The Amiidae are a family of basal ray-finned fishes. The bowfin is the only species to survive today, although additional species in all four subfamilies of Amiidae are known from Jurassic, Cretaceous, and Eocene fossils. Bowfins are now found throughout eastern North America, typically in slow-moving backwaters, canals, and ox-bow lakes. When the oxygen level is low (as often happens in still waters), the bowfin can rise to the surface and gulp air into its swim bladder, which is lined with blood vessels and can serve as a primitive lung.