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The bowmouth guitarfish (''Rhina ancylostoma''), also called the shark ray or mud skate, is a species of ray and the sole member of the family Rhinidae. Its evolutionary affinities are not fully resolved, though it may be related to true guitarfishes and skates. This rare species occurs widely in the tropical coastal waters of the western Indo-Pacific, at depths of up to . Highly distinctive in appearance, the bowmouth guitarfish has a wide and thick body with a rounded snout and large shark-like dorsal and tail fins. Its mouth forms a W-shaped undulating line, and there are multiple thorny ridges over its head and back. It has a dorsal color pattern of many white spots over a bluish gray to brown background, with a pair of prominent black markings over the pectoral fins. This large species can reach a length of and weight of . Usually found near the sea floor, the bowmouth guitarfish prefers sandy or muddy areas near underwater structures. It is a strong-swimming predator of bony fishes, crustaceans, and molluscs. This species gives live birth to litters of two to eleven pups, which are nourished during gestation by yolk. The International Union for Conservation of Nature (IUCN) has assessed the bowmouth guitarfish as Vulnerable because it is widely caught by artisanal and commercial fisheries for its valuable fins and meat. It is viewed as a nuisance by trawlers, however, because its bulk and thorny skin cause it to damage netted catches. Habitat degradation and destruction pose an additional, significant challenge to this ray's survival. The bowmouth guitarfish adapts well to captivity and is displayed in public aquariums. ==Taxonomy and phylogeny== German naturalists Marcus Elieser Bloch and Johann Gottlob Schneider described the bowmouth guitarfish in their 1801 ''Systema Ichthyologiae''. Their account was based on a long specimen, now lost, collected off the Coromandel Coast of India. The genus name ''Rhina'' comes from the Greek ''rhinos'' ("snout"); the specific epithet ''ancylostoma'' is derived from the Greek ''ankylos'' ("curved" or "crooked") and ''stoma'' ("mouth").〔〔 Although Block and Schneider wrote the epithet as ''ancylostomus'' and that form appears in some literature, most modern sources regard the correct form to be ''ancylostoma''.〔 Other common names for this species include shark ray, mud skate, shortnose mud skate, bow-mouthed angel fish, and bow-mouthed angel shark.〔 The evolutionary relationships between the bowmouth guitarfish and other rays are debated. Morphological evidence generally points to a close relationship between ''Rhina'' and ''Rhynchobatus'', which are a group of rays known as the wedgefishes that also have large, shark-like fins. Morphological analyses have tended to place these two genera basally among rays, though some have them as basal to just the guitarfishes (Rhinobatidae) and skates (Rajidae) while others have them basal to all other rays except sawfishes (Pristidae).〔〔〔 A 2012 study based on mitochondrial DNA upheld ''Rhina'' and ''Rhynchobatus'' as sister taxa related to the guitarfishes, but also unexpectedly found that they formed a clade with the sawfishes rather than the skates.〔 In terms of classification, Bloch and Schneider originally placed the bowmouth guitarfish in the order Abdominales, a now-obsolete grouping of fishes defined by the positioning of their pelvic fins directly behind the pectoral fins.〔 Modern sources have included it variously in the order Rajiformes, Rhinobatiformes, Rhiniformes, or the newly proposed Rhinopristiformes.〔〔 The placement of the bowmouth guitarfish in the family Rhinidae originates from the group "Rhinae", consisting of ''Rhina'' and ''Rhynchobatus'', in Johannes Müller and Jakob Henle's 1841 ''Systematische Beschreibung der Plagiostomen''.〔 Later authors have also assigned this species to the family Rhinobatidae or Rhynchobatidae.〔〔 Joseph Nelson, in the 2006 fourth edition of ''Fishes of the World'', placed this species as the sole member of Rhinidae in the order Rajiformes, which is supported by morphological but not molecular data.〔〔 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「bowmouth guitarfish」の詳細全文を読む スポンサード リンク
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