Author: Gill, 1862
Field Marks:
Small, slender sharks with nasoral grooves, perinasal grooves, short barbels, small transverse mouths in front of eyes, dorsolateral eyes, large spiracles below eyes, no lateral skin flaps on head, two spineless dorsal fins, the second dorsal origin well ahead of the anal origin, a long, low keel-like rounded anal fin separated from the lower caudal origin by a narrow notch, and a long precaudal tail much greater than the head and body length.
Diagnostic Features:
Body cylindrical or slightly depressed, with or without ridges on sides. Head narrow to moderately broad and cylindrical to somewhat flattened, without lateral flaps of skin, snout broadly rounded or slightly pointed; eyes dorsolaterally situated on head, without subocular pockets; spiracles very large, subequal in size to eyes and somewhat below them; gill slits small, fifth overlapping fourth; internal gill slits without filter screens; nostrils with short, pointed barbels and distinct circumnarial folds and grooves around outer edges of incurrent apertures; mouth small, subterminal on head, and nearly transverse, without a symphyseal groove on chin; teeth not strongly differentiated in jaws, with a medial cusp, lateral cusplets present or not, and weak labial root lobes; tooth rows 26 to 35/21 to 32. Caudal peduncle without lateral keels or precaudal pits. Dorsal fins equal-sized, first dorsal with origin varying from over the pelvic bases to well behind them and insertion well behind the pelvic rear tips; pectoral fins small, broad and rounded, as large as pelvic fins or slightly larger, with fin radials not expanded into fin web; pelvic fins about as large as dorsals but slightly larger than anal fin; anal fin somewhat smaller than second dorsal, with its origin behind second dorsal insertion; anal fin with broad base and broadly rounded, keel-like apex, separated by a narrow notch much less than base length from lower caudal origin; caudal fin with its upper lobe hardly elevated above the body axis, less than a fifth as long as the entire shark, with a strong terminal lobe and subterminal notch but no ventral lobe. Supraorbital crests present on cranium, not laterally expanded. Valvular intestine of ring type. Colour pattern of dark saddles and dark or light spots present, or colour plain.
Habitat, Distribution and Biology:
These are common, small, harmless, inshore bottom sharks of continental waters of the tropical western Pacific, ranging from Madagascar in the west to Japan, the Philippines, and the Australian region in the east. One genus (Hemiscyllium) is confined to Australia and New Guinea, but the second (Chiloscyllium) is wide-ranging. They commonly occur in the intertidal, in tidepools on rocky or coral reefs close inshore, sometimes in water sufficient only to cover them. Their slender bodies and strong, muscular, leg-like paired fins are ideal for clambering on reefs and in crevices. These sharks are small, less than 1 m maximum length. At least some of the species are oviparous, depositing eggs on the bottom in oval egg cases. Food of these sharks is little known, but probably includes small bottom fishes and invertebrates. Several of the species are very hardy and can live over a decade in captivity and even reproduce there.
Interest to Fisheries:
Hemiscyllium species are little utilized for fisheries, but Chiloscyllium species are commonly caught in smallscale artisanal fisheries and by bottom trawlers in the western Pacific and eastern central Indian Ocean.
Remarks:
The arrangement of this family follows Garman (1913), Fowler (1941) and Whitley (1967).
Dingerkus and DeFino (1983) present a comprehensive revision of this family, which must be briefly dealt with here. The species listed in the present account are recognized by these authors with the exception of Chiloscyllium caerulopunctatum, which is synonymized with C. plagiosum, and C. arabicum, which was apparently overlooked. They recognize an Indonesian species, C. hasselti Bleeker, 1852, formerly synonymized with C. griseum, and describe two new species, C. burmensis from Burma and C. confusum from the "Gulf" east to India. C. hasselti and C. burmensis appear to be valid, while C. confusum seems to be a junior synonym of C. arabicum.