Author: Cope, 1877
A white-spotted thickset Mustelus with a bluntly angular, short snoutS short caudal peduncle, and broadly rounded, acuspidate teeth.
Body stocky. Head fairly short, prepectoral length 18 to 23% of total length; snout moderately long and bluntly angular in lateral view, preoral snout 6 to 7.9% of total length, preorbital snout 6.9 to 9% of total length; internarial space broad, 2.4 to 3% of total length; eyes fairly small, eye length 2.2 to 3.9 times in preorbital snout and 1.7 to 3.5% of total length; interorbital space moderately broad, 4.5 to 5.6% of total length; mouth short, subequal to eye length and 2.5 to 3.5% of total length; upper labial furrows usually slightly longer than lowers and 2.2 to 2.9% of total length; teeth molariform and symmetrical, with cusp absent and crown broadly rounded; buccopharyngeal denticles covering almost all of palate and mouth floor. Interdorsal space 17 to 22% of total length; trailing edges of dorsal fins denticulate, without bare ceratotrichia; pectoral fins fairly large, anterior margin length 12 to 17% of total length, width of posterior margins 8.5 to 14% of total length; pelvic fins fairly large, anterior margin length 7.6 to 9.7% of total length; anal height 2.8 to 3.9% of total length; anal caudal space somewhat less than second dorsal height, and 5.7 to 7.5% of total length; ventral caudal lobe more or less falcatein adults. Crowns of lateral trunk denticles lanceolate, with longitudinal ridges, when present, extending only on their anterior halves. Skeleton not hypercalcified in adults; palatine processes of palatoquadrates subdivided at symphysis with a short separate medial segment on each side; monospondylous precaudal centra 30 to 41, diplospondylous precaudal centra 28 to 52, precaudal centra 71 to 91. Colour uniform grey or grey-brown above, light below, with numerous white spots but no dark spots; dark bars present in young below 35 cm. Development ovoviviparous. Size large, adults 65 to 130 cm.
Eastern South Pacific: Galapagos Islands, Peru, Chile, Juan Fernandez Island. Western South Atlantic: Argentina.
Habitat and Biology:
A temperate bottom-dwelling shark of continental and insular shelves, found inshore and offshore, at depths of 16 to 50 m. Ovoviviparous, number of young 7 per litter.
Maximum recorded 130 cm, males maturing between 65 and 76 cm, females maturing between 86 and 90 cm; size at birth about 30 cm.
Interest to Fisheries:
Regularly taken in its area along with other species of "tollo" (Mustelus), for human consumption (N. Chirichigno, pers. comm.).
Bigelow and Schroeder (1948) summarized nominal South Atlantic, Argentinian records for this species, which may possibly be based on other species, perhaps M. schmitti or M. fasciatus. The rounded teeth of this species are shared by M. fasciatus, but other species of Mustelus have weakly to strongly cuspidate teeth.
Holotype: Academy ofNatural Sciences of Philadelphia, ANSP 21104, 300 mm. Type Locality: Peru.