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The External Anatomy of a SharkThe external anatomy of sharks varies considerably between the approximately 370 known species. The diagram above does not represent any one species of shark, but rather is a compilation of the features posessed by many different species. While bottom-dwelling (benthic) sharks may posess spiracles to enable them to breathe easier while sitting on the bottom, open ocean (pelagic) sharks that swim continually do not posess them. However, there are many features shared by all sharks.The skin of all sharks posess small dermal denticles known as placoid scales, which give the shark its rough, sometimes sandpaper-like texture. In fact, shark skin has been used in many cultures as a good subtitute for sandpaper. You may notice that the scales look like small shark teeth. This is because that is exactly what they are! Actually, it is believed that the teeth of sharks evolved from modifications of scales, so I guess it would be better to say that shark teeth are actually scales! Shark skin is also very tough and pliable. When properly cured, shark skin has been made into fine leather goods such as purses, shoes, boots, and wallets.
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