Wikipedia
Hypopomidae
The Hypopomidae are a family of fishes in the order Gymnotiformes known as the bluntnose knifefish. They may also be called grass or leaf knifefishes. These fish are not often eaten, of little commercial importance, rarely kept as aquarium fish, and poorly studied; however, species in this family may constitute a significant fraction of the biomass in the areas they inhabit.
These fish originate from fresh water in Panama and South America. The Hypopomidae are confined to the humid neotropics, ranging the Río de la Plata of Argentina (35°S) to the Río Tuira of Panama (8°N). Hypopomids are known from the continental waters of all South American countries except Chile, and are most diverse in the Amazon Basin.