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The plain maskray or brown stingray (''Neotrygon annotata'') is a species of stingray in the family Dasyatidae. It is found in shallow, soft-bottomed habitats off northern Australia. Reaching in width, this species has a diamond-shaped, grayish green pectoral fin disc. Its short, whip-like tail has alternating black and white bands and fin folds above and below. There are short rows of thorns on the back and the base of the tail, but otherwise the skin is smooth. While this species possesses the dark mask-like pattern across its eyes common to its genus, it is not ornately patterned like other maskrays. Benthic in nature, the plain maskray feeds mainly on caridean shrimp and polychaete worms, and to a lesser extent on small bony fishes. It is viviparous, with females producing litters of one or two young that are nourished during gestation via histotroph ("uterine milk"). This species lacks economic value but is caught incidentally in bottom trawls, which it is thought to be less able to withstand than other maskrays due to its gracile build. As it also has a limited distribution and low fecundity, the International Union for Conservation of Nature (IUCN) has listed it as Near Threatened. ==Taxonomy and phylogeny== The first scientific description of the plain maskray was authored by Commonwealth Scientific and Industrial Research Organisation (CSIRO) researcher Peter Last in a 1987 issue of ''Memoirs of the National Museum of Victoria''. The specific name ''annotatus'' comes from the Latin ''an'' ("not") and ''notatus'' ("marked"), and refers to the ray's coloration. The holotype is a male across, caught off Western Australia; several paratypes were also designated. Last tentatively placed the species in the genus ''Dasyatis'', noting that it belonged to the "maskray" species group that also included the bluespotted stingray (then ''Dasyatis kuhlii'').〔 In 2008, Last and William White elevated the ''kuhlii'' group to the rank of full genus as ''Neotrygon'', on the basis of morphological and molecular phylogenetic evidence.〔 }} }} }} }} }} In a 2012 phylogenetic analysis based on mitochondrial and nuclear DNA, the plain maskray and the Ningaloo maskray (''N. ningalooensis'') were found to be the most basal members of ''Neotrygon''. The divergence of the ''N. annotata'' lineage was estimated to have occurred ~54 Ma. Furthermore, the individuals sequenced in the study sorted into two genetically distinct clades, suggesting that ''N. annotata'' is a cryptic species complex. The two putative species were estimated to have diverged ~4.9 Ma; the precipitating event was likely the splitting of the ancestral population by coastline changes.〔 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「Plain maskray」の詳細全文を読む スポンサード リンク
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