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Gastornis
''Gastornis'' is an extinct genus of large flightless birds that lived during the late Paleocene and Eocene epochs of the Cenozoic era. The genus is currently thought to contain three or four distinct species, known from incomplete fossil remains, found in western-central Europe (England, Belgium, France and Germany). More complete specimens are known from a fourth, North American species, which had previously been classified in the distinct genus ''Diatryma''. Many scientists now consider ''Diatryma'' to be so similar to the other species of ''Gastornis'' that it should also be included in that genus. A fifth species, also previously classified in its own genus, is known from China.
''Gastornis'' species were very large birds, and have traditionally been considered to be predators of small mammals. However, several lines of evidence, including the lack of hooked claws in known ''Gastornis'' footprints and studies of their beak structure have caused scientists to reinterpret these birds as herbivores that probably fed on tough plant material and seeds.
==Description==
''Gastornis'' is known from a large amount of fossil remains, but the clearest picture of the bird comes from a few nearly complete specimens of the species ''G. gigantea''. These were generally very large birds, with huge beaks and massive skulls superficially similar to the carnivorous South American "terror birds" (phorusrhacids). The largest known species, ''G. gigantea'' could grow to the size of the largest moas, and reached about in maximum height.〔
The skull of ''G. gigantea'' was huge compared to the body and powerfully built. The beak was extremely tall and compressed (flattened from side to side). Unlike other species of ''Gastornis'', ''G. gigantea'' lacked characteristic grooves and pits on the underlying bone. The 'lip' of the beak was straight, without a raptorial hook as found in the predatory phorusrhacids. The nostrils were small and positioned close to the front of the eyes about midway up the skull. The vertebrae were short and massive, even in the neck. The neck was relatively short, consisting of at least 13 massive vertebrae. The torso was relatively short. The wings were vestigial, with the upper wings bones small and highly reduced, similar in proportion to the wings of the cassowary.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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