Eogruids

Eogruidae (also spelled Eogruiidae in some publications) is a family of large, flightless birds that inhabited Asia from the Eocene to Pliocene, it was formerly thought to be related to cranes, limpkins and trumpeters and that the similarities with ostriches were due to similar speciations to cursoriality, with both groups showing reduced numbers of toes to two in some taxa.Kurochkin, E.N. 1976. A survey of the Paleogene birds of Asia. Smithsonian Contributions to Paleobiology 27:75-86.Kurochkin, E.N. 1981. New representatives and evolution of two archaic gruiform families in Eurasia. Transactions of the Soviet-Mongolian Paleontologial Expedition 15:59-85. It has been suggested that competition from true ostriches has caused the extinction of these birds, though this has never been formally tested and several ostrich taxa do occur in the late Cenozoic of AsiaMayr, G. (2009). Paleogene fossil birds. Springer. and some species do occur in areas where ostrich fossils have also been found. It has been suggested that the family is paraphyetic, with Ergilornithidae more closely related to modern ostriches than to '' Eogrus'' or '' Sonogrus''.

Description

Most eogruids are known from rather sparse remains, mostly the tarso-metatarsals and toes. The former are generally slender with a distinct crest along the lateral side of the plantar surface. The trochlea for the second toe shows a progressive reduction along the various taxa, culminating in its utter absence in ''Amphipelargus''.

Other skeletal remains are rare. Wing elements are known in a few taxa; these are generally highly reduced, suggesting that these birds were flightless. The exception appears to be ''Eogrus'' itself, which does not show much phalange reduction and hypothetically could still fly, though the rest of the postcranial skeleton is already specialised for cursoriality.

Classification

Eogruids were formerly considered to be Gruiformes within the crane-limpkin-trumpeter line, Gruoidea, the exception being Olson 1985 which declared them to be stem-ostriches. A study in 2021 based on newly described remains found that eogruids and the related Ergilornithidae are indeed members of Struthoniformes.Mayr, G. & Zelenkov, N. (2021) Extinct crane-like birds (Eogruidae and Ergilornithidae) from the Cenozoic of Central Asia are indeed ostrich precursors. ''Ornithology'', https://doi.org/10.1093/ornithology/ukab048

More derived taxa such as ''Ergilornis'' and ''Amphipelargus'' were sometimes classified as a separate family, Ergilornithidae, but they are now generally accepted to be a subfamily within Eogruidae. Eogruids are rather similar to Geranoididae, a clade of similar flightless gruiforms from North America and Europe, and both groups have occasionally been classified as sister taxa. Recently geranoidids have been recovered as basal to the rest of Gruoidea, however, while eogruids are sister-taxa to cranes.

Taxonomy

There is some contention in regards to ergilornithine genera, particularly ''Amphipelargus'' and ''Urmiornis'', which have assimilated each other's species from study to study. The most recent consensus is that nearly all Neogene eogruid remains belong to ''Urmiornis'', while a few western Eurasian taxa can be referred to as ''Amphipelargus''.

*†'' Eogrus''
**†''Eogrus aeola''
**†''Eogrus crudus''
**†''Eogrus turanicus''
*†'' Sonogrus''
**†''Sonogrus gregalis''
*†'' Proergilornis''
*†Ergilornithinae
**†'' Ergilornis''
***†''Ergilornis rapidus''
***†''Ergilornis minor'' (Synonym/s - "Proergilornis")
**†'' Amphipelargus''
***†''Amphipelargus majori''
***†''Amphipelargus cracrafti''
***†An unnamed species possibly within this genus.
**†'' Urmiornis''
***†''Urmiornis brodkorbi''
***†''Urmiornis dzabghanensis''
***†''Urmiornis maraghanus''
***†''Urmiornis orientalis''
***†''Urmiornis ukrainus''

References

{{Taxonbar, from=Q3726691

Ratites
Prehistoric birds of Asia
Extinct flightless birds
Prehistoric bird families