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| regnum = Animalia | phylum = Chordata | classis = Actinopterygii | superordo = Osteoglossomorpha | ordo = Ichthyodectiformes | familia = Ichthyodectidae | subfamilia = Ichthyodectinae | genus = ''Xiphactinus'' | genus_authority = Leidy, 1870 | subdivision_ranks = Species | subdivision = *''Xiphactinus audax'' *''Xiphactinus vetus'' }} ''Xiphactinus'' (from Latin and Greek for "sword-ray") is an extinct genus of large (4.5 to 6 m (15 to 20 feet) long) predatory marine bony fish that lived during the Late Cretaceous. When alive, the fish would have resembled a gargantuan, fanged tarpon (to which it was, however, not related).〔("Xiphactinus audax Leidy" )〕 The species ''Portheus molossus'' described by Cope〔 is a junior synonym of ''X. audax''. Skeletal remains of ''Xiphactinus'' have come from Kansas (where the first ''Xiphactinus'' fossil was discovered during the 1850s), Alabama and Georgia in the United States as well as Europe, Australia, Canada and Venezuela.〔Carrillo-Briceño, J., Alvarado-Ortega, J. & Torres, C. (2012). (Primer registro de ''Xiphactinus'' Leidy, 1870, (Teleostei: Ichthyodectiformes) en el Cretácico Superior de América del Sur (Formación La Luna, Venezuela) ). ''Revista Brasilera de Paleontología'' 15(3):327-335〕 ==Palaeobiology== Species of ''Xiphactinus'' were voracious predatory fish. At least a dozen specimens of ''X. audax'' have been collected with the remains of large, undigested or partially digested prey in their stomachs. In particular, one fossil specimen was collected by George F. Sternberg with another, nearly perfectly preserved long ichthyodectid ''Gillicus arcuatus'' inside of it. The larger fish apparently died soon after eating its prey, most likely owing to the smaller fish prey's struggling and rupturing an organ as it was being swallowed. This fossil can be seen at the Sternberg Museum of Natural History in Hays, Kansas.〔〔("''Xiphactinus Audax''" ) (JPG). Sternberg Museum of Natural History. (archived: oceansofkansas.com).〕 Like many other species in the Late Cretaceous oceans, a dead or injured individual was likely to be scavenged by sharks (''Cretoxyrhina'' and ''Squalicorax''). The remains of a ''Xiphactinus'' were found within a large specimen of ''Cretoxyrhina'' collected by Charles H. Sternberg. The specimen is on display at the University of Kansas Museum of Natural History. Virtually nothing is known about the larval or juvenile stages. The smallest fossil specimen of ''X. audax'' consists of a tooth bearing premaxilla and lower jaws of an individual estimated to be about long.〔〔("''Xiphactinus Audax''" ) (JPG). oceansofkansas.com.〕 The species and all other ichthyodectids went extinct near the end of the Late Cretaceous – see Cretaceous–Paleogene extinction event. An incomplete skull of what may be a new species of ''Xiphactinus'' was found in 2002 in the Czech Republic, in a small town called Sachov next to Borohradek city, by student Michal Matejka. In July 2010 the bones of a ''Xiphactinus'' were discovered near Morden, Manitoba, Canada. The specimen is about six metres long and was found with the flipper of a mosasaur between its jaws.〔("Major Fossil Discovery Underway in Morden" ) (PDF). Canadian Fossil Discovery Centre. July 16, 2010. Press release.〕 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「Xiphactinus」の詳細全文を読む スポンサード リンク
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