Largest teeth relative to head size - fish
Chauliodus sloani (Viperfish)
United States ()

Relative to its head size, the fish with the largest teeth is Sloan's viperfish (Chauliodus sloani) which has teeth so large it must open its mouth to make the jaws vertical before it can swallow prey. When the mouth is closed, the teeth overlap the jaws. It eats large prey by lowering the internal skeleton of the gills, allowing the prey to pass into the throat without interference. It can impale prey on the teeth by swimming at them with the first vertebra behind the head acting as a shock absorber. Sloan's viperfish is approximately 28 cm (11 in) long. Its head is about 2 cm (0.8 in) and its teeth are just over half this length.

The sides of the viperfish's body are covered with hexagonal pigmented areas, each with one or more small photophores (light-producing organs). Like many other species of deepsea fishes, Viperfish vertically migrate. During the day they are found in deep water (500–2,500 m or 1,640–8,200 ft) but at night these fish swim up into shallower water (less than 600 m or 1,970 ft depth) where food is more plentiful. It feeds mostly on crustaceans and small fishes. The first dorsal fin has light organs which are believed to attract prey.