Squatina formosa (Shen & Ting, 1972)

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 : 35-38

Squatina formosa (Shen & Ting, 1972)

Squatina formosa, Shen & Ting 1972 : 23, Figure 4, valid, holotype: NTT7213130. Figure 2.

Common name. Taiwan angelshark.

Diagnosis. A squatinid with the following distinctive characters: upper lip arch semi-circular, height greater than other WNP squatinids (3.8-5.1% in width, 1.4-2.1% TL in height); pectoral fins broadly rounded, especially posterior free tip; pelvic girdle moderately broad, pelvic anterior margin slightly curved, angle of lateral apex considerably more obtuse than 120°, pelvic fin tips reaching first dorsal origin; dorsal fins lobe-like with slightly rounded anterior margin, first dorsal fin base slightly larger than second dorsal base; caudal fin lobed, especially dorsally, with a curvilinear caudal posterior ventral margin.

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

Head rounded, length about 0.2 times total length, maximum width occurring just anterior of gill openings. Moderately rough tubercles interspersed above mouth and eye crests. Eyes almond-shaped, widely set, interorbital space 8.2 (7.7-8.9). Eye-spiracle space short. Spiracles are crescent shaped without large papillae. Interspiracle space (7.8-8.2) slightly less than interorbital space. Center of upper lip exposed at midpoint of upper jaw, exposure semi-circular in shape, extending dorsally approximately 0.6-0.7 of upper jaw space, upper lip height (1.2-2.1), upper lip arch width (3.8-5.1). Labial furrows conspicuous, roughly equal in length, extending from corners of mouth medially, with upper labial furrow partially covered with dermal folds. Distinct nasal flaps protruding from dermal folds above mouth, two barbels protruding from each flap. Inner nasal barbel rod-like with a spatulate tip, inner basal portion contains little if any fringe. Outer nasal barbel narrow. Nostrils large, slightly protruding. Dermal folds along exterior of head, one small lobe present at corners of mouth extending ventrally. Mouth length about 0.3 times as long as mouth width. Dentition consisting of small, dagger-like teeth, conical without cusplets on a broad base, in 3 orderly longitudinal rows, no teeth at symphysis, teeth by row 9 - 10 - 9 - 10 / 10 - 10.

Pectoral fins large, broadly rounded, originating just behind gills. Anterior margin of pectoral fin slightly convex and about three quarters as long as pectoral length, extending to a lateral apex. Angle of lateral apex slightly more obtuse than 120°. Margin from lateral apex to most posterior lobe slightly concave. Posterior lobe broadly convex. Pectoral inner margin convex, about one half of pectoral length.

Overall pelvic fin shape somewhat triangular with rounded fintips. Pelvics originating anterior to pectoral fin free rear tips. Pelvic fin length approximately two thirds as long as pectoral fin length. Pelvic fin base approximately 1.2 times broader than pectoral base. Anterior margin slightly curvilinear, extending at roughly a 45° angle from trunk to rounded apex lateral of body, anterior margin 0.5 times as long as pelvic fin length. Pelvic girdle width (26.3-29.8) between pelvic fin apexes moderately broad, about 1.4 times head length. Posterior margin of pelvic fin, approximately 0.8 times pelvic fin length, straight to posterior free tip. Pelvic inner margin concave and short, only about 0.4 times as long as pectoral fin length. Pelvic insertion furrows on ventral extend in a narrow ellipse to anterior apogee of vent in most specimens, vent is within ellipse. Pelvic fin tips reach origin of first dorsal.

Dorsal fins lobed and nearly equal in size, with denticles covering the whole of fins. Interdorsal space about 0.8 times as long as dorsal caudal finspace. Anterior margin of dorsals slightly convex, nearly equidistant. First dorsal base slightly shorter than second, first dorsal base 15.2 (10.0-11.8), second dorsal base 17.4 (13.0-15.0). Apex of dorsals lobed. Posterior margins slightly convex, about 0.7 times as long as anterior margins. Inner margins of dorsals slightly convex, approximately 0.7 times as long as anterior margins.

Caudal peduncle compressed dorso-ventrally with lateral longitudinal ridges, tapering posteriorly. Caudal fin lobe-like, markedly at dorsal apex. Caudal dorsal margin broadly rounded, about 0.8 times as long as preventral caudal fin margin. Subterminal caudal fin margin approximately half as long as caudal upper post ventral margin. Caudal lower postventral margin convex, approximately 0.8 times as long as caudal upper post ventral margin.

Total vertebrae 137-139; total precaudal vertebrae 107-110; monospondylous vertebrae 48-52; diplospondylous vertebrae 58-59; caudal vertebrae 29-30.

Coloration. Dorsal surface of specimens prior to preservation are light to dark brown throughout with numerous black and white spots of varying sizes. Black blotches laterally at origin of dorsals. Ventral surface pale white with some black mottling on abdomen, pectoral and pelvic fin ventral margins with denticles colored similar to dorsal. Color after preservation tends to fade to a lighter brown or pale yellow with spots becoming indistinct.

Distribution. Endemic to western North Pacific including the East China Sea (Compagno et al, 2005a), waters surrounding northern Taiwan, and East Taiwan Strait (Shuyuan 1994).

Etymology. Named in allusion to the known geographic range (Formosa Strait, Taiwan) where the holotype was collected.

Remarks. Examination of the holotype (labeled NTT7213130 in Shen & Ting 1972, now labeled NTUM 01329) and non-type comparison material revealed that S. formosa is distinct from other WNP squatinids through four characters (Fig 2). First, S. formosa possesses a lobed caudal fin, especially in the dorsal lobe, and has a more curved postventral caudal margin. Second, S. formosa has lobed dorsal fins with a curvilinear anterior margin. Third, the pelvic girdle distance in S. formosa is more narrow than other WNP squatinids, at 1.4 or less the head length (where both measurements are standardized by total length). Fourth, S. formosa has an upper lip arch which is semicircular in shape, where the upper lip arch height is greater than 1.5% of the total length.

Comparison of the three S. formosa paratypes (originally labeled as NTU7041631, NTU7041632, NTU7222433 in Shen and Ting 1972; now labeled as NTUM 01327(x2) and NTUM01328) with the holotype reveals differences among these four characters (Table 2). The paratypes possess angular caudal fins without curved postventral caudal margins, angular dorsal fins with straight anterior margins, a wider pelvic girdle distance, and upper lip arches which are more semi-oval in shape (Fig 3A-C). Therefore, our contention is that these paratypes of S. formosa are, in fact, a different species. Furthermore, these characters are most consistent with the S. nebulosa comparison material we examined.

An apparent change in designation of one of the paratypes for unknown reasons has also added to the confusion in the type series. At present, one of the paratypes (NTUM 01328) has been designated as the holotype, and the true holotype (NTUM 01329) now has a question mark on its catalogue card next to its holotype designation, as documented by the junior author (DAE) who examined the type material of S. formosa in May 1988 and again in May 2005. However, comparison of the type material with photos of the holotype within the original species description (Shen & Ting, 1972) confirms that the NTUM 01329 specimen is the actual holotype.

A squatinid reported from the Philippines as S. formosa (Compagno et al., 2005b) is also not likely this species. Examination of photographs of the Philippines specimen, provided by L.J.V. Compagno, revealed several characters inconsistent with S. formosa . These characters include pelvic fins which do not reach the first dorsal base, a wider pelvic girdle, a more shallow upper lip arch and distinctly different coloration than observed in S. formosa . Therefore, the Philippines specimen most likely represents a different, possibly undescribed, squatinid species from true S. formosa .

Material Examined. Type material: Holotype S. formosa : NTT7213130 (now labeled as NTUM 01329), immature female, Tung-Kang, Pingtung, Taiwan, 31 Jan 1972, identified by S.C. Shen. Paratypes S. formosa : NTU7222433 (now labeled as NTUM 01327) , and NTU7041632 (now labeled as NTUM 1327), caught 3 km off the coast of Tahsi, Taiwan (24°56.5’N, 121°53.0’E) in single trawling net at 100-120 fathoms, 16 Apr 1970, collected by W.H. Ting, identified by S.C. Shen ; NTU7041632 (now labeled as NTUM 01328), immature female, Tahsi, Taiwan, 24 Feb 1972, collected by W.H. Ting, identified by S.C. Shen .

Comparative material: DAE 881805, immature male, Tahsi, Taiwan, May 1988, collected by David A. Ebert ; DAE 052105, immature male, Tahsi, Taiwan, May 2005, collected by David A. Ebert ; DAE 052305-2, immature female, Tahsi, Taiwan, May 2005, collected by David A. Ebert .