Polyodontidae - (Paddlefishes)
Distribution: China and United States. Snout resembling a paddle and with minute barbels. Body scaleless (naked) except for a few scales on caudal peduncle. Heterocercal caudal fin. Gill rakers long and numerous (hundreds) in the planktivorous Polyodon. Minute teeth. Spiracle present. Operculum greatly extended posteriorly. Mouth protrusible or nonprotrusible. Two monotypic genera (Polyodon and Psephurus). Exhibited in public aquaria and used for food. Both species are under threat.