Author: Smith, 1957
A fairly large, usually white-spotted Mustelus with a relatively broad internarial space, buccopharyngeal denticles covering almost entire oral cavity, unfringed dorsal fins, relatively large pectoral and pelvic fins, and 74 to 88 precaudal centra. It is the only white-spotted smooth-hound in southern African waters.
Body fairly slender. Head short, prepectoral length 17 to 21% of total length; snout moderately long and bluntly angular in lateral view, preoral snout 6 to 7.4% of total length, preorbital snout 6.1 to 7.5% of total length; internarial space broad, 2.4 to 3% of total length; eyes fairly large, eye length 1.7 to 2.4 times in preorbital snout and 2.8 to 4% of total length; interorbital space moderately narrow, 3.7 to 4.7% of total length; mouth short, subequal to eye length and 2.6 to 3.3% of total length; upper labial furrows longer than lowers and 1.7 to 2.5% of total length; teeth molariform and asymmetric, with cusp reduced to a low point, cusplets absent except in very young sharks; buccopharyngeal denticles covering almost entire palate and floor of mouth. Interdorsal space 18 to 23% of total length; trailing edges of dorsal fins denticulate, without bare ceratotrichia; first dorsal broadly triangular, with posteroventrally sloping posterior margin, its midbase closer to pectoral bases than pelvics; pectoral fins large, length of anterior margins 14 to 18% of total length, width of posterior margin 12 to 16% of total length; pelvic anterior margins 6.4 to 9.3% of total length; anal height 3.2 to 4.1% of total length; anal-caudal space greater than second dorsal height, and 7 to 8.8% of total length; ventral caudal lobe somewhat expanded and sometimes semi falcate in adults. Crowns of lateral trunk denticles lanceolate or weakly tricuspidate, with longitudinal ridges confined to their anterior halves or extending their entire length. Skeleton not hypercalcified in adults; palatoquadrates not subdivided; monospondylous precaudal centra 36 to 40, diplospondylous precaudal centra 43 to 52, precaudal centra 74 to 88. Colour uniform grey or grey-brown above, light below, usually with numerous small white spots but no dark spots or dark bars. Development ovoviviparous. Size large, adults 76 to 120 cm.
Eastern South Atlantic and southwestern Indian Ocean: Namibia, South Africa and extreme southern Mozambique.
Habitat and Biology:
A common inshore and offshore temperate-water shark of the continental shelf and upper slope, on or near bottom at depths from the intertidal region down at least to 360 m depths. Prefers sand and gravel bottoms.
Ovoviviparous, without a yolk-sac placenta; number of young 3 to 8 per litter. Eats crabs and probably other invertebrates.
Maximum about 120 cm; adults females 79 to 102 cm, adult males 76 to 88 cm.
Interest to Fisheries:
Limited, often taken by sports anglers and by commercial bottom trawlers, but usually discarded although excellent eating. Some may be utilized in a local fishery that processes sharks for 'biltong', dried shark meat or jerky, for human consumption.
In its range, this species is primarily sympatric with the unspotted or dark-spotted Mustelus mustelus, which differs in its shorter labial furrows that are only slightly longer than the lowers, slightly smaller pectoral fins, less extensive buccopharyngeal denticles, more falcate fins, and less numerous monospondylous precaudal centra. The unspotted, more tropical M. mosis of the western Indian Ocean overlaps its northeastern range of Natal, South Africa, and differs in having smaller upper labial furrows subequal to the lowers, smaller pectorals, less extensive buccopharyngeal denticles, and a strongly hypercalcified skeleton. Of closely similar, Eastern Hemisphere white-spotted species M. manazo differs in being smaller and in having smaller paired fins; M. lenticulatus and M. antarcticus have less extensive buccopharyngeal denticles; and M. asterias has smaller paired fins, a narrower internarial, and somewhat more vertebrae.
Holotype: J.L.B. Smith Institute of Ichthyology, Grahamstown, South Africa, RUSI 24, 990 mm female (head, tail, and fins preserved). Type Locality: Knysna estuary mouth, South Africa, in shallow water.