Black seadevils are small, deepsea lophiiform fishes of the family Melanocetidae. The five known species (with only two given common names) are all within the genus Melanocetus. They are found in tropical to temperate waters of the Atlantic, Indian, and Pacific Oceans, with one species known only from the Ross Sea.
One of several anglerfish families, black seadevils are named for their baleful appearance and typically pitch black skin. The family name Melanocetidae may be translated from the Greek melanos meaning "black", and cetus meaning either "whale" or "sea monster". The humpback anglerfish (Melanocetus johnsonii) was featured on the August 14, 1995, issue of Time magazine, becoming something of a flagship species of deepsea fauna.
The currently recognized species in this genus are:
Black seadevils are characterised by a gelatinous, mostly scaleless, globose body, a large head, and generous complement of menacingly large, sharp, glassy, fang-like teeth lining the jaws of a cavernous, oblique mouth. These teeth are depressible and present only in females. Some species have a scattering of epidermal spinules on the body, and the scales (when present) are conical, hollow, and translucent. Like other anglerfishes, black seadevils possess an illicium and esca; the former being a modified dorsal spine—the "fishing rod"—and the latter being the bulbous, bioluminescent "fishing lure". The esca is simple in black seadevils (with either a conical terminus or anterior and posterior ridges in some species), and both it and the illicium are free of denticles.