Gonostomatidae

The Gonostomatidae are a family of mesopelagic marine fish, commonly named bristlemouths, lightfishes, or anglemouths. It is a relatively small family, containing only eight known genera and 32 species. However, bristlemouths make up for their lack of diversity with numbers: Cyclothone, with 12 species, is thought to be (along with Vinciguerria), the most abundant vertebrate genus in the world, numbering in the hundreds of trillions to quadrillions.

The fossil record of this family dates back to the Miocene epoch. Living bristlemouths were discovered by William Beebe in the early 1930s and described by L. S. Berg in 1958. The fish are mostly found in the Atlantic, Indian, and Pacific Oceans, although the species Cyclothone microdon may be found in Arctic waters. They have elongated bodies from 2 to 30 cm (0.79 to 11.81 in) in length. They have a number of green or red light-producing photophores aligned along the undersides of their heads or bodies. Their chief common name, bristlemouth, comes from their odd, equally sized, and bristle-like teeth. They are typically black in color which provides camouflage from predators in deep, dark waters.