Hoplias curupira, also known as the black wolf-fish, has a wide distribution in the Amazon basin but was described as recently as 2009. The fish is named after Curupira, a mythical creature of Brazilian folklore that protects the forest and it's inhibitants, sometimes taking the form of a small Amerindian child whose feet are turned backwards, making it difficult to follow its tracks. It is a medium-sized fish but relatively bulky in build compared to other Hoplias with a blunt head and broad body. The colour of the fish changes according to mood from a light brown patterning to an almost solid black colouring leading to the common English name of Black Wolf-fish. In captivity the average size is 16 inches but wild specimens have been reported at up to 30 inches.