The name "purusii" originates from the species' type locality, the Purus river basin of Brazil, with a range that also extends into Peru.

There are no morphometric or coloration differences, but males may or may not demonstrate small hooks on the anal fin-rays during certain months of the year, specifically November.

[7] In later publications (1970 and 1993), French ichthyologist Jaqcues Géry reassigned it to the genus Iguanodectes based upon the differences in body shape.

Géry speculated that Steindachner considered all similar species to belong to Piabucus, and declined to include Iguanodectes in relevant taxonomical study.

[12] The lattermost factor has a documented negative effect on water quality, including increased levels of pesticides and fecal contamination.

[13] Nonetheless, I. purusii has a broad range that encompasses a good handful of river basins; thus, its population is likely to remain stable.