Odontesthes yucuman is diagnosed from other species of Odontesthes, except members of the O. perugiae species-group (O. bicudo, O. ledae, O. mirinensis, O. piquava and O. perugiae) by having the following combination of characters: teeth of the outer row on dentary and premaxilla shorter than those in the inner row (vs. teeth of outer row larger than those of inner row or teeth of outer and inner rows of equal size); origin of dorsal fin positioned over or posterior to anus (vs. anterior to anus); and 7 to 9 longitudinal scale rows above left and right lateral bands. It differs from O. bicudo, O. ledae, O. mirinensis, and O. piquava by having 19-25 lower branch gill rakers (vs. 26-29 in O. ledae, 24-29 in O. mirinensis, 25-31 in O. bicudo, and 27-28 in O. piquava); and from O. perugiae by the differences in the snout length (35.6-39.5, mean 37.7 vs. 28.6-37.4%, mean 32.2 of HL), and the distance between snout tip and posterior angle of labial ligament (31.3 -37.0, mean vs. 23.6 -33.1%, mean 28.2 of HL (Ref. 116661).

Description: First dorsal-fin rays iv-v; second dorsal-fin rays ii+7-8; anal-fin rays ii+13-15; pectoral-fin rays i+11-12; pelvic-fin rays i+5 (Ref. 116661).