Pimelodus

1. A dark-brown transverse bar extending from nape almost to the pelvic fin origin; black longitudinal stripes on posterior half of flank; a dark-brown spot covering middle portion of dorsal fin rays ........................... P. ornatus

1’. Body with several small to large dark-brown rounded spots, aligned to form series or randomly distributed........ ............................................................................................. 2

2. Spots very small, randomly distributed, present only on dorsal portion of body; vomer with large patches of teeth ........................................................................ P. paranaensis

2’. Spots medium to large, aligned or not, present from dorsal region to ventral from lateral line; vomer toothless or with only a very small patch of teeth.............................. 3

3. Medium-sized spots usually smaller than the pupil, not aligned, fading into a diffuse longitudinal band from below adipose fin to end of caudal peduncle; interorbital distance contained 4.0 to 6.0 times in head length ............ ......................................................................... P. microstoma

3’. Large-sized spot usually equal to or larger than eye diameter, aligned (especially those immediately dorsal and ventral to lateral line), not fading posteriorly; interobital distance contained 2.5 to 3.8 times in head length ............. 4

4. Serration present in the basal two thirds or more of the anterior margin of pectoral spine, well developed; a small patch of teeth present on vomer; interorbital distance contained 2.5 to 3.4 times in head length........ P. mysteriosus 4’. Serration present in the basal one half or less of the anterior margin of pectoral spine, poorly developed; vomer toothless; interorbital distance contained 3.3 to 3.8 times in head length .......................................... P. maculatus