Placoid scales are found in rays and sharks. These structures provide protection, camouflage, and hydrodynamic advantages. They provide protection from the environment and from predators. Sharks and rays belong to the group of organisms called elasmobranch. Unlike the bony fish, elasmobranchs are characterized by a cartilaginous skeleton. Placoid scales are often referred to as denticles.
Besides placoid scales, other types of scales exist such as ganoid scales, ctenoid scales and cycloid scales.
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