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winghead shark
The winghead shark (''Eusphyra blochii'') is a species of hammerhead shark, and part of the family Sphyrnidae. Reaching a length of , this small brown to gray shark has a slender body with a tall, sickle-shaped first dorsal fin. Its name comes from its exceptionally large "hammer", or cephalofoil, which can be as wide as half of the shark's total length. The function of this structure is unclear but may relate to the shark's senses. The wide spacing of its eyes grants superb binocular vision, while the extremely long nostrils on the leading margin of the cephalofoil may allow for better detection and tracking of odor trails in the water. The cephalofoil also provides a large surface area for its ampullae of Lorenzini and lateral line, with potential benefits for electroreception and mechanoreception respectively.
Inhabiting the shallow coastal waters of the western Indo-Pacific, the winghead shark feeds on small bony fishes, crustaceans, and cephalopods. It gives birth to live young, with the developing embryos receiving nourishment through a placental connection. Females produce annual litters of 6–25 pups; depending on region, birthing may occur from February to June after a gestation period of 8–11 months. This harmless species is widely fished for meat, fins, liver oil, and fishmeal. The International Union for Conservation of Nature (IUCN) has assessed it as Near Threatened, as it is thought to have declined in some parts of its range due to over-exploitation.
==Taxonomy==
In 1785, German naturalist Marcus Elieser Bloch described a shark that he referred to ''Squalus zygaena'' (a synonym of ''Sphyrna zygaena'', the smooth hammerhead). French zoologist Georges Cuvier, as a brief footnote to the account of ''S. zygaena'' in his 1817 ''Le Règne animal distribué d'après son organisation, pour servir de base à l'histoire naturelle des animaux et d'introduction à l'anatomie comparée'', observed that Bloch's specimen (which he labeled "''z. nob. Blochii''") was not a smooth hammerhead but rather a different species. Although Cuvier did not propose a proper binomial name, his colleague Achille Valenciennes interpreted it as such in 1822 when he described another specimen of the same species in detail, calling it ''Zygaena Blochii nobis'' and attributing the name to Cuvier.〔〔
In 1862, Theodore Gill placed the winghead shark in its own genus ''Eusphyra'', derived from the Greek ''eu'' ("good") and ''sphyra'' ("hammer").〔〔 However, subsequent authors did not accept ''Eusphyra'' and preferred to keep this species with the other hammerheads in the genus ''Sphyrna''. ''Eusphyra'' was resurrected by Henry Bigelow and William Schroeder in 1948, and came into wider usage after additional taxonomic research was published by Leonard Compagno in 1979 and 1988. Nevertheless, some sources still refer to this species as ''Sphyrna blochii''.〔〔 Other common names for the winghead shark include arrowhead, arrow headed hammerhead shark, and slender hammerhead.〔
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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