Relative to body length, the fangtooth carries the largest teeth of any known fish. The pair at the front of the lower jaw are long enough that they would strike the roof of the skull if the jaw simply hinged shut. Instead they pass into paired sockets flanking the brain case, an arrangement that has been described repeatedly in the anatomical literature.
The teeth suit a life of infrequent meals. Prey in the deep sea is sparse, and a fangtooth cannot afford to lose an encounter, so the design favours holding whatever it catches rather than chewing. Reported diet includes crustaceans and small fishes.
Juvenile fangtooths are a separate puzzle. They bear long head spines, feed by filtering small crustaceans, and were originally described under the name Caulolepis before their identity as young Anoplogaster was recognised. The change in form between juvenile and adult is among the more dramatic in deep-sea fishes.