Aspidoras gabrieli is diagnosed from all congeners by having densely pigmented rays and interradial membranes of the dorsal and pectoral fins, from base to tip in young individuals, with a gradual reduction in pigmentation on the fin extremities over the course of ontogeny, though the base remains densely pigmented in larger individuals (vs. dorsal and pectoral fins pale or with little pigmentation on base). It differs also from all congeners by having the inner bony margin of the pectoral spine expanded as a narrow laminar shelf with edge smooth or scarcely serrated (vs. posterior margin totally or partially covered with sharp serrations or totally smooth and without a laminar shelf in A. albater and A. eurycephalus). It can be further separated from other congeners, except A. taurus, by the absence of a lateral-line canal posterior to the two anterior lateral-line ossicles (vs. presence of lateral-line canal in at least one dorsolateral plate posterior to the ossicles). It differs also from congeners, except A. velites and A. psammatides, by having the predorsal region naked, with contralateral dorsolateral plates not meeting each other on the dorsal midline at any ontogenetic stage (vs. predorsal region covered by dorsolateral plates). It is further distinguished from its congeners (except A. maculosus, A. albater, A. lakoi, and A. depinnai) by having large, oval, brown spots on the flank and caudal peduncle that sometimes merge to form irregular patches (vs. large oval spots absent). It can be distinguished from A. poecilus, A. fuscoguttatus, A. rochai, A. albater, A. depinnai, and A. virgulatus by the presence of two pores along the nasal sensory canal (vs. three pores). It further differs from other species of Aspirdoras by the following characters: pelvic-fin rays i,5 (vs. i,6 in A. albater); preadipose azygous plates 2-4 (vs. 5 in A. albater; 6-13 in A. lakoi), pectoral-fin rays I,9 (vs. I,8 in A. albater and A. maculosus), length of the pectoral-fin ray 8.0-12.1 times in SL (vs. 5.0-7.3 in A. albater ), and body depth 2.9-3.6 times in SL (vs. 3.7-4.2 in A. albater; . 3.8-4.0 in A. maculosus); length of the pectoral spine, 8.0-12.1 times in SL (vs. 5.5-7.0 in A. maculosus; 6.0-7.0 in A. lakoi ), and orbital diameter, 6.2-11.0 times in HL (vs. 3.5-4.5 in A. maculosus); length of the maxillary barbel, 17.4-25.6% SL (vs. 4.1-15.3% in A. depinnai); horizontal diameter of the orbit, 8.2-14.3% HL (vs. 15.5-20.8% in A. depinnai); and absence of bifid serrations on the pectoral spine (vs. presence in A. depinnai); and absence of serrations on the posterior margin of the pectoral spine (vs. presence in A. lakoi) (Ref. 96502).

Description: Anal fin i,6-8, pelvic fin i,5 (Ref. 96502).