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The Triakidae or houndsharks are a family of ground sharks, consisting of about 40 species in nine genera. In some classifications, the family is split into two subfamilies, with the genera Mustelus, Scylliogaleus and Triakis in the subfamily Triakinae, and the remainders in the subfamily Galeorhininae. Houndsharks are distinguished by possessing two large, spineless dorsal fins, an anal fin and oval eyes with nictitating eyelids. They are small to medium in size, ranging from 37 to 220 cm in adult length. They are found throughout the world in warm and temperate waters, where they feed on small fish and invertebrates on the seabed and in midwater.