Members of the order have two dorsal fins, which usually possess spines, no anal fin or nictitating membrane, and five gill slits. In most other respects, however, they are quite variable in form and size. They are found worldwide, from polar to tropical waters, and from shallow coastal seas to the open ocean.
Family Centrophoridae Bleeker, 1859 (gulper sharks)
Family Dalatiidae (J. E. Gray, 1851) (kitefin sharks)
Family Echinorhinidae Theodore Gill, 1862 (bramble sharks)
Family Etmopteridae Fowler, 1934 (lantern sharks)
Family Oxynotidae Gill, 1872 (rough sharks)
Family Somniosidae D. S. Jordan, 1888 (sleeper sharks)
Family Squalidae Blainville, 1816 (dogfish sharks)