Dasyatis sp.

Whip ray dermal denticle. Dermal denticles are structures found on the body surface of many insects y cartilaginous fish.

In cartilaginous fish the denticles replace the function of the scales. The denticulated skin of sharks can be as rough as a sandpaperHowever, the scratchy texture is only felt when you slide your hand in the direction from tail to head. If done in the opposite direction, it produces a soft sensation. It has been observed that sharks use the texture of their skin to inflict wounds on their prey.

The function of the denticles is to create a barrier against the water to facilitate swimming, and they also allow sharks to swim silently so as not to be detected by prey and/or other predators. 

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