This species differs from its congeners in the Río de La Plata and coastal basins of southern Brazil, except A. abilhoai, A. agostinhoi, A. formoso, A. multispinis and A. taunayi, by possessing a maxillary barbel short and not free from lower lip (vs. longer and free from lower lip); from A. abilhoai by the width of its mandibulary teeth row 16.5-21.0% of HL (vs. 13.4-15.5%) and 39.3-58.0% of interorbital width (vs. 32.9-37.9%); from A. agostinhoi by occipital depth 15.4-18.8% of SL (vs. 18.8-22.0%) and head length 34.4-37.9%, mean= 36.3% of SL (vs. 37.8-41.4%, mean= 38.9%); from A. formoso by orbital diameter 11.9-18.4% of HL (vs. 8.3-8.7%), caudal peduncle depth 8.8-11.5% of SL (vs. 7.8-8.7%) and number of dentary teeth 51-97 (vs. 110); from A. multispinis and A. taunayi by number of interopercular spines 12-22 (vs. 24-35 and 22-28, respectively) (Ref. 83296).