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Author: Merrett, 1973

Diagnostic Features:
Body stout. Snout roundedparabolic, broad, and moderately long, diagonal distance from snout tip to excurrent aperture of nostril slightly less than that from excurrent aperture to upper labial furrow, preoral snout about 0.8 to 1.1 times mouth width, preorbital snout less than twice eye length; eyes slightly nearer snout tip than first gill slits: nostrils nearer snout tip than mouth; anterior nasal flap with very large posterior secondary lobe that is usually as broad as distance from its base to inner end of nostrils. First dorsal spine usually moderately long, about half fin base and with tip falling somehwat below apex of fin or reaching it; second long, about as high as fin, and over 6% of total length; first dorsal fin more posteriorly situated, with fin origin opposite or well behind pectoral rear tips and spine origin well behind tips; first dorsal fairly low, height about half length from origin to rear tip; second dorsal about as large as first, with height over 5% of total length; pectoral fins broad and triangular, posterior margins nearly straight, rear tips broadly rounded; pelvic midbases much closer to second dorsal base than first; caudal fin rather broad-lobed and short, with short ventral lobe and moderately concave postventral margin. Precaudal pits weak or absent. Lateral trunk denticles unusually large and tricuspidate and with moderately scalloped posterior borders in adults. Colour dark grey or brown above, lighter below, without white spots on sides of body but with dorsal fins, caudal. and Dectorals with conspicuous white edges. Size large,up to nearly 1.2 m.

Geographical Distribution:
Western North Atlantic: Northern Gulf of Mexico. Western Indian Ocean: South Africa, southern Mozambique, Aldabra Island group. Central Pacific: Hawaiian Islands.

Habitat and Biology:
A little-known but very distinctive spiny dogfish of the upper continental and insular slopes, on or near the bottom, at depths of 214 to 600 m. Ovoviviparous, with large litters (for a spiny dogfish) of 21 to 22 young. Eats bony fish and squid.

Size:
Maximum total length 118 cm; adult males 85 to 90 cm and adult females 89 to 118 cm; size at birth about 25 to 28 cm.

Interest to Fisheries:
None at present.

Remarks:
Gulf of Mexico and Hawaiian records of the species from S. Springer (pers.comm.).

Type material:
Holotype: British Museum (Natural History), BMNH 1972.10.10.2, 850 mm adult male. Type Locality: Indian Ocean, off Aldabra Island, 09°27'5, 46°23.5'E, 219 m depth.

Roughskin spurdog (Squalus asper)