H. fimbriatus inhabits the Amazon River at Santarém and Rio Negro basin in Brazil and Venezuela.

[4] Fish of this genus have scaleless skin, three pairs of barbels (one maxillary and two mandibular), and small eyes located lateroventrally in a position about mid-length of the head.

The body is laterally compressed, bearing a long-based anal fin that runs from the anus to the anterior margin of the caudal peduncle.

[2] Hypophthalmus are unusual among Neotropical fishes in their habit of specialized plankton-feeding, collecting plankton by straining water over the fine sieve created by numerous long, thin gill rakers.

[5] H. edentatus is a pelagic species which lives in schools near the surface of the water over muddy bottoms.

H. edentatus has an emarginate caudal fin, which is less vulnerable to fin-nipping by piranhas which are more abundant in slow-moving waters.