This species is distinguished from its congeners by the exclusive set of three characters: nostrils large; tube of anterior nostril distinctly large, with tip surpassing well the vertical through snout tip, and posterior nostril as large as the eye, about 90 % of orbital diameter (vs. nostrils smaller; the tube of anterior nostril shorter, with its tip not reaching or reaching the vertical through snout tip, and posterior nostril much smaller than the eye, about half the orbital diameter); smaller interorbital width 38-40% HL (vs. 40-67, except in M. pleriqueater); and with dark brown saddles diffuse on the predorsal, subdorsal, and subadipose regions (vs. dark brown saddles well-delimited, except in M. variegatus and M. eurystoma); differs further from M. leptostriatus, its most similar species and from the same drainage system, by the following features not having a light transverse band on the nuchal region (vs. presence of a thin and sinuous light band), dorsal, anal, and caudal fins without stripes (vs. each fin with a brown stripe on middle portion), epibranchial 1 with 2 gill rakers (vs. usually 1); smaller number of gill rakers on the first branchial arch 5-6 (vs. 6-9), anal fin when depressed reaching the first ventral procurrent caudal-fin rays (vs. not reaching), and more anal-fin rays 12 (vs. 9-11); further distinguished by the presence of a dark stripe on the axis of gill filaments and greater caudal peduncle length 17.1-18.5% SL (vs. 10.0-16.9 in M. carlae, M. cibelae, M. cottoides, M. eurystoma, M. garavelloi, M. iheringi, M. leptostriatus, M. maculatus, M. malabarbai, M. minutus, M. nigripinnis, M. parahybae, M. pataxo, M. pellopterygius, M. pleriqueater, M. poecilus, M. secundus, M. variegatus) (Ref. 130492).