The footballfish form a family, Himantolophidae, of globose, deep-sea anglerfishes found in tropical and subtropical waters of the Atlantic, Indian, and Pacific Ocean. The family contains about 22 species all in a single genus, Himantolophus (from the Greek imantos, "thong, strap", and lophos, "crest").
As in most other deep-sea anglerfish families, sexual dimorphism is extreme: the largest females may exceed lengths of 60 centimetres (24 inches) and are globose in shape, whereas males do not exceed 4 cm (1+1⁄2 in) as adults and are comparatively fusiform. Their flesh is gelatinous, but thickens in the larger females, which also possess a covering of "bucklers" — round, bony plates each with a median spine — that are absent in males. Both are a reddish brown to black in life.
In females, the mouth is large and oblique. The subequal jaws are anteriorly lined with rows of numerous close-set, depressible, and retrorse teeth; vomerine teeth are absent. Footballfish females differ from those of other ceratioid families by their shortened, blunt snout; along with the chin, it is covered in sensory papillae. Originating above or slightly in advance of the small eye is an illicium (the "fishing rod") and at its end a bioluminescent, bulbous esca (the "fishing lure", its light owing to symbiotic bacteria). Escal morphology varies between species, and it may or may not possess denticles or accessory appendages, the latter either branched or unbranched. The pterygiophore of the illicium does not protrude from the snout, and there is no hyoid barbel.
At maturity, the streamlined males have an enlarged posterior nostril (with 10–17 lamellae); slightly ovoid eye with an enlarged pupil creating a narrow anterior aphakic space; no ilicium or esca; and the head and body is covered in dermal spinules, those along the snout midline being enlarged. The jaw lacks teeth, whereas those of the denticular bone have fused into a larger mass; the upper denticular bone possesses 10–17 hooked denticles.
In both sexes, the fins are spineless: the single dorsal fin with 5–6 soft rays, the pectoral fins with 14–18, the anal fin with four, and the caudal fin with 19. There are six branchiostegal rays and 19 vertebrae; the parietal is lacking throughout life, there are no epurals, and the pelvic bone is triradiate.
The footballfish was first discovered in 1837 by Johan Reinhardt. Their poor musculature and cumbersome morphology indicate that mature female footballfish are probably poor swimmers and largely sedentary, lie-in-wait predators. They are primarily mesopelagic, living in open water, with very few caught below 1,000 metres (3,300 feet; 550 fathoms). Females are carnivorous and feed upon other pelagic fish (such as lanternfishes and ridgeheads) and cephalopods, as well as shrimp and euphausiids that are presumably attracted to within striking distance by the footballfish's luminous lure.[citation needed]