They are dark brown to black fish, with shortened, deep bodies. They are characterised by a large mouth and sharp prominent teeth, which prevent them from closing their mouths. They are covered with thin scales and spines. Juveniles are quite different to adults and were once mistaken for a separate species.
A large lateral line along each side of the body detects movements from nearby prey.
They are distributed worldwide.
This is a deep sea fish, typically found from 500 - 2,000m (6,500ft), but they may occur to depths of 5,000m (16,400ft)
These fish feed on crustaceans when young and mainly fish and shrimp in adulthood.
They may occur as solitary animals or in schools.