Moenkhausia lineomaculata can be easily diagnosed from all congeners, except M. cosmops, M. cotinho, M. diktyota, M. forestii, M. oligolepis, M. sanctaefilomenae, and M. pyrophthalma by having a reticulated color pattern on body formed by dark pigmentation on the posterior portion of the scales (vs. absence). It further differs from all congeners, except M. cosmops, M. cotinho, M. forestii, M. oligolepis, M. sanctaefilomenae, and M. pyrophthalma by having a light area preceding the dark caudal peduncle blotch (vs. absence). It is distinguished from all the aforementioned species, except M. cotinho by having longitudinal series of dark dots on body (vs. absence), and from M. cotinho by the humeral blotch evenly pigmented along its length (vs. dorsal portion of the humeral blotch distinctly darker) and by having the longitudinal line formed by subjacent dark pigmentation along horizontal septum starting approximately at the vertical through dorsal-fin origin (vs. starting slightly posterior to the humeral blotch) (Ref. 104871).

Description: Dorsal-fin rays ii,9; anal-fin rays iv-v,16-18; pectoral-fin rays i,10-12; pelvic-fin rays i,7-8; lateral line completely pored, with 31, 32, or 33 perforated scales on longitudinal series or incomplete with 12 perforated scales and total of 31 scales on longitudinal series (Ref. 104871).