oceansoftheworld:

The pelagic stingray (Pteroplatytrygon violacea) is a species of stingray in the family Dasyatidae. The pelagic stingray is easily distinguished by its characteristic, serrated tail spine which is flattened and attached rigidly to the skin of the tail. Cells at the base of the spine secrete a poison which can inflict exceedingly painful wounds.  It is possible, as with other members of the family Dasyatidae, that new spines develop before an old one is lost. The body of the pelagic stingray is disc-shaped and depressed but thick, with a blunt, rounded snout and angular pectorals. The mouth is small and curved, and filled with bands of small, rounded teeth with cusps, ridges, or tubercles. Pelagic stingrays have no prominent markings on their skin, and vary in color from uniformly violet or purple to dark blue-green, both on their dorsal and ventral surfaces. As its name suggests, the pelagic stingray occupies open surface and near surface waters, usually occurring in the first 100 m of the water but reaching depths of 381 m.  It is often reef-associated, and is perhaps the only totally pelagic member of the family Dasyatidae. Traditionally, spines of members of this family (Dasyatidae) were used for spear tips, awls, and daggers, and are currently sold as curios.  However, the pelagic stingray is of no great commercial importance, and – due to its pelagic existence - comes into contact with humans only rarely.

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