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Author: Jordan and Snyder, 1903

Field Marks:
Two dorsal fins with ungrooved large spines, first dorsal spine origin in front of pectoral rear tips, first dorsal spine much shorter than fin base, first dorsal low and less than 2/3 as high as long, moderately long rounded-parabolic 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 stout. Snout parabolic-rounded, broad, and moderately long, diagonal distance from snout tip to excurrent aperture of nostril greater than that from exeurrent aperture to upper labial furrow, preoral snout about 1.1 to 1.4 times mouth width, preorbital snout less than twice eye length; eyes nearer the snout tip than the first gill slits; nostrils closer to snout tip than mouth; anterior nasal flap with small oosterior secondarv lobe. considerablv narrower at base than distance from its base to inner cornerof nostril. First dorsal spine moderately long, much less than fin base and with tip falling well below apex of fin; second spine long, about as high as fin, and less than 6% of total length; first dorsal fin more anteriorly situated, with fin origin about over pectoral insertions and spine origin over pectoral inner margins and in front of their rear tips; first dorsal moderately high, height less than 2/3 its length from origin to rear tip; second dorsal markedly smaller than first, with height usually less than 5% of total length. Precaudal pits strong; pectoral fins broad and semifalcate, posterior margins slightly concave, rear tips narrowly rounded; pelvic midbases closer to second dorsal base than first; caudal fin narrow-lobed and long, with long ventral lobe and strongly notchedpostventral margin. Precaudal pits strong. Lateral trunk denticles tricuspidate and with strongly scalloped posterior borders in adults. Colour: no white spots present on sides of body, fins with white edges but without conspicuous dark markings. Size moderate, up to about 1 m.

Geographical Distribution:
Western North Pacific: Japan, the Koreas, China, probably Taiwan Island and Viet Nam, also seamounts in the North Pacific. Western South Pacific: Possibly New Zealand. Central Pacific: Hawaiian Islands (Chen, Taniuchi and Nose, 1979). There are dogfishes very similar to this species and possibly identical off Tasmania and Australia, the Philippines, South Africa, and the eastern and western Atlantic, that are apparently not conspecific with S. blainvillei. Records of S. blainvillei or S. fernandinus from the western Indian Ocean (Mozambique, Madagascar, Tanzania, and India), New Caledonia, and the eastern Pacific off northern Chile may also involve S. mitsukurii

Habitat and Biology:
A common dogfish of warm-temperate and tropical seas, found near or on the bottom on the continental and insular shelves and upper slopes at depths of 180 to 300 m in the western North Pacific; the Hawaiian Islands at 165 to 518 m; and New Zealand at 4 to 55 m. Very similar and perhaps conspecific dogfishes occur at depth of 432 m off the Philippines, at 50 to 740 m off South Africa, at 183 to 549 m off southern Australia and Tasmania, at 190 m off northern Chile, and 330 to 394 in the Gulf of Mexico.

Ovoviviparous. Off the east coast of South Africa this species or a close relative has 4 to 9 young per litter, with most births in the autumn, a possible gestation period of up to two years, and sexual segregation of females in the southern part of its range. Off South Africa this shark or a cognate feeds mostly on bony fishes (57%), cephalopods (31%) and crustaceans (10%).

Size:
Maximum total length 110 cm, females mature at 72 cm and males betwee 65 and 89 cm; size at birth about 22 to 26 cm.

Interest to Fisheries:
Apparently common in the western North Pacific, and taken in fisheries there, but details unknown.

Remarks:
The arrangement of this species follows the recent revision of western North Pacific blainvillei- like dogfishes by Chen, Taniuchi and Nose (1979). I have examined the holotype of S. philippinus Smith and Radcliffe, 1912 and found that it agrees with S. mitsukurii in most details (specimen is USNM 70257, 32.5 cm immature male, from off Sombrero Island, Philippine Islands in 432 m depth). I include it as a possible synonym of S. mitsukurii (along with the replacement name S. montalbani), but note that Chen, Taniuchi and Nose (1979) regarded the species as being distinct from S. mitsukurii without mentioning details. They apparently did not examine the holotype of S. philippinus.

Type material:
Holotype: Stanford University Natural History Museum, SU-12793, ca. 724 mm adult female. Type Locality: Misaki, Japan.

Shortspine spurdog (Squalus mitsukurii)