometatarsus and phalanx. Lambrect (1928) described it as an extin ...

'' and '' Remiornis''. While competition and lack thereof between ratites and eogruiids has been examined extensively, niche partitioning between geranoidids and ratites has currently not, in spite of factors like geranoidids being most common in North America, where there are no ratites, or the fact that some European ratites were carnivorous.

Paleoecology and distribution

Geranoidids are most common in Eocene fossil sites in North America, particularly in the Willwood Formation where up to six species are known. '' Galligeranoides'' occurs in the Eocene of

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in association with another flightless bird, '' Gastornis'', potentially indicating that geranoidids took advantage of land bridges to arrive to Europe. However, Mayr (2019) considered ''Galligeranoides'' to be a member of Palaeognathae closely related to ''

'', and formally transferred ''Galligeranoides'' from the family Geranoididae to the family Palaeotididae. This transfer restricts the fossil record of the family Geranoididae to North America.

References

{{Taxonbar, from=Q3760888 Prehistoric bird families Extinct flightless birds Prehistoric birds of North America Struthioniformes Paleogene birds of North America Prehistoric birds of Europe