Malacosteidae
by R. H. Gibbs, Jr.
Jaws long, extending almost to posterior margin of head; floor of mouth open, no membrane connecting right and left halves of lower jaw to isthmus; lower jaw with long fangs, much longer than any upper jaw teeth; chin barbel present or absent. Dorsal and anal fins located at hind end of body near tail, their bases about equal in length, their origins approximately opposite; no dorsal adipose fin; pelvic finrays 6. Two rows of prominent photophores on ventral part of body on each side, the photophores either evenly spaced or in separated groups (reduced in size and difficult to see in Malacosteus); numerous small photophores on most of body and head, most dense ventrally; in addition to post-orbital luminous organ, a pre-orbital or sub-orbital organ present. No scales. Body usually black.
Fairly common in deep oceanic waters; mesopelagic or bathypelagic, usually living deeper than 500 m during the day; some individuals of some species migrating to shallower depths at night. Feeding habits poorly known, food including midwater fishes and crustaceans. Lower jaw can be thrust far forward, in the manner of a dragonfly larva, to impale prey on its long anterior fangs.
Genera 3; in Clofnam area 3.
Recent revisions: Regan and Trewavas (1930), Morrow (1964), Goodyear (unpublished Ph.D. thesis, 1980).