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

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' ...

and possibly 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 ...

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

and

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

. These were mid-sized, long-legged

flightless birds Flightless birds are birds that through evolution lost the ability to fly. There are over 60 extant species, including the well known ratites (ostriches, emu, cassowaries, rheas, and kiwi) and penguins. The smallest flightless bird is the ...

.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 The trumpet is a brass instrument commonly used in classical and jazz ensembles. The trumpet group ranges from the piccolo trumpet—with the highest register in the brass family—to the bass trumpet, pitched one octave below the standard ...

, though their precise relationship varies among studies, some recovering them as sister taxa to another clade of flightless ratite-like birds, the

eogruiids Eogruidae (also spelled Eogruiidae in some publications) is a family of large, flightless birds that inhabited Asia from the Eocene to Pliocene epochs. Related to modern ostriches, it was formerly thought to be related to cranes, limpkins and tr ...

. 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 * Georg Mayr (1564–1623), Bavarian Jesuit pri ...

(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 ''Palaeophasianus'' is an extinct genus of flightless Geranoididae birds that lived in North America during the Eocene period. Robert Wilson Shufeldt classified ''Palaeophasianus'' as a galliform when he described it in 1913. However it was trans ...

'' 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 A ratite () is any of a diverse group of flightless, large, long-necked, and long-legged birds of the infraclass Palaeognathae. Kiwi, the exception, are much smaller and shorter-legged and are the only nocturnal extant ratites. The systematics o ...

. 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 extinct ...

'' and ''

Remiornis ''Remiornis heberti'' is an extinct species of paleognath bird from the Paleocene of France. It is a species comparable in size to modern rheas, and possibly related to another European Paleogene ratite, ''Palaeotis ''Palaeotis'' is a genus o ...

''. 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 The Willwood Formation is a sedimentary sequence deposited during the late Paleocene to early Eocene, or Clarkforkian, Wasatchian and Bridgerian in the North American land mammal age, NALMA classification.Galligeranoides'' occurs in the Eocene of

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

in association with another flightless bird, ''

Gastornis ''Gastornis'' is an extinct genus of large flightless birds that lived during the mid Paleocene to mid Eocene epochs of the Paleogene period. Fossils have been found in Europe, Asia and North America, with the remains from North America origina ...

'', 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