Geographical Distribution: Amazon, Araguaia-Tocantins (Hydrolycusscomberoides e Raphiodonvulpinus) and Prata/Pantanal (Raphiodonvulpinus) basins.

Description: Fish with tiny scales. Silver coloration, oblique mouth, large pectoral fins, elongated and laterally compressed body, and H. Scomberoides is taller and has a round black spot behind the operculum. Both species are known as “cachorra” in Portuguese, which means “dog”, because of the presence of a pair of fangs in the jaw. These fangs are so large that the top of the head has two holes to accommodate them when the mouth is closed. These species can reach 1,64ft in length. 

Ecology: Mid-water fishes, occurring in the canals and beaches of rivers, lakes and flooded forests. They are piscivores which attack relatively big preys, sometimes reaching about 40% to 50% of the predator’s length. They migrate for long distances toreproduce and have no commercial importance.