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graceful shark
The graceful shark or Queensland shark (''Carcharhinus amblyrhynchoides'') is a species of requiem shark, in the family Carcharhinidae, found in the tropical Indo-Pacific, from the Gulf of Aden to northern Australia. It is a midwater species that has been recorded to a depth of . A stoutly built shark growing up to long, the graceful shark has a short, wedge-shaped snout, large, sickle-shaped pectoral fins and first dorsal fin, and black tips on most fins.
Graceful sharks prey mainly on bony fishes, and to a much lesser extent on cephalopods and crustaceans. It is viviparous, with females bearing litters of up to 9 pups following a 9– to 10-month gestation period. Off northern Australia, birthing occurs in January and February, with mating shortly after. This species is potentially dangerous, but has not been implicated in any attacks. It is caught incidentally by commercial fisheries throughout its range for meat, fins, and liver oil, though specific information is lacking. The International Union for Conservation of Nature has listed it under Near Threatened.
==Taxonomy and phylogeny==
Australian ichthyologist Gilbert Percy Whitley originally described the graceful shark as ''Gillisqualus amblyrhynchoides'', in a 1934 issue of ''Memoirs of the Queensland Museum''. He based his account on a 60-cm-long immature female caught off Cape Bowling Green in Queensland, hence the alternate common name Queensland shark.〔 Later authors have synonymized ''Gillisqualus'' with ''Carcharhinus''.〔
As with most ''Carcharhinus'' species, the evolutionary relationships of the graceful shark are poorly resolved. Based on morphology, Jack Garrick concluded in 1982 that its closest relative was the blacktip shark (''C. limbatus''), and that the two were closely related to the spinner shark (''C. brevipinna'').〔 Leonard Compagno, in his 1988 phenetic study, also grouped those species together, along with the smoothtooth blacktip shark (''C. leiodon'') and the finetooth shark (''C. isodon'').〔 However, molecular phylogenetic techniques have since found this interpretation to be invalid for the spinner, blacktip, and finetooth sharks.〔
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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