This species is distinguished from its congeners in the Western Central Atlantic by the following characters: A III,9 in adults (II,10 in juveniles); differs from incilis by having fewer than 43 scales in the longitudinal serie; differs from hospes by having a deeper body, Ad 23.8-25.5% SL (vs. 21-23%), pectoral-fin rays 15-16 (vs. 13-14) and pectoral fin usually slightly shorter Pl = 17.3-18.9% SL, 72.3-82.9% Hl and Ps = 9-11 (vs. Pl = 21-24% SL, 80-96% Hl and Ps = 11-13). When alive M. rubrioculus can be easily distinguished from M. curema with its distinct reddish-orange iris (vs. none or indistinct in curema), the small goldish spot on the opercle (vs. a larger opercular spot) and has paler pigmentation on the flanks, without longitudinal bands (vs. flanks darker with ca. six bands). Further differs from curema by having a small spot at the dorsal part of the pectoral-fin base (spot deeper in curema, extending vertically down most of the base of the fin, and the fin tends to be pigmented darker on the fin rays and fin membrane) and these pectoral differences may also be seen in preserved specimens; anal fin is pale (vs. dark) and this difference is also evident when preserved; anterodorsal tip of second dorsal fin slightly darker than the other parts of the fin (vs. second dorsal fin is usually more uniformly dark); slightly darker anterodistal tip to the fin usually more distinct (vs. less distinct and may only be seen in some); caudal fin usually less heavily pigmented; scales on the flanks usually lack any minute, overlying, secondary scales, giving a smoother texture to the flanks (vs. usually with secondary scales (Ref. 58684).