This species is easily distinguished from all congeners, except A. jataiensis, A. parecis, A. reisi, and A. tombador by the absence of an adipose fin which is replaced by a series of 3 to 5 median, unpaired platelets forming a low postdorsal ridge. It also differs from all congeners in lacking an adipose fin, except for A. tombador, by the naked margin of snout broad and the reduced development of snout tentacles in both sexes (usually absent), and by the presence of two or more plates of the dorsal plate series between

the end of the postdorsal ridge and the origin of the first dorsal procurrent caudal-fin (vs. one or none). This species is distinguished from A. tombador by the head depth at supraoccipital (17.9-19.3 vs. 15.6-16.9% SL), cleithral width (31.4-33.1 vs. 27.5-31.2% SL), interorbital width (15.9-16.8 vs. 12.7-15.1% SL), and by the base of the first anal-fin pterygiophore covered by skin (vs. exposed) (Ref. 56914).