This species is distinguished from all congeners, except Tetragonopterus ommatus by having a vertically-oriented patch of dark pigmentation limited to the posterior portion of the caudal peduncle (vs. mark centered on the caudal peduncle); differs from T. ommatus by the number of maxillary teeth 4-6 (vs. 7-8), with thinner and sharper dentary teeth (vs. more robust) and with greatest body depth 47.5-54.9% of SL (vs. 42.1-44.7% of SL); further differs from all congeners, except T. anostomus, T. denticulatus, T. juruena, T. rarus by the presence of five principal, sharper teeth on dentary (vs. three to four robust teeth); differs from T. anostomus by having a terminal mouth (vs. subsuperior mouth); differs further from T. anostomus, T. araguaiensis by the number of gill rakers of the first gill arch, lower and upper limbs, 13-15 and 8-10, respectively (vs. 17-20 and 10-13, respectively); differs from T. kuluene by having two humeral dark marks (vs. one); differs from T. argenteus by the predorsal scales 7-9 (vs. 11-18); differs from T. chalceus by bearing five thinner and sharper dentary teeth (vs. four robust teeth); differs from T. carvalhoi by the presence of a vertically-oriented dark mark on the caudal peduncle (vs. a lozenge-shaped dark mark); differs from T. rarus, T. georgiae by the presence of 3.5 scale rows between lateral line and pelvic-fin origin (vs. 4.5-5); differs from T. juruena by having 13-15 rakers on the lower limb of the first gill arch (vs. 10-12); differs from T. rarus by the absence of dark longitudinal stripes on the lateral surface of the body (vs. presence) (Ref. 118360).