Stromateoids are moderate-sized fishes up to 47.2 in (1.2 m) in length, generally with round and somewhat large eyes (with associated adipose tissue in ariommas), small mouths, forked caudal fins (with 15 branched rays), and elongated dorsal fins that may be continuous or subdivided. The body is slender to deep, and is either compressed laterally or rounded in cross-section. The dorsal fins have spines (weak in some species); an anal fin with one to three spines; the dorsal and anal fins generally terminate at the same level; pelvic fins are absent in adults of some species (e.g., butterfishes, although the pelvic bones are present); pelvic fins are small in others, and very large in the man-of-war fish (Nomeus gronovii). The jaw teeth are small, usually arranged in a single series; the nostrils are double; a lateral line is present. The gill rakers range from 10-20 on the first gill arch. Scales are usually cycloid. Coloration may vary from silvery to dark brown in adults, but is usually mottled in juveniles. Some species have more elaborate color patterns, with blotches and bands.
Stromateoids, with the exception of the Amarsipidae, are unique in having a specialized pharyngeal organ (the pharyn-geal sac) just anterior to the esophagus and following the last gill arch, which is specialized for further breaking down food items. The pharyngeal sacs are coated internally by small projections (papillae) that contain minute "teeth"; the structure and arrangement of the papillae vary significantly among species. All stromateoids share a specific configuration of the internal caudal fin skeleton.
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