"four" and meaning "tooth" and the Latin forma meaning "shape". Counting these teeth-like bones is a way of distinguishing similar families, for example, the Tetraodontidae ("four-toothed"), Triodontidae ("three-toothed"), and Diodontidae ("two-toothed"). Their jaws are aided by powerful muscles, and many species also have pharyngeal teeth to further process prey items, because the Tetraodontiformes prey mostly on hard-shelled invertebrates, such as crustaceans and shellfish. The Molidae are conspicuous even within this oddball order; they lack swim bladders and spines, and are propelled by their very tall dorsal and anal fins. The caudal peduncle is absent and the caudal fin is reduced to a stiff rudder-like structure. Molids are pelagic rather than reef-associated and feed on soft-bodied invertebrates, especially jellyfish. Families This cladogram of extant Tetraodontiformes is based on Santini et al., 2013. Fossil families Superfamily †Plectocretacicoidea Tyler & Sorbini, 1996 †Cretatriacanthidae Tyler & Sorbini, 1996 †Plectocretacicidae Tyler & Sorbini, 1996 †Protriacanthidae Tyler & Sorbini, 1996 †Bolcabalistidae (e.g. Eospinus) Santini & Tyler, 2003 †Eoplectidae †Moclaybalistidae Santini & Tyler, 2003 †Spinacanthidae Timeline of genera References Tree of Life: Tetraodontiformes Extant Cenomanian first appearances