The Retzer's Elephant-nose Knifefish (Sternarchorhynchus retzeri) is a species of electric fish found in South America. This species is broadly distributed across the Amazon basin from the Rio Iça basin in the western portions of Amazonas, Brazil, to the Rio Trombetas in Pará, Brazil. Elephant-nose Knifefish live along the bottoms of rivers, actively preying on benthic invertebrates, including insect larvae. They have electrogenic abilities, using the generated electric field to aid in the location and capture of prey living in the mud, leaf litter, and other detritus. Their long snout aids in the capture of prey hiding in small crevices on the river floor. Their electrogenic abilities are also used for electrocommunication. (De Santana and Vari 2010).
Elephant-nose Knifefish are laterally compressed, with an elongated snout. The snout is generally straight, though it may have has a slight downward curve. Individuals of this species range between 300 and 400 mm, with females generally being larger than the males. They have dark pigmentation that generally reflects the surrounding environment. Anal and pectoral fins tend to be darker at the ends than the rest of the body. (De Santana and Vari 2010).