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Author: Ishikawa, 1908

Field Marks:
Two dorsal fins with ungrooved, large spines, first dorsal fin height less than 2/3 of its length from origin to base. First dorsal spine origin over pectoral inner margins, long, very angular prenarial snout with distance from tip to inner nostril greater than distance from nostril to upper labial furrow, tricuspidate lateral denticles, no white spots, oblique-cusped cutting teeth in both jaws, no subterminal notch on caudal fin, no anal fin, and upper precaudal pit and lateral keels on caudal peduncle.

Diagnostic Features:
Body fairly slender. Snout angular, broad-based but narrow-tipped, and very long, diagonal distance from snout tip to excurrent aperture of nostril greater than that from excurrent aperture to upper labial furrow, preoral snout about 1.5 to 1.9 times mouth width, preorbital snout at least twice eye length; eyes closer to first gill slits than snout tip; nostrils closer to mouth than snout tip; anterior nasal flap with posterior secondary lobe small and considerably narrower at base than distance from its base to inner corner of nostril. First dorsal spine moderately long, much less than fin base and with tip falling well below apex of fin; second spine long, slightly lower than fin, and usually less than 6% of total length; first dorsal fin anteriorly situated, with fin origin over pectoral inner margins and spine origin over or slightly behind pectoral rear tips; first dorsal fairly low, height slightly less than 2/3 of its length from origin to rear tip; second dorsal markedly smaller than first, with height less than 5% of total length; pectoral fins broad and sernifalcate, posterior margins slightly concave, rear tips narrowly rounded; pelvic midbases about equidistant between first and second dorsal bases; caudal fin narrow-lobed and long, with long ventral lobe and strongly notched postventral margin. Precaudal pits strong. Lateral trunk denticles tricuspidate and with weakly scalloped posterior borders in adults. Colour: no white spots present on sides of body, dorsal fins with white edges, caudal without dark markings. Size moderate, up to slightly less than 1 m.

Geographical Distribution:
Western North Pacific: Southeastern Japan and East China Sea, including the Republic of Korea and the Philippines.

Habitatand Biology:
A common but little known temperate and tropical dogfish of the outer continental and insular shelves and uppermost slopes at 150 to 300 m depth, presumably on or near bottom.

Size:
Maximum total length 91 cm, females mature at 79 cm.

Interest to Fisheries:
Apparently common in its range and taken in fisheries off Japan, but details not available.

Remarks:
This species is usually synonymized with S. mitsukurii or S. fernandinus, but is recognized here following Chen, Taniuchi and Nose (1979).

Type material:
Holotype: Types not named and apparenity not extant (see Chen, Taniuchi and Nose, 1979). Type Locality: Ishikawa (1908) mentioned three specimens, 2 from Tokyo Market and apparently from the Sagami Sea, and one from Kagoshima, Japan, on which he based his description of S. japonicus and deposited in the National Science Museum, Japan.

Japanese spurdog (Squalus japonicus)