Squatina nebulosa (Regan, 1906)

Jonathan H. Walsh & David A. Ebert, 2007, A review of the systematics of western North Pacific angel sharks, genus Squatina, with redescriptions of Squatina formosa, S. japonica, and S. nebulosa (Chondrichthyes: Squatiniformes, Squatinidae)., Zootaxa 1551, pp. 31-47 : 42-44

Squatina nebulosa (Regan, 1906)

Squatina nebulosa, Regan 1906 : 439, valid, holotype (unique): BMNH 1862.11.1.89 (Eschmeyer, 2005). Figure 5.

Common name. Clouded angel shark

Diagnosis. A squatinid with the following distinctive characters: upper lip arch half-oval in shape (3.1- 4.7% TL in width, 0.7-1.5% TL in height), generally shorter in height and width than S. formosa , greater in height than S. japonica ; pelvics with broad lateral expansion, anterior margin rapidly extending to lateral extreme of pelvic fin then gradually tapering off towards the body posterior; posterior tip of pectoral fin more angular, angle of tip not much more than 120°, pelvic fin tips reach first dorsal base; dorsal fins angular in shape with a straight anterior margin, dorsal bases are approximately equal; caudal fin very angular dorsally with a straight posterior ventral margin.

Description. Dorsal surface, except for posterior of caudal fin, covered with denticles of moderate roughness. Ventral surface smooth except for narrow bands of denticles on the pectoral and pelvic fin anterior margins.

Head rounded, slightly squat, length about 0.2 times total length, greatest width occurring just anterior of gill openings. Interspersed moderately rough tubercles above mouth and eye crests. Eyes almond-shaped, widely set, interorbital space 8.1 (7.9-8.5). Eye-spiracle space short. Spiracles crescent shaped without large papillae. Interspiracle space 6.7 (7.5-7.8) less than interorbital space. Center of upper lip anteriorly exposed forming an upper lip arch semi-oval in shape, extending dorsally nearly one half of upper jaw space, upper lip arch height 1.0 (0.7-1.5), upper lip arch width 4.7 (3.1-3.8). Dermal folds along exterior of head with one to two small lobes at corners of mouth extending ventrally. Nostrils large and slightly protruding. Distinct nasal flaps protruding from dermal folds above mouth with two barbels protruding from each flap. Inner nasal barbel rod-like with a spatulate tip, with inner basal portion containing little if any fringe. Outer nasal barbel narrow. Labial furrows conspicuous, roughly equal in length, extending from corners of mouth medially. Upper labial furrow partially covered with dermal folds. Mouth length about 0.2 times as long as mouth width. Dentition consists of small, dagger-like teeth, conical without cusplets on broad base, arranged longitudinally in three orderly rows, tooth count per row 10-10 / 10-10.

Pectoral fins large, angular overall in shape, originating just behind gills. Anterior margin, approximately 0.8 times as long as pectoral fin length, straight extending to broadly rounded lateral apex. Angle of lateral apex approximately more than 120 °. Margin from lateral apex to most posterior lobe slightly concave. Pectoral inner margin slightly convex.

Pelvic fins, originating anterior to pectoral fin free rear tip, somewhat triangular with rounded fin tips. Pelvic fin length approximately 0.7 times as long as pectoral fin length. Pelvic fin base about 1.3 times longer than pectoral fin base. Anterior margin, about half as long as pelvic fin length, extending at roughly a 45 ° angle from trunk and loops outward to rounded lateral apex. Pelvic girdle width (25.3-34.8) broad, greater than 1.4 times head length. Posterior of pelvic fin straight to posterior fin tip, which reaches origin of first dorsal. Pelvic inner margin, about half as long as pelvic fin length, straight to slightly concave.

Dorsal fins triangular, with denticles extending over the whole of the fins. First dorsal slightly larger than second in some specimens. Interdorsal space approximately 0.8 times dorsal caudal finspace. Anterior margin of dorsals straight, nearly equidistant among dorsals. First and second dorsal bases nearly equal in most specimens, first dorsal base 5.5 (3.5-4.1), second dorsal base 4.9 (3.4-4.0). Apices of dorsals angular. Posterior margins, about 0.6 times length of anterior margins, straight. Inner margins of dorsals, approximately 0.4 times as long as anterior margins, slightly convex.

Caudal peduncle compressed dorso-ventrally with lateral longitudinal ridges, tapering posteriorly.

Caudal fin angular throughout, especially dorsally. Caudal dorsal margin approximately 0.7 times preventral caudal fin margin. Subterminal caudal fin margin, about 0.4 times as long as upper caudal postventral margin, straight. Caudal lower postventral margin, approximately 0.8 times as long as upper caudal postventral margin, convex.

Total vertebrae 138-139; total precaudal vertebrae 108; monospyndolous vertebrae 49; diplospondylous vertebrae 59; caudal vertebrae 30-31.

Coloration. Dorsal surface of specimens prior to preservation dark brown throughout with many black and white spots of varying sizes. Black spots laterally at origins of dorsals. Ventral surface pale white with some black mottling, pectoral and pelvic fin ventral margins with denticles colored similar to dorsal. Dorsal color after preservation fades to a lighter brown, white spots, especially white ones, can become indistinct with preservation.

Distribution. Endemic to WNP including southern Japanese waters, central and eastern north China Sea, western Taiwan Straits (Shuyuan, 1994), and waters surrounding northern Taiwan (Compagno et al., 2005a).

Etymology. Naming is in reference to the dorsal coloration pattern of the species, which can have a cloudy appearance.

Remarks. Examination of S. nebulosa specimens suggests four distinct characters: an angular caudal fin, angular dorsal fins, a pelvic girdle width greater than 1.4 times the head length (when both measures are standardized by total length), and a upper lip arch that is semi-oval in shape due to an upper lip arch height less than 1.5% TL. Study of photographs of the S. nebulosa holotype (BMNH 1862.11.1.89, Fig. 5C, 6) provided confirmation of these distinct characters belonging to this species.

The paratypes for S. formosa (NTUM 01327(x2) and NTUM 01328) also possess these distinct characters. Therefore, it is our contention that this represents strong evidence that the paratypes for S. formosa are in fact true S. nebulosa .

Previous work (Lindberg & Legeza, 1967) indicates that in S. nebulosa interspiracle distance is less than interorbital distance; a finding consistent with our observations.

Material Examined. Comparative material: DAE 882105, immature female, Tahsi, Taiwan, May 1988, collected by David A. Ebert ; DAE 052305-1, immature male, Tahsi, Taiwan, May 2005, collected by David A. Ebert ; DAE 052505, immature male, May 2005, collected by David A. Ebert ; HUMZ 149422, immature female, caught in trawl net in Okinawa Trough (25° 37.28’N, 126° 05.35’E to 25° 38.12’N, 126° 07.83’E), 02-Aug-1994 ; HUMZ 149423, immature male, caught in trawl net in Okinawa Trough (25° 37.28’N, 126° 05.35’E to 25° 38.12’N, 126° 07.83’E), Japan, 02-Aug-1994 .