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The great hammerhead (''Sphyrna mokarran'') is the largest species of hammerhead shark, belonging to the family Sphyrnidae, attaining a maximum length of 6.1 m (20 ft). It is found in tropical and warm temperate waters worldwide, inhabiting coastal areas and the continental shelf. The great hammerhead can be distinguished from other hammerheads by the shape of its "hammer" (called the "cephalofoil"), which is wide with an almost straight front margin, and by its tall, sickle-shaped first dorsal fin. A solitary, strong-swimming apex predator, the great hammerhead feeds on a wide variety of prey ranging from crustaceans and cephalopods, to bony fishes, to smaller sharks. Observations of this species in the wild suggest that the cephalofoil functions to immobilize stingrays, a favored prey. This species has a viviparous mode of reproduction, bearing litters of up to 55 pups every two years. Although potentially dangerous, the great hammerhead rarely attacks humans. It sometimes behaves inquisitively toward divers and should be treated with respect. This shark is heavily fished for its large fins, which are extremely valuable on the Asian market as the main ingredient of shark fin soup. As a result, great hammerhead populations are declining substantially worldwide, and it has been assessed as Endangered by the International Union for Conservation of Nature (IUCN). ==Taxonomy and phylogeny== The great hammerhead was first described as ''Zygaena mokarran'' in 1837 by the German naturalist Eduard Rüppell. The name was later changed to the current ''Sphyrna mokarran''.〔 However, for many years the valid scientific name for the great hammerhead was thought to be ''Sphyrna tudes'', which was coined in 1822 by Achille Valenciennes. In 1950, Enrico Tortonese determined that the specimens illustrated by Valenciennes were in fact smalleye hammerheads, to which the name ''S. tudes'' then applied. As the next most senior synonym, ''Sphyrna mokarran'' became the great hammerhead's valid name. The lectotype for this species is a long male from the Red Sea.〔 }} }} }} }} }} Older studies based on morphology have generally placed the great hammerhead as one of the more derived members of its family, reflecting the traditional view that cephalofoil size gradually increased over the course of hammerhead shark evolution. However, this view has been refuted by phylogenetic analyses using nuclear and mitochondrial DNA, which found that the great hammerhead and the smooth hammerhead (''S. zygaena'') form a clade that is basal to all other ''Sphyrna'' species. These results also show that the first hammerheads to evolve had large rather than small cephalofoils. 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「Great hammerhead」の詳細全文を読む スポンサード リンク
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