Any of about 13 species of cetaceans in the suborder Mysticeti. They are distinguished by a specialized feeding structure, the baleen, which strains plankton and small crustaceans from the water. It consists of two horny plates attached to the roof of the mouth. Each plate (as long as 12 ft, or 3.6 m, in the right whale) is composed of parallel slats with fringes that mat together to form a sieve. Other baleen whales are the blue, fin, gray, humpback, and sei whales and the rorqual. Baleen was once used for corset stays and is still used in some industrial brushes.