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Phorusrhacids, colloquially known as terror birds, are an extinct clade of large carnivorous flightless birds that were the largest species of apex predators in South America during the Cenozoic, 62–1.8 million years (Ma) ago. They were roughly tall. Their closest modern-day relatives are believed to be the 80 cm-tall seriemas. ''Titanis walleri'', one of the larger species, is known from Texas and Florida in North America. This makes the phorusrhacids the only known example of large South American predators migrating north during the Great American Interchange (which occurred after the volcanic Isthmus of Panama land bridge rose ca. 10-15 Ma).〔(Land Bridge Linking Americas Rose Earlier Than Thought, LiveScience.com )〕 It was once believed that ''T. walleri'' only became extinct around the time of the arrival of humans in North America, but subsequent datings of ''Titanis'' fossils have failed to provide evidence for their survival more recently than 1.8 Ma. However, there exist additional findings that date from 450,000 years ago〔 and 17,000 years ago,〔Herculano Alvarenga, Washington Jones, and Andrés Rinderknecht (2010). (The youngest record of phorusrhacid birds (Aves, Phorusrhacidae) from the late Pleistocene of Uruguay ). ''Neues Jahrbuch für Geologie and Paläont. Abh'', 256: 229–234; Stuttgart.〕 which suggest that at least some phorusrhacids survived until the late Pleistocene in Uruguay, although this has been considered as dubious.〔Agnolin, F. (2013). (La posición sistemática de ''Hermosiornis'' (Aves, Phororhacoidea) y sus implicancias filogenéticas ). ''Revista del Museo Argentino de Ciencias Naturales'' nueva serie, 15(1), 39-60.〕 Phorusrhacids may have even made their way into Africa, with the genus ''Lavocatavis'' recently discovered in Algeria, although its status as a true phorusrhacid is questionable.〔Mourer-Chauviré, C. ''et al.'' (2011) A Phororhacoid bird from the Eocene of Africa. ''Naturwissenschaften'' 〕 A possible European form, ''Eleutherornis'', has also been identified, suggesting that this group had a wider geographical range in the Paleogene.〔Delphine Angst ''et al.'' (2013) (A LARGE PHORUSRHACID BIRD FROM THE MIDDLE EOCENE OF FRANCE ).''〕 ==Description== Based on Claudia P. Tambussi, Ricardo de Mendoza, Federico J. Degrange, and Mariana B. Picasso’s work, the phorusrhacid's neck can be divided into three main regions (region 1, region 2, and region 3). In the higher regions of the neck, the phorusrhacid has bifurcate neural spines (BNS) while it has high neural spines in its lower regions. This suggests that the phorusrhacid had a highly flexible and developed neck allowing it to carry its heavy head and strike with terrifying speed and power. Although the phorusrhacid externally looks like it has a short neck, its flexible skeletal neck structure proves that it can expand farther beyond the expected reach and intimidate its prey using its height, allowing it to strike more easily. Once stretched out into its full length in preparation for a downward strike, its developed neck muscles and heavy head can produce enough momentum and power to cause fatal damage to the Terror Bird’s prey. ''Kelenken guillermoi'', from the Langhian stage of the Miocene epoch, some 15 million years ago, discovered in Patagonia in 2006, represents the largest bird skull yet found. The fossil has been described as being a , nearly intact skull. The beak is roughly long and curves in a hook shape that resembles an eagle's beak. Most species described as phorusrhacid birds were smaller, tall, but the new fossil belongs to a bird that probably stood about tall. Scientists theorize that the large terror birds were extremely nimble and quick runners able to reach speeds of . 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「Phorusrhacidae」の詳細全文を読む スポンサード リンク
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