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Yellow stingray
The yellow stingray (''Urobatis jamaicensis'') is a species of stingray in the family Urotrygonidae, found in the tropical western Atlantic Ocean from North Carolina to Trinidad. This bottom-dwelling species inhabits sandy, muddy, or seagrass bottoms in shallow inshore waters, commonly near coral reefs. Reaching no more than across, the yellow stingray has a round pectoral fin disc and a short tail with a well-developed caudal fin. It has a highly variable but distinctive dorsal color pattern consisting of either light-on-dark or dark-on-light reticulations forming spots and blotches, and can rapidly change the tonality of this coloration to improve its camouflage.
Relatively sedentary during the day, the yellow stingray feeds on small invertebrates and bony fishes. When hunting it may undulate its disc to uncover buried prey, or lift the front of its disc to form a "cave" attractive to shelter-seeking organisms. This species is aplacental viviparous, meaning that the developing embryos are sustained initially by yolk and later by histotroph ("uterine milk"). Females bear two litters of up to seven young per year in seagrass, following a gestation period of 5–6 months. Though innocuous towards humans, the yellow stingray can inflict a painful injury with its venomous tail spine. This species is taken as bycatch by commercial fisheries and collected for the aquarium trade; it may also be negatively affected by habitat degradation. Nevertheless, it remains common and widespread, which has led the International Union for Conservation of Nature (IUCN) to list it under Least Concern.
== Taxonomy and phylogeny ==
French naturalist Georges Cuvier originally described the yellow stingray as ''Raia jamaicensis'' in 1816, in ''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''. He based his account on specimens obtained from Jamaica, though no type specimens were designated.〔 Subsequent authors moved this species to the genus ''Urolophus'', and then to the genus ''Urobatis'' (some literature still refers to this species as ''Urolophus jamaicensis''). Other common names used for this ray include the yellow-spotted ray, the round ray, and the maid ray.〔
Nathan Lovejoy's 1996 phylogenetic analysis, based on morphology, found that the yellow stingray is the most basal member of a clade that also contains Pacific ''Urobatis'' species and the genus ''Urotrygon'' of Central and South America. This finding would render ''Urobatis'' polyphyletic, though further study is warranted to elucidate the relationships between these taxa.〔
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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