The term billfish refers to a group of saltwater predatory fish characterised by prominent pointed bills (rostra), and by their large size; some are longer than 4 m (13 ft). Extant billfish include sailfish and marlin, which make up the family Istiophoridae; and swordfish, sole member of the family Xiphiidae. They are apex predators which feed on a wide variety of smaller fish, crustaceans and cephalopods. These two families are sometimes classified as belonging to the order Istiophoriformes, a group which originated around 71 million years ago in the Late Cretaceous, with the two families diverging around 15 million years ago in the Late Miocene. However, they are also classified as being closely related to the mackerels and tuna within the suborder Scombroidei of the order Perciformes. H