Three pairs of barbels on rostral region, two pairs on lower jaw, one pair on posterior end of maxilla. End of maxilla barbel reaching pectoral fin insertion. A large saddle-shaped bony plate with rugose surface in front of dorsal fin. Anterior margin of this plate waved but no deep medial incision. No small crescentic bony plate between dorsal fin and large plate. Adipose fin base long, subequal to anal fin base length. Body yellow or gray-yellow dorsally, white ventrally.
Distribution:
Northeastern coasts of South America, from Guiana to Brazil.
Remarks:
A. proops also has a saddle-shaped bony plate before dorsal fin, but this species has deep medial incision on anterior margin of the plate. (Shimizu)