Acantopsis dinema is distinguished from all congeners by the combination of the following characters: absence of large spots on side of head; many black specks beneath midlateral row of black spots from head to caudal fin; 2 pairs of labial barbels; absence of distinct small black spot on upper margin of caudal-fin base; absence of large black spots on dorsal or caudal fins; dorsal fin usually with 10½ branched rays and pectoral fin with 10 rays; 8-17 dark saddles along dorsal midline; 6-12 black spots along side of body; 41-42 total vertebrae; and body depth 12.0-14.5% SL, body width 8.0-10.3% SL, caudal-peduncle length 12.1-14.3% SL (Ref. 116755).