Wikipedia
Distichodontidae
The Distichodontidae are a family of fresh water African fishes of the order Characiformes.
Two evolutionary grades are found in this family; micropredators ( predators of very small organisms) and herbivores have a nonprotractile upper jaw and a deep to shallow body, while carnivores have a movable upper jaw and an elongated body. The fish vary greatly in size among species, with the micropredators being less than in length, and the largest carnivores can reach up to .