This species is distinguished from its congeners by the following characters: presence of iii,9 rays in the dorsal-fin (vs. ii,9); from most congeners by having 2 humeral spots, in which the first one is vertically elongate (except in M. diamantina, M. diktyota, M. eigenmanni, M. inrai, M. levidorsa, M. moisae, M. naponis, M. pankilopteryx, and M. surinamensis) (vs. absent, or horizontally elongate or diffuse humeral spot); differs from the remaining species by the number of branched anal-fin rays 17-19 (vs. 20-35); from M. diktyota, M. eigenmanni, M. georgiae, M. inrai, M. levidorsa, M. moisae, and M. naponis by the number of the lateral line scales, 36-37 (vs. 41-47 in M. moisae and 31-35 in the remaining species); from M. pankilopteryx by the number of maxillary teeth 4-5 (vs. 2-3) and the shape of the caudal peduncle spot which is vertically elongate (vs. horizontally elongate in M. pankilopteryx) (Ref. 86678).