The order Perciformes is the largest and most diverse of all fish orders, encompassing about 8,000 species. Distributed worldwide, fish of this order exist in both marine and freshwater habitats and represent species of diverse sizes, habitats, and behaviors. This order is broken into 150 families and 1,370 genera.
The suborder Scomproidei is divided into two families: the Xiphiidae and the Istiophoridae. These families have existed since the early Eocene period. The Xiphiidae family contains only one species, the broadbill swordfish (Xiphias gladius), distinguished from the Istiophoridae by a lack of pelvic fins and a long, flattened bill. Marlins belong to the family Istiophoridae. Members of this family are commonly referred to as "bill-fish." They have an elongated, rounded snout, called a bill, and live in tropical and subtropical seas. The Istiophoridae includes three genera and about 10 species. The three genera are: Istiophorus or sailfishes; Tetrapturus or spearfishes; and Makaira or marlins. The genus Makaira contains two species of marlin: the blue marlin and the black marlin. Marlins are different from the other two genera in that their dorsal fins do not measure in height as much as their bodies measure in depth. As with other fish in their family, the dorsal fins are long with many rays, and their tail has two sets of side keels.
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