Attains a total length (including the tail fin) of about 2 ft, 5 in (72 cm) and a weight of 9 lb (4 kg). The head and body are deep, very compressed, and shaped like an oblong disc, or dinner platter; juveniles are diamond-shaped. The body, cheeks, and operculum are covered with vertically elongated scales. The mouth is small, and the maxilla has two or three ridges, bound to the ascending processes of the premaxillae and loosely connected to the palatines. The jaws have one or two rows of minute, slender teeth, and the vomer may or may not have three or four minute, slender teeth. There are two dorsal fins, the first with six to seven spines and the second with 31-34 unbranched soft rays. The anal fin has two spines and 33-35 unbranched rays. The tail fin has 13 branched rays. The pelvic fins have one spine and six branched rays; there is a row of 34-36 small spines along each side of the dorsal and anal fin bases.
Juveniles have a greatly elongated first anal fin spine and second dorsal fin spine. The pelagic juvenile stage (4-8 in, or 10-20 cm in standard length) looks quite different from the adult. The body is more compressed and angular, with 10-13 prominent, flattened, bladelike, spiny scutes projecting laterally from the surface of each side of the body. Each scute is an outgrowth from a scale whose basal part is divided, overlapping both sides of the one behind. On the base of the larger scutes are retrorse spinules. The scutes become smaller as the fish grows, and they eventually shrink to nothing as the fish transforms to an adult at about 10-12 in (25-30 cm). Adults are silvery in color, with bronze reflections. Juveniles are silvery, with irregular black blotches on the body, black spots on the tail fin, and 5 black bars on anal fin.
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