Distinguished from all congeners except Ancistrus tombador and A. jataiensis by the absence of an adipose fin. Adipose fin is replaced by a series of 2 to 4 median unpaired platelets forming a low crest. These platelets are nearly immediately followed by the plate-like procurrent caudal rays, while in A. tombador these are followed by at least two lateral plates that join dorsally before the procurrent caudal rays (Ref. 54498). Distinguished from A. tombador by following characters: snout with naked margin generally ill-delimited by posterior dermal plates which are irregular in size and shape and rarely joined together; tentacles present, unbranched; body wider (cleithral width 31.6-34.5% SL, mean 33.1) and caudal peduncle depth 9.6-10.7% SL, mean 10.2. Differs from A. jataiensis by the following morphometric characters: predorsal length (43.8-46.4% SL, mean 44.9, vs. 47.5-49.3% SL, mean 48.1), occipital depth (14.9-17.0% SL, mean 16.0, versus 17.0-19.5% SL, mean 18.1) and caudal peduncle length (27.7-30.9% SL, mean 28.7, vs. 24.6-27.1%SL, mean 26.3) (Ref. 54498).

Description: D i,7; P i,6; V i,5; A i,4; C i,13,i or more generally i,14,i (Ref. 54498).