Pseudancistrus asurini is distinguished from all congeners by having whitish dorsal-and caudal-fin tips (vs. entirely dark). It can be further separated from P. reus and P. kayabi by having conspicuous whitish spots on the body (vs. body mottled or with bars in P. reus and with whitish spots that fade along the body and can cover more than one plate in P. kayabi). It also differs from P. depressus and P. barbatus by having the snout with yellowish odontodes (vs. reddish-brown) and from P. nigrescens, P. corantijniensis, and P. zawadzkii by having smaller whitish spots covering the body which increase gradually in size on the head (diameter 0.3?0.8 mm) and further on the body (diameter 0.7?1.3) (vs. spots abruptly increasing size between the head (diameter 1.1?1.3) and the body (di¬ameter 2.6?2.3 mm). Other characters useful to identify this new species include the following: shorter predorsal length, 39?43% SL (vs. 43?46% in P. zawadzkii and 43?45% in P. nigrescens); smaller dorsal pectoral depth, 23?27% SL (vs. 27?31% in P. zawadzkii); smaller caudal pe¬duncle depth, 9?11% SL (vs. 13?14% in P. zawadzkii and 13% in P. nigrescens); short¬er barbel, 5?9% HL (vs. 10?11 in P. nigrescens); and head depth, 57?66% SL, which is smaller than in P. zawadzkii (67?73%) but greater than in P. barbatus (41?53%) (Ref. 99871).