Fangtooths are beryciform fish of the family Anoplogastride (sometimes spelled the "Anoplogasteridae") that live in the deep sea. With a total circumglobal distribution in tropical and cold-temperate waters, the family has no known close relatives.

They are named for their disproportionately large, fang-like teeth and their unapproachable visage, fangtooths are actually quite small and harmless to humans: the larger of the two species, the common fangtooth, reaches a maximum length of just 16 cm (6.3 in), the shorthorn fangtooth is less than half this size though currently known only from juvenile specimens.

The head is small with a large jaw and appears haggard, riddled with mucous cavities delineated by serrated edges and covered by a thin skin. The eyes are relatively small, set high on the head; the entire head is a dark brown to black and is strongly compressed laterally, deep anteriorly and progressively more slender towards the tail. The fins are small, simple, and spineless; the scales are embedded in the skin and take the form of thin plates.

Fangtooths are among the deepest-living fish, found as far as 5,000 m (16,000 ft) down. They are more commonly found between 200 and 2,000 m (660 and 6,560 ft). By day these fish remain in the gloomy depths and towards evening they rise to the upper layers of the water column to feed by starlight, returning to deep water by daybreak.

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