Distinguished from all congeners except Ancistrus tombador and A. reisi 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. tomabador these are followed by at least two lateral plates that join dorsally before the procurrent caudal rays. It further differs from A. tombador by the 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, some branched in larger males; body wider (cleithral width 33.6-35.6% SL, mean 34.9) and caudal peduncle depth 10.1-10.7% SL, mean 10.4. Differs from A. reisi by the following morphometric characters: predorsal length (47.5-49.3% SL, mean 48.1, vs. 43.8-46.4% SL, mean 44.9), occipital depth (17.0-19.5% SL, mean 18.1, versus 14.9-17.0% SL, mean 16) and caudal peduncle length (24.6-27.1% SL, mean 26.3, vs. 27.7-30.9%SL, mean 28.7) (Ref. 54498).

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