Author: Gill, 1862
Field Marks:
Small sharks, superficially similar to members of the family Scyliorhinidae in their slender form, catlike eyes with subocular pockets, first dorsal origin behind pelvic bases, and fin proportions, but differing in having their mouths entirely in front of eyes and in having narrow nasoral grooves, circumnarial grooves and folds around the nostrils, and medial barbels not derived from the anterior nasal flaps. Their mouth and nostril structures, two spineless dorsal fins and an anal fin, anal fin origin well ahead of second dorsal origin, and minute spiracles distinguish them from other sharks.
Diagnostic Features:
Body cylindrical or slightly depressed, without ridges on sides. Head narrow and slightly flattened, without lateral flaps of skin, snout broadly rounded to slightly pointed; eyes dorsolaterally situated on head, with subocular pockets; spiracles minute, much smaller than eyes and not 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 arched, without a symphyseal groove on chin; teeth no strongly differentiated in jaws, with a medial cusp, lateral cusplets and relatively strong labial root lobes; tooth rows 27 to 54/25 to 49. Dorsal fins equalsized, first dorsal with origin and insertion well behind the pelvic bases; 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 greater than anal fin; anal fin somewhat smaller than second dorsal, with its origin well ahead of second dorsal origin; anal fin with broad base and angular apex, separated by a space greater than its base length from lower caudal origin; caudal fin with its upper lobe not elevated above the body axis, less than a quarter as long as the entire shark, with a strong terminal lobe and subterminal notch but no ventral lobe. Caudal peduncle without lateral keels or precaudal pits. Supraorbital crests absent from cranium. Valvular intestine of spiral type. Colour pattern of dark and light spots and saddle markings, in some species also a dark collar around gills.
Habitat, Distribution and Biology:
These are little-known, rare to common, harmless bottom sharks of often deepish temperate and tropical, continental waters of the western Pacific, occurring from close inshore to at least 183 m offshore. One genus (Parascyllium) is confined to Australian waters while the second (Cirrhoscyllium) occurs in the China Sea north to Japan and Taiwan Island. They are found on muddy, sandy or rocky bottom, and apparently can change colour somewhat to match the bottom type. All species are small, less than a metre long when mature. At least some of the species are ovoviviparous, depositing eggs in elongated, flattened egg cases on the bottom. Food is little known, but probably include small fishes, crustaceans, and other bottom invertebrates.
Interest to Fisheries:
Several species are taken in bottom trawls, but utilization is probably minimal.
Remarks:
Applegate (1974) proposed a separate family for the genus Cirrhoscyllium, but external and anatomical studies by the writer strongly suggest that this genus is closely related to Parascyllium although readily distinguishable from it, and that both genera are referable to a single family. These sharks are remote from other orectoloboids and are distinguishable from them by their teeth, with strong labial rooth lobes (variably reduced in other orectoloboids) and low basal ledges (expanded in most other orectoloboids); well-arched mouths; anal fin origin well anterior to second dorsal origin; cranium greatly reduced, with no supraorbital crests, suborbital shelves narrow and reduced, anterior fontanelle extending rearward to between endolymphatic foramina and nearly reaching foramen magnum, huge fenestrae on dorsal and posterolateral surfaces of the nasal capsules; an extraordinary suite of highly specialized head muscles that are unique to these sharks, including the anterodorsal palbebral depressor that closes the upper eyelids, the dorsal rostronuchal and ethmonuchal muscles between nape and snout, and the ethmomandibular muscle between jaws and snout; vertebral central with simple wedge-shaped intermedialia but no radii; and spiral intestinal valves (a ring valve, or quasi-ring valve in other orectoloboids). Clasper morphology is unknown for Cirrhoscyllium, but Parascyllium has highly specialized claspers with a unique, medial, fingerlike, spurbearing lobe supported by the dorsal terminal cartilage as well as a row of unique clasper hooks on the ventral terminal cartilage.
Applegate (1974) placed the two parascylliid genera in a separate suborder of the Orectolobiformes, emphasizing their distinctiveness; in cladistic terms, the Parascylliidae is the quasi-primitive sister group of all other orectoloboids.