Platyrhina tangi Iwatsuki, Zhang and Nakaya

Iwatsuki, Yukio, Miyamoto, Kei, Nakaya, Kazuhiro & Zhang, Jie, 2011, A review of the genus Platyrhina (Chondrichthys: Platyrhinidae) from the northwestern Pacific, with descriptions of two new species, Zootaxa 2738, pp. 26-40 : 37-38

Platyrhina tangi Iwatsuki, Zhang and Nakaya sp. nov.

New English name: Yellow-spotted Fanray Japanese name: Uchiwazame

Figs. 2 C–D, 3D–F, 4, 5; Table 1

Platyrhina sinensis (not of Bloch and Schneider); Müller and Henle, 1841: 125, pl. 44 (type locality: Japan and China [see comments under Synonymy of Platyrhina sinensis ]; in part, RMNH D.2696–D.2697; see Remarks); Richardson, 1846: 196 (Canton, China asYellow spotted ray); Günther, 1870: 471 ( China, probably same specimen examined by Richardson above; noted “A row of spines along the median line of the back and tail”); Fowler, 1930: 134, fig. 17 ( Japan); Fowler, 1941: 329 ( China and Japan); Matsubara, 1955: 135 ( China Sea and central Honshu southward, Japan); Chyung, 1977: 90, pls. 16-2, 16-3, 16-4 (southern Korea); Shen, 1984: 4, pl. 4-8-1 ( Taiwan); Nakaya, 1984: 12, pl. 13-H (southern Japan to China Sea); Chu and Wu, 1984: 63, fig. 35 ( China, southwestern Korea, southern Japan, South China Sea, Taiwan Strait, East China Sea and Yellow Sea); Chen, 1997: 7, unnumbered color photograph (South China Sea to Yellow Sea, western Pacific); Compagno and Last, 1999: 1432 (northwestern Pacific); Hatooka, 2002: 161 (southern Japan and East China Sea); Carvalho, 2004: 77, fig. 2A, 9A (South and East China Sea, western Pacific Ocean); Compagno et al., 2005: 63 (northwestern Pacific).

Discobatus sinensis: Temminck and Schlegel, 1850: 307 (Nagasaki, Japan); Snyder, 1912: 401 (Tokyo, Japan); Garman, 1913: 289, pls. 56, 66, fig. 8 ( Japan); Tanaka, 1951: 17, fig. 30 (southern Japan and southern China); Cheng, 1955: 30, fig. 21 (Port Arthur, Peitaiho, Chefoo and Qingdao, China).

Holotype. MUFS 23163, male, 398 mm TL, Meitsu, Miyazaki, Japan (31°32’12”N, 131°24’16”E), set net, coll. K. Miyamoto and Y. Iwatsuki, 27 June 2007.

Paratypes (90−637 mm TL, n =13). KPM-NI 2488 and 3616, 2 females, 434 and 637 mm TL, Mera, Kamogun, Shizuoka, Japan, set nets; KPM-NI 3205, male, 540 mm TL, Mera, Kamo-gun, Shizuoka, Japan, set nets; MUFS 23565 and 23718, female, 570 and 90 mm TL, Meitsu, Nango-cho, Miyazaki, Japan, set net, coll. K. Miyamoto, 21 Nov. 2007; MUFS 23717, male, 116 mm TL, Meitsu, Nango-cho, Miyazaki, Japan, set net, coll. K. Miyamoto, March 2008; MUFS 23727, male, 525 mm TL, Iorigawa, Kadokawa Bay, Miyazaki, Japan, set net, coll. H. Izumi; FFNU-P-00006, FFNU-P-00007, 2 males, 328 and 341 mm TL, off Shimabara, Nagasaki, Japan, trawls; FFNU-P-00005, FFNU-P-00008, FFNU-P-00009 and FFNU-P-00010, 4 females, 303–536 mm TL, off Shimabara, Nagasaki, Japan, trawls.

Non-type specimens (149–640 mm TL, n =20). MUFS 14132, female, 238 mm TL, Meitsu, Nango-cho, Miyazaki, Japan; MUFS 18295, female, 161 mm SL, off Aoshima, Miyazaki, Japan, trawls; MUFS 18314, male, 149 mm TL, Totoro, Nobeoka, Miyazaki, Japan; MUFS 23500, 23516 and 23546–23547, 4 males, 430–480 mm TL, Meitsu, Nango-cho, Miyazaki, Japan, set nets; MUFS 22500, 23517–23519, 23520–23521, 23548–23550, 23594–23595, 11 females, 90–640 mm TL, Meitsu, Nango-cho, Miyazaki, Japan, set nets; RMNH D2696–D2697, 2 females, 445–585 mm TL, coll. Bürger, Japan.

Diagnosis. Distinguished from congeners in having the following combination of characters: one row of thorns (weakly hooked, sometimes tubercle-like) on mid-dorsum of tail; thorns absent from anterior part of scapular region ( Fig. 3 E); thorns on the orbital, nape and scapular regions encircled by light yellow or white pigment ( Figs. 2 C–D, 3D–F); dorsal surface covered with minute and some clearly larger dermal denticles (coarse to touch).

Description. Counts and proportional measurements of the holotype, 13 paratype and 20 non-type specimens of Platyrhina tangi sp. nov. are shown in Table 1. Data for the holotype are presented first, followed by those of other specimens in parentheses.

Disk broadly wedge-shaped, snout tip slightly angular, outer margins broadly rounded, free rear tip reaching or slightly beyond level of cloaca; preorbital and preoral snout lengths 14% (11–14%) of TL and 13% (11–14%) of TL, respectively (Fig. 4); pelvic fins rounded (free rear tips angled), originating from abdominal surface at end of pectoral fins; tail shark-like, length greater than disc length, 57% (54–63%) of TL, abruptly narrower than disc width, lacking a caudal spine, abdominal surface flat with shallow groove along mid-abdominal axis; one row of thorns (weakly hooked, sometimes tubercle-like) on mid-dorsum of nape to second dorsal fin origin; dermal-lateral folds on tail, originating well anterior to free rear tip of pelvic fin, reaching just behind caudal fin origin; two widely separated dorsal fins on tail, similar in size and shape, moderately large, anterior margins slightly convex with convex hind margin; first dorsal fin originating 1.2 (1.2–1.5) times maximum disc width from snout tip, well behind free rear tips of pelvic fins but anterior to mid-length of tail; second dorsal fin originating 1.4 (1.4–1.7) times maximum disc width from snout tip; interdorsal space 1.1 (0.9–2.1) times first dorsal fin base length, 2 (1–2) thorns on mid-dorsum; caudal fin relatively small, flat, oval, sometimes forming small lobe posterodorsally, dorsal margin length 1.0 (0.9–1.1) times abdominal margin length; head moderately elongate; snout moderately long, soft, flexible; eyes moderately large, not elevated or protruding; spiracles leaf-shaped, 1.4 (0.9–1.6) times eye length, originating beside eyes; nostrils moderately large, nasal flap skirt-shaped; anterior aperture circular, lower part surrounded by short folds; mouth width moderate, upper and lower jaws arched, skin grooves around mouth; oral teeth small, rhomboid, slightly pointed in males, over 66 (56–127) regular rows on lower jaw (increasing with growth), upper and lower jaw teeth similar in shape and size; five pairs of gill openings, two anteriormost widely separated, distance between second to fifth gradually becoming narrower posteriorly; 5 (3–5) thorns (weakly hooked or tubercle-like) around on orbits; two pairs of two (total eight) symmetrical thorns on scapular region; 2 (0–11) subsequent irregular small thorns on two pairs of two symmetrical thorns ( Fig. 3 E, indicated by black arrows); thorns absent anteriorly on scapular region ( Fig. 3 E); thorns on the orbital, nape and scapular regions encircled by light yellow or white pigment (same in the above irregular thorns) ( Figs. 2 C–D, 3D–F); claspers of mature males greatly elongated; entire body and fins covered with minute dermal denticles, some clearly larger dermal denticles on dorsal surface (coarse to touch); irregular small thorns aggregated on anterodorsal margin of disk from snout tip to maximum disc width.

Color of fresh specimens. Based on holotype ( MUFS 23163) and 5 paratypes ( MUFS 18295, 23500, 23516 and 23546–23547) photographed by K. Miyamoto and Y. Iwatsuki: dorsal surface often brown, darker medially; dorsal and caudal fins brown; abdominal surface whitish, outer margins of pectoral and ventral fins broadly grayish-brown.

Color of preserved specimens. Dorsal surface often brown, darker medially; dorsal and caudal fins brown; abdominal surface whitish, outer margins of pectoral and ventral fins broadly grayish-brown.

Distribution. Platyrhina tangi sp. nov. is currently known from southern Japan (except the Ryukyu and Ogasawara Islands), southern Korea, China, Taiwan and northern Vietnam ( Fig. 5 ), but seems to be very rare in the Sea of Japan (Y. Kai, personal communication).

Ecological notes. Kume et al. (2008), who studied the vertebral centra of P. s i n e n s i s (= P. tangi sp. nov.), suggested that females attained a greater asymptotic total length (555.8 mm TL) and grew more slowly than males (455.2 mm TL) (based on specimens from Ariake Bay, western Kyushu Island, Japan). The maximum ages observed were 5 years (males) and 12 years (females). Furthermore, Yamaguchi and Kume (2009) reported that females reached sexual maturity at a greater size than males (total length at 50% sexual maturity: males, 393 mm; females, 421 mm). Parturition occurred from August to November followed immediately by mating, ovulation and fertilization. Fowler (1941) reported the largest specimen yet recorded (USNM 51295, 680 mm TL, Tokyo, sex unknown) of the species, the largest specimens examined during this study having been collected from the Hyuga Nada Sea (female, 639 mm TL; male, 525 mm TL). However, the species is likely to grow larger than ca. 700 mm TL according to local Miyazaki fishermen.

Etymology. The specific name, “ tangi ”, is proposed in honor of the Chinese ichthyologist D.-S. Tang.

Remarks. For erroneous identification of Platyrhina tangi sp. nov., see Remarks under P. s i n e n s i s.

Figures

FIGURE 2. Three species of Platyrhina and close up of tail for each species. A – C) Platyrhina sinensis, D – F) P. hyugaensis sp. nov. and G – I) P. tangi sp. nov. A) ASIZB 182251, male, 350 mm TL, off Amoy, China; B) ASIZB 182256, female, 455 mm TL, off Amoy, China; C) Same specimen of (A), close up of tail; D) MUFS 21609 (holotype), male, 391 mm TL, Meitsu, Miyazaki, Japan; E) MUFS 23164 (paratype), female, 431 mm TL, Meitsu, Miyazaki, Japan; F) Same specimen of (D), close up of tail; G) MUFS 23163 (holotype), male, 398 mm TL, Meitsu, Miyazaki, Japan; H) KPM-NI 2488 (paratype), female, 434 mm TL, Mera, Shizuoka, Japan; I) Same specimen of (G), close up of tail.

FIGURE 3. Differences between A – C) Platyrhina hyugaensis sp. nov. and D – F) P. t a n g i sp. nov.; A – C) MUFS 23164 (holotype), female, 431 mm TL, Meitsu, Miyazaki, Japan; D – F) KPM-NI 2488 (paratype), female, 434 mm TL, Mera, Shizuoka, Japan. White and black arrows show a pair of thorns on the anterior part of scapular region and subsequent irregular small thorns on two pairs of two (total eight) symmetrical thorns, respectively.

FIGURE 5. Distribution of Platyrhina sinensis, P. hyugaensis sp. nov. and P. t a n g i sp. nov. Black dots based on specimens examined during this study; white dots based on literature records (as P. s i n e n s i s).