As with other Percoidei fishes, these fishes are characterized by the presence of spines in the dorsal, pelvic, and anal fins; the presence of two dorsal fins but no adipose fin; the abdominal placement of pelvic fins; pectoral fins that are placed laterally and oriented vertically; the presence of 17 or less principal rays in the caudal fin; and, usually, ctenoid scales (some species possess cycloid scales). These fishes are further characterized by a maxilla that is excluded from the gape of the jaw, a gas bladder that is physoclistous (lacking a connection between the gas bladder and the gut), and bone that is acellu-lar. They also lack four specific bone types: the orbitosphe-noid (within the orbital region of the skull), the mesocoracoid (within the pectoral girdle; this bone helps to position the pectoral fin obliquely rather than vertically, as in the percoids), the epileural (riblike intermuscular bones extending below the vertebral column), and the epicentral (primitively ligamen-tous, riblike intermuscular bones). Body shapes are quite divergent, and range from deep-bodied and highly compressed (Kyphosidae, Drepaneidae, Monodactylidae, Pentacerotidae, Chaetodontidae, Pomacanthidae, and Cheilodactylidae) to elongated (Mullidae) forms. Similarly, there is considerable
variation in the ecomorphology of the head, jaws, or other structures, both between and within families. Some families, such as the Chaetodontidae, Pomacanthidae, and Cirrhitidae, include many species with brightly colored or highly conspicuous color patterns. Other families (Nandidae) are noted for the cryptic coloration of many species.
Goatfishes are characterized by pairs of long, chemosen-sory barbels under the lower jaw, a terminal mouth, and the presence of large ctenoid scales. Goatfish larvae are laterally compressed and moderate in depth or elongate. The barbels begin to form at about a length of 0.3—0.35 in (0.8-0.9 cm). Archerfishes have moderately compressed bodies, a pointed head, a dorsal that originates well back towards the caudal fin, and a grooved palate that can direct a stream of water into the air. Their larvae are moderate in depth initially, but become deeper, compressed, and heavily pigmented with age. Galjoens have deep bodies, small ctenoid scales (even on the fins), and a scaleless snout. Sea chubs have a small head with a terminal mouth, a deep and moderately compressed body, a dorsal fin that is continuous, and a caudal fin that is either emarginate (notched) or forked. Their larvae are initially elongate, but become moderate in depth with age, with moderate-to-heavy pigmentation. There is some variation between subfamilies. The jutjaw has an oval-shaped, compressed body, small ctenoid scales, and a large mouth with a projecting lower jaw. Sicklefishes have strongly compressed, oval-shaped bodies covered with cycloid scales and protusile mouths. Monos have deep, highly compressed bodies that are covered with small deciduous scales. Pelvic fins are present in juveniles, but become rudimentary or absent in adults. Their larvae are specialized, having head spination that is moderately developed and elongate pelvic fins that form rather early.
The butterflyfishes have deep, highly compressed bodies; small protractile mouths; somewhat small ctenoid scales; a single dorsal fin that is continuous; and a caudal fin that is rounded or slightly emarginate. The post-larvae have a distinctive tholichthys stage, denoted by the presence of bony plates and protruding spines on the head. Angelfishes also have deep, compressed bodies, along with small ctenoid scales, small mouths, and a single dorsal fin that is un-notched. Characters that differentiate angelfishes from the butterflyfishes are a single prominent spine located at the corner of the preopercle; smaller spines on the preopercle, interopercle, and preorbital; and the absence of a tholichthys postlarval stage. The oldwife, as an adult, has remarkably large dorsal, pelvic, and anal fins, as well as small ctenoid scales, and a deep, compressed body. Sharp spines are present on the head, anal fin, and dorsal fin; the dorsal spines contain poison and thus the oldwife must be handled with care. Larvae are elongate to moderately long, and are heavily pigmented.
Boarfishes and armorheads resemble the adult oldwife. They have deep, moderately to strongly compressed bodies, exposed head bones that form rough, striated plates, and may have elongated mouths and fin rays. Juveniles may have tall dorsal fins and elongated anal and pelvic fins, but these are reduced as adults. Some species have poisonous spines and should be handled with care. Their larvae are denoted by elongate pelvic fins and extensive, well-developed spination on the head. Leaffishes possess large heads and mouths (the mouth is protactile), continuous dorsal fins, and rounded caudal fins. Knifejaws (Oplegnathidae) have oblong, moderately compressed bodies, tiny ctenoid scales, a single dorsal fin, and a parrotlike beak reminiscent of that on the distantly related par-rotfishes (Scaridae). Knifejaw larvae lack subopercular or in-teropercular spines and are lightly pigmented. Hawkfishes resemble small groupers and their allies (Serranidae) and are characterized by the presence of filaments arranged in small tufts on the tips of the dorsal fin spines and by lower pectoral fin rays that are thickened. Members of the genus Paracirrhites, especially P. arcatus, P. hemistictus, and P. forsteri, are polychromatic. Two fixed color morphs occur in the former two species, while the latter exhibits two fixed color patterns in juveniles and a wide range of patterns that have no apparent relationship to sex, adult body size, or geographic locality. However, geographical color variation has been reported for the wide-ranging Cirrhitus pinnulatus. Hawkfish larvae have a pigmented chip barbel that disappears with age, cirri on the tips of the dorsal fin spine membrane, and serrations on the preopercle.
Kelpfishes are grouper or hawkfish-like in appearance, with cycloid scales that are moderately large, large pectoral fins, filaments on the tips of dorsal fins, and tufts of filaments on the dorsal spines of some species. Larvae are elongate to moderate in length, lack head spines, have heavy pigmentation in the postflexion stage, and are unspecialized. Sea carps have robust, elongate bodies, small cycloid scales, and pectoral fins with thickened lower rays positioned well forward under the gill covers. Their larvae are long to very elongate, lacking in head spines, heavily pigmented in the postflexion stage, and rather unspecialized. Many morwongs have elongated pectoral rays, forked caudal fins, an elevated dorsal fin, and large rubbery lips. A humplike head and back is present in a number of species. The postlarval stage of morwongs is silvery in color, deep-bodied, and very thin. This stage is retained in most species until they reach 17.7-23.6 in (45-60 cm) in total length. Although somewhat similar in shape to morwongs, the trumpeters have bodies that are elongate and compressed, with small pectoral fins, dorsal fins that are deeply notched, and a protruding mouth. Their postlarval stage resembles that of the morwongs.
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