Stegostenopos cryptogenes
Stegostenopos cryptogenes is a species of bluntnose knifefish endemic to Brazil where it is found in the Rio Negro basin.  This species can reach a total length of up to . It is the only member of the genus Stegostenopos according to FishBase, but studies have shown that it belongs in Hypopygus (making Stegostenopos a junior synonym) and this is followed by the Catalog of Fishes.

References

Hypopomidae
Fish described in 1997
Knifefish of Brazil
Endemic fish of Brazil