Redescription of Panaqolus purusiensis (LaMonte, 1935) (Siluriformes: Loricariidae) with identification key to the species of the genus

Despite Panaqolus purusiensis being described nearly 80 years ago, very little is known about it. The taxon was described based on a single specimen. Researching collection catalogues has revealed two more specimens that were caught together along with the holotype but had subsequently been deposited in different museums. Recent collections, including one from the type locality, have made more specimens available. Examination of this new material reveals that this species has three distinct color patterns that are size dependent. Specimens with standard length (SL) less than 30 mm show a coloration common among various species of Panaqolus consisting of regular bands on the body, fins and head. Specimens from 30-90 mm SL have a specific color pattern with thinner bands and those larger than 90 mm SL have a uniformly dark body with only the fins continuing to show bands. The most similar species are P. changae, P. gnomus, P. maccus, and P. nocturnus. The first three can easily be distinguished by their coloration and by body proportions. Specimens of P. nocturnus of more than 90 mm SL however are nearly indistinguishable from P. purusiensis of the same size, making identification difficult.