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Finless sleeper ray
The finless sleeper ray (''Temera hardwickii'') is a species of electric ray in the family Narkidae, and the sole member of its genus. It is found over the continental shelf of Southeast Asia from the eastern Andaman Sea to Vietnam and Borneo. Typically growing no more than long, it may be the smallest cartilaginous fish. The finless sleeper ray is the only electric ray that lacks dorsal fins. It has an oval pectoral fin disc that varies from longer than wide to wider than long, depending on age, and a short, robust tail that terminates in a short, deep caudal fin. The trailing margins of its pelvic fins are sexually dimorphic, being more concave in males.
Like other members of its family, the finless sleeper ray can generate a defensive electric shock from paired electric organs in its disc. It gives birth to live young, with the developing embryos nourished by yolk. A litter size of four has been recorded from one individual. The International Union for Conservation of Nature (IUCN) has assessed the finless sleeper ray as Vulnerable. This slow-reproducing species is caught by intensive bottom trawl and possibly other fisheries throughout its range, which likely cause high mortality regardless of whether it is discarded or utilised.
==Taxonomy and phylogeny==
The finless sleeper ray was described as a new species and genus by English zoologist John Edward Gray in an 1831 issue of the scientific journal ''Zoological Miscellany''. His account was based on two specimens collected from Penang in Malaysia by General Thomas Hardwicke and presented to the British Museum. Hence, Gray named the ray ''Temera hardwickii'', or "Hardwicke's Temera". He noted that the new genus was most closely affiliated to the genus ''Narke'', because it has no dorsal fins while ''Narke'' has only one and other electric rays have two.〔 A 2012 phylogenetic study, based on morphology, corroborated the close relationship between ''Temera'' and ''Narke''.〔
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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