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Pincushion ray
The pincushion ray or thorny freshwater stingray (''Dasyatis ukpam'') is a little-known species of stingray in the family Dasyatidae, found in the rivers and lakes of West Africa. A heavy-bodied ray measuring up to across, this species can be distinguished by its rounded pectoral fin disk, reduced or absent stinging tail spine, and—in adults—numerous stout thorns covering its back and tail. In lieu of a long tail spine as in other stingrays, the pincushion ray employs these thorny denticles in defense. Seldom encountered since it was originally described, this species has been assessed as Endangered by the International Union for Conservation of Nature (IUCN).
==Taxonomy==
John Alexander Smith scientifically described the pincushion ray in 1863, in ''Proceedings of the Royal Physical Society of Edinburgh''. He named it ''ukpam'', as that is the local indigenous name for freshwater stingrays. Because he saw the single, reduced tail spine of this ray as an intermediate condition between ''Urogymnus'', which is spineless, and ''Trygon'' (=''Dasyatis''), which has one or more spines, Smith coined the genus ''Hemitrygon'' (from the Greek ''hemi'' meaning "half") for this species. Subsequent authors have regarded it as either a member of ''Dasyatis'' or ''Urogymnus''.〔
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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