| Geranoididae | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Infraclass: | Palaeognathae |
| Family: | †Geranoididae Wetmore, 1933 |
| Genera | |
Geranoididae is a clade of extinct birds from the early to lateEocene and possibly earlyOligocene ofNorth America andEurope. These were mid-sized, long-leggedflightless birds.[1][2][3][4][5] Recent research shows that these birds may actually bepalaeognaths related to ostriches.[6]
It is rather unambiguous that geranoidids are either part of or stem representatives ofGruoidea, the clade that includes moderncranes,limpkins andtrumpeters, though their precise relationship varies among studies, some recovering them as sister taxa to another clade of flightless ratite-like birds, theeogruiids. The most recent consensus appears to be that geranoidids are outside of Gruoidea, with eogruiids being more closely related to modern cranes.[4] However,Mayr (2019) argued that close affinities between Geranoididae and thepalaeognathous family Palaeotididae are at least as well supported as the classification of geranoidids into the Gruiformes.[6]
The exact number of genera and species are also somewhat controversial. For instance, a recent study recoversGeranoides as possibly synonymous withPalaeophasianus andEogeranoides as possibly synonymous withParagrus.[4]
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 modernratites. Most if not all of them were forest dwellers, a lifestyle also present in contemporaneous ratites such asPalaeotis andRemiornis.[7] While competition and lack thereof between ratites and eogruiids has been examined extensively,[8][9][10] 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.[5][11]
Geranoidids are most common in Eocene fossil sites in North America, particularly in theWillwood Formation where up to six species are known.Galligeranoides occurs in the Eocene ofFrance in association with another flightless bird,Gastornis, potentially indicating that geranoidids took advantage of land bridges to arrive to Europe.[3] However, Mayr (2019) consideredGalligeranoides to be a member of Palaeognathae closely related toPalaeotis, and formally transferredGalligeranoides from the family Geranoididae to the family Palaeotididae. This transfer restricts the fossil record of the family Geranoididae to North America.[6]
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