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Stenidae (order Cetacea, suborder Odontoceti) A family of small, porpoise-like mammals in which the snout is long and merges into the forehead, the dorsal fin is hooked, and the tail is slightly notched at the mid-line. Members of the Stenidae attain lengths of about 2 m. There are four species, in three genera. Steno (rough-toothed dolphin) is distributed throughout the tropical and warm-temperate oceans. Sotalia (the tucuxi) occurs around the coast of S. America and in the rivers Amazon and Orinoco. Sousa (the white or hump-backed dolphin) occurs in coastal waters around Africa and southern Asia. Many authorities include the three genera in the Delphinidae.