Characters that diagnose Odontostilbe ecuadorensis are: (1) upper gill rakers 5-6, lower 9-11, mostly 10-11 (vs. upper gill rakers 6-8, mostly 6-7, and lower 11-14, usually 12 in

O. fugitiva; (2) denticulation of gill rakers more numerous in O. ecuadorensis than in O. fugitiva (in specimens

larger than 32.5 mm SL), mainly on posteriormost gill raker of lower arch (5-6 denticles on basal portions of gill raker in O. ecuadorensis vs. 0-2 in O. fugitiva; (3) elongate 2nd unbranched dorsal-fin ray (vs. not elongate in O. euspilura and very short elongate in O. pulchra); (4) no hooks on unbranched pelvic-fin ray (vs. 1-2 unpaired hooks per segment on 1st unbranched pelvic-fin ray occasionally present in O. euspilura and O. pulchra); (5) 1-3 paired or unpaired hooks per segment on last unbranched anal-fin ray, and 1st to 16th anal-fin branched rays (small hooks like knots on anal-fin ray branches, usually on 10th branched fin ray and following rays) (vs. well-developed hooks on 1st to 22nd anal-fin branched rays at distal half length of fin rays in O. pulchra); and (6) usually seven large dentary teeth, with seven cusps (vs. 4 large dentary teeth with 3 large and compressed central cusps and 2, 3 lateral small cusps in O. pequira). Odontostilbe ecuadorensis differs from sympatric O. euspilura by its terminal mouth (vs. subterminal mouth).