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(genus Heterodontus), any member of the only genus in the family Heterodontidae (class Selachii), characterized by a large, heavy spine on the anterior edge of each dorsal fin. There are about 10 marine, bottom-dwelling species of these sharks, which are found almost everywhere except in the Mediterranean and Atlantic. Horned sharks may grow to 1.4 m (5 feet) long. Their jaws are covered with sharp teeth, incisor-like ones in the front and large molar-like ones on the sides. They feed on invertebrates such as sea urchins and crustaceans.