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Teratorns (from the Greek Τερατορνις ''Teratornis'', 'monster bird') are an extinct group of very large birds of prey that lived in North and South America from the Miocene to Pleistocene epochs. They include some of the largest known flying birds. ==Taxonomy== Teratornithidae are related to New World vultures (''Cathartidae'', syn. ''Vulturidae'').〔 So far, at least five species in four genera have been identified: *''Teratornis merriami''.〔 This is by far the best-known species. Over a hundred specimens have been found, mostly from La Brea Tar Pits. It stood about 75 cm (29.5 in) tall with estimated wingspan of perhaps 3.5 to 3.8 metres (11.5 to 12.5 ft), and weighed about 15 kg (33 lb); making it about a third bigger than extant condors. It became extinct at the end of Pleistocene, some 10,000 years ago. *''Teratornis woodburnensis''.〔 The first species to be found north of the La Brea Tar Pits, this partial specimen was discovered at Legion Park, Woodburn, Oregon. It is known from a humerus, parts of the cranium, beak, sternum, and vertebrae which indicate an estimated wingspan of over 4 meters (14 ft). The find dates to the late Pleistocene, between 11,000 and 12,000 years ago, in a strata which is filled with the bones of Mastodon, Sloth and Condors, and bears evidence of human habitation. *''Aiolornis incredibilis'',〔 previously known as ''Teratornis incredibilis''. This species is fairly poorly known; finds from Nevada and California include several wing bones and part of the beak. They show remarkable similarity with ''merriami'' but are uniformly about 40% larger: this would translate to a mass of up to 23 kg (50 lb) and a wingspan of about 5.5 metres (18.04 ft) for ''incredibilis''. The finds are dated from the Pliocene to the late Pleistocene, which is a considerable chronological spread, and thus it is uncertain whether they actually represent the same species. *''Cathartornis gracilis''.〔 This species is known only from a couple of leg bones found from La Brea Ranch. Compared to ''T. merriami'', remains are slightly shorter and clearly more slender, indicating more gracile build. *''Argentavis magnificens''.〔 A partial skeleton of this enormous teratorn was found from La Pampa, Argentina. It is the largest flying bird known to have existed. It is the oldest known teratorn, dating to late Miocene, about 6 to 8 million years ago, and one of the very few teratorn finds in South America. Initial discovery included portions of the skull, incomplete humerus and several other wing bones. Even conservative estimates put its wingspan at 6 meters and up (some 20 ft), and it may have been as much as 8 metres (26 ft). The weight of the bird was estimated to have been around 80 kg (176 lb). * Another form, ''"Teratornis" olsoni'', was described from the Pleistocene of Cuba, but its affinities are not completely resolved; it might not be a teratorn at all, but has also been placed in its own genus, ''Oscaravis''. There are also undescribed fossils from southwestern Ecuador, but apart from these forms, teratorns were restricted to North America.〔 Some cryptozoologists such as Ken Gerhard, and Mark A. Hall have expressed interest in Teratorns as a possible explanation of anecdotal sightings of very large birds in Texas and Illinois and popularly known as Thunderbirds. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Teratornithidae」の詳細全文を読む スポンサード リンク
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