Sinobatis bulbicauda Last & Séret, 2008, new species
Creators: name: Last, Peter R.
name: Séret, Bernard
Publisher: name: Zenodo
Year: 2008
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Elasmobranchii
Rajiformes
Anacanthobatidae
Sinobatis
Sinobatis bulbicauda

description: Sinobatis bulbicauda new species
Figs 1, 3–5, 11, 13; Table 1
Anacanthobatis sp. A: Last & Stevens, 1994, Sharks and rays of Australia, pp 357–8, fig. 35.1, key fig. 3, text figs, pl. 64; Last & Compagno, 1999, Anacanthobatidae, leg skates. In: Carpenter & Niem (eds), 1999, FAO species identification guide for fisheries purposes. The marine living resources of the Western Central Pacific, pp 1466, figs. Anacanthobatis sp.: Séret, 1994 (abstract)
Holotype. CSIRO H 2557–01, adult male, 429 mm TL (261 mm DW), 612–620 m depth, W of Cape Farquhar, Western Australia (23°44'S, 112°35'E), 1991.
Paratypes. 33 specimens: AMS I 31167–003 (3 specimens), female, 244 mm TL (115 mm DW), female, 258 mm TL (135 mm DW) and female, 328 mm TL (158 mm DW), 1115–1125 m depth, W of Dirk Hartog Island, Western Australia (25°41'S, 111°30'E), 1991; CSIRO B 4007, female, 189 mm TL (68 mm DW), 402– 404 m depth, NW shelf, Western Australia (18°54'S, 116°11'E), 1984; CSIRO CA 2809, female, 555 mm TL (321 mm DW), 150 m depth, N of Forestier Island, Western Australia (18°41'S, 117°58'E), 1982; CSIRO CA 2825, adult male, 433 mm TL (271 mm DW), 590–592 m depth, N of Nickol Bay, Western Australia (18°45'S, 116°26'E), 1982; CSIRO CA 3566, juvenile male, 287 mm TL (165 mm DW), 496–504 m depth, SW of Rowley Shoals, Western Australia (17°39'S, 118°32'E), 1983; CSIRO CA 4371, female, 321 mm TL (163 mm DW), 500–504 m depth, NE of Rowley Shoals, Western Australia (15°40'S, 120°37'E), 1984; CSIRO H 1213–2, female, 388 mm TL (212 mm DW), 420 m depth, Ashmore Terrace area, Western Australia (13°25'S, 122°54'E), 1988; CSIRO H 1514–23, female, 297 mm TL (163 mm DW), 447–582 m depth, NW of Port Hedland, Western Australia (18°14'S, 117°54'E), 1988; CSIRO H 1621–3, juvenile male, 265 mm TL (120 mm DW), 430 m depth, Rowley Shoals area, Western Australia (18°36'S, 117°19'E), 1988; CSIRO H 1647–3, juvenile male, 170 mm TL (80 mm DW) and juvenile male, 278 mm TL (131 mm DW), 400–450 m depth, SW of Rowley Shoals, Western Australia (17°18'S, 119°12'E), 1988; CSIRO H 1650–3, juvenile male, 161 mm TL (78 mm DW) and CSIRO H 1650–4, juvenile male, 329 mm TL (137 mm DW), 425 m depth, SW of Rowley Shoals, Western Australia (18°36'S, 117°20'E), 1988; CSIRO H 1819–4, juvenile male, 359 mm TL (183 mm DW), 437 m depth, W of Gantheaume Bay, Western Australia CSIRO H 3159–06, female, 536 mm TL (303 mm DW) and CSIRO H 3159–07, female, 560 mm TL (334 mm DW), 555 m depth, NW of Dampier Archipelago, Western Australia (18°48'S, 116°07'E), 1992; CSIRO H 4071–02, juvenile male, 125.4 TL (62 mm DW), 388–392 m depth, SW of Rowley Shoals, Western Australia (18°06'S, 118°10'E), 1995; CSIRO H 6417–04, female, 461 mm TL (222 mm DW), 886–907 m depth, NW of North West Cape, Western Australia (19°35'S, 113°20'E), 2006; MNHN 2007–1472, adolescent male 342 mm TL (155 mm DW), 443– 468 m depth, Tanimblar Island, Indonesia (07°46'S, 132°31'E), 1991; MNHN 2007–1471, late adolescent male 362 mm TL (181 mm DW), 214–215 m depth, Tanimblar Island, Indonesia (08°00'S, 132°58'E), 1991; NTM S 12592 –013, juvenile male, 312 mm TL (160 mm DW), 445 m depth, off Rowley Shoals, Western Australia (17°24'S 118°54'E), 1985; NTM S 12614 –039, juvenile male, tail damaged (164 mm DW), 410 m TABLE 1 Morphometric data for the mature male holotype of Sinobatis bulbicauda sp. nov. (CSIRO H 2557–01), with ranges for male (n=6) and female (n=7) paratypes. Total lengths (TL) are expressed in mm, other measurements as percentages of TL.
Sinobatis bulbicauda sp. nov.
Males (n=6) Females (n=7)
Holotype Min. Max. Min. Max. depth, off Rowley Shoals, NW Shelf, Western Australia (17°39'S 118°38'E), 1985; WAM P 28088–002, adolescent male, tail damaged (203 mm DW), 437–442 m depth, 60 km SW of Rowley Shoals, NW Shelf, Western Australia (17°55'S, 118°22'E), 1983; WAM P 28089–007, female, 284 mm TL (149 mm DW), 418–419 m depth, 75 km SW of Rowley Shoals, Western Australia (17°58'S, 118°18'E), 1983; WAM P 28092–001, female, 309 mm TL (174 mm DW), 440–442 m depth, 90km SW of Rowley Shoals, Western Australia (18°05'S, 118°08'E), 1983; WAM P 28094–001, juvenile male, 233 mm TL (111 mm DW), 431–433 m depth, 70 km SW of Rowley Shoals, Western Australia (17°57'S, 118°19'E), 1983.
Diagnosis. A species of Sinobatis with the following combination of characters: moderate-sized disc (width at anterior orbit 5.2–7.8 times mouth width); moderately elongate to short tail (postcloacal length 79– 170% of disc length); relatively large eyes, orbit diameter 4.7–8.8 in horizontal snout and 6.7–10.6 in head lengths respectively; distal portion of tail expanded laterally in specimens exceeding about 280 mm TL (130 mm DW), width of tail near tip 1.3–2.2 times tail width at its midlength; pectoral-fin radials 66–71; moderatesized pelvic fins, anterior lobe 12.1–18.1% TL; anterior pelvic-fin lobe rather broad-based, width 1.7–3.2 in distance between pelvic-fin origins; caudal fin rudimentary; 20–28 tooth rows in each jaw of adults; teeth of adult males with greatly elongated conical cusps; abdominal vertebral centra 25–31, total centra 148–171; dorsal surface pale pinkish brown, ventral surface uniformly pale.
Description. Small anacanthobatid with extremely depressed pear-shaped to broadly heart-shaped disc (extremely variable between growth stages and between sexes), its width 0.98 in holotype (0.94–1.17 in male paratypes, 1.09–1.23 in female paratypes) in length from base of rostral filament; axis of maximum width at 61% (57–64%, 55–63%) of disc length, outer and inner corners broadly rounded. Tail short, very slender, its width uniform anteriorly; horizontally expanded posteriorly (not expanded in neonate paratypes), compressed, becoming spatulate and forming a broad, lobe-like filament; becoming compressed just before caudal fin, filamentous near tip; length much shorter than trunk length (much longer in neonatal paratypes), cloaca to tip of tail 1.27 (0.67–1.22, 0.74–1.59) in snout-cloaca length (from base of rostral filament), 1.37 (0.83–1.40, 0.65– 1.55) in disc width, 1.35 (0.79–1.34, 0.80–1.70) in disc length; no lateral cutaneous folds. Head relatively short to moderately elongate, dorsal length 27.2% (21.4–25.9%, 20.7–30.8%) TL, ventral length 34.4% (23.4–33.3%, 25.9–36.1%) TL. Snout relatively short, its preorbital length 4.76 (3.92–4.44, 3.38–5.71) times longer than interorbit, 21.6% (15.1–20.1%, 15.0–25.2%) TL; angle forward of spiracles acute, about 81° (80– 84° in adults and subadults, 88–98° in neonates and early juveniles); snout tip with a short subtriangular rostral lobe; short, broad filament at apex of rostral lobe. Orbits variable in size, large to medium sized, horizontal diameter 6.57 (4.74–6.62, 4.91–8.76) in preorbital snout length, 1.38 (1.13–1.63, 1.37–1.66) in interorbit. Spiracles very small, much less than half length of orbits, subcircular to ovoid; combined orbit and spiracle length 4.4% (3.9–4.9%, 3.9–4.6%) TL. Mouth strongly convex in holotype, upper jaw strongly concave at symphysis (less so in female paratypes and juveniles, often almost straight); width 3.77 (3.57–4.02, 3.67– 5.31) in preoral length, 5.58 (5.08–5.72, 5.27–6.67) in ventral head lengths; teeth with an irregular oval base, subcircular crown with very long conical cusps (slightly less pronounced in adult male paratype, CSIRO CA 2825); female paratype (CSIRO H 3159–07) with broadly oval to rhomboidal crowns, short posterior cusps; teeth in small female paratype (CSIRO H 1213–02) similar to those of larger female paratype above. Anterior nasal lobes small, weakly fringed, confined to anterior lateral margins of nostril; oronasal grooves well developed. Posterior nasal lobes enlarged, weakly connected basally at isthmus by low, fleshy, concave skin folds; not united medially, not forming a well-defined nasal curtain; with prominent, simple or multifurcate (mostly bifurcate), dermal fringe along posterior margin; overlapping corners of mouth (not overlapping in paratypes). Rostral cartilages flexible, strongly undulated (more so distally). Upper and lower surfaces of disc and tail entirely naked, except for alar thorns in adult males; holotype with 2 (3) longitudinal rows of sharp, strongly recurved, non-retractable alar thorns, 12–13 (17–18) on each pectoral fin; thorn patch located at level just posterior to apex of fin, length of patch about equal to interorbit, width about equal to eye diameter. Mucous pores around spiracle and eye distinct (dark edged); 3–4 (2–4) pores lateral to eye and spiracle, usually with a pair medial to each spiracle, and a single postcranial pore on each side of midline; less distinct pores elsewhere on disc; minute fleshy papillae sometimes on dorsal surface near orbit; skin thin on dorsal surface, mildly deciduous (particularly on mid-disc and near disc apex), less deciduous ventrally. Anterior margin of disc undulated, weakly concave (less so in females and juveniles), almost straight along rostrum; interspiracular distance 4.79 (4.25–6.26, 4.13–6.31) in width at anterior margin of orbit, 4.02 (3.39–3.97, 3.32–4.74) in dorsal head length, 2.06 (1.81–2.46, 2.04–2.49) times orbit diameter; posterior pectoral-fin margins strongly convex, pectoral axils fused to dorsolateral margin of posterior pelvic-fin base in male holotype (almost entirely fused with anterior lateral margins of posterior pelvic lobes in female and juvenile paratypes, posterior half of disc appearing semicircular). Anterior lobes of pelvic fins slender, freely articulating at base, leg-like, well separated from posterior lobes; base of anterior lobes closer together in adult males than females. Posterior pelvic-fin lobes narrowly rectangular, length 1.18 (0.99–1.35, 1.01–1.50) of anterior lobe length, their posterior margins fused to lateral margin of tail just forward of their distal tip in holotype (completely fused along entire length with base of tail in female and juvenile paratypes). Clasper greatly elongate (extending to almost midlength of tail), slightly depressed, glans slightly expanded, capable of strong distal evertion (components displayed when everted); distal lobe minute; everted clasper broader near hypopyle that at base; pseudosiphon, spur and palp absent; inner dorsal lobe with two shallow proximal clefts; well-developed rhipidion at level of hypopyle; shield very small, without pent; sentinel and spike elongate, similar in size and shape, dagger-like, both slightly dorsoventrally flattened distally; spike directed medially, partly enveloped by dorsal lobe when clasper everted; sentinel directed laterally away from glans when clasper everted. Caudal fin rudimentary, barely detectable. No dorsal fins. Tooth rows in upper jaw 21 (21–26); in lower jaw 20 (21–28). Vertebrae: monospondylous centra 28 (25–31), diplospondylous centra 143 (121–142), total centra 171 (148– 168). Pectoral fin: propterygial radials: 23 (22–26), mesopterygial radials 16 (16–21), metapterygial radials 27 (25–28), total radials 66 (66–71). Pelvic fin: in males 3 (3–4) + 12 (12–14) radials; females 3–4 + 14–16 radials.
Colour. Fresh and preserved: Upper surface of disc and anterior tail pale greyish pink; whitish along disc margin, posterior tail and where skin removed; much darker brown around alar thorns and on posterior pelvic lobe; orbito-spiracular pores dark edged; claspers and anterior lobe of pelvic fin whitish; eyeballs bluish black, visible beneath skin dorsally. Ventral surface of disc and tail uniformly pale or white, skin somewhat translucent.
Size. To at least 54 cm TL (disc width 33 cm); smallest adult male 43 cm TL (disc width 26 cm); smallest neonatal juvenile 12.5 cm TL (disc width 6 cm).
Distribution. Lower continental shelf and upper to mid continental slope of Western Australia from west of Gantheaume Bay (27°49'S, 113°01'E), northwards to Ashmore Terrace (13°25'S, 122°54'E) in depths of 150–1125 m (mostly 400–800 m), and off Tanimblar Island, eastern Indonesia (07°46'– 08°00'S, 132°31–58'E) in 214– 468 m.
Etymology. Derived from the Latin bulbus (swelling) and cauda (tail, appendage) with reference to the flattened expansion of the tail near its tip. Known in the vernacular as Western Australian Legskate.
Remarks. A distinctive species of Sinobatis that, unlike any other related species from the Indo-Pacific, has an unusual distally flattened tail in all but the smallest individuals. Sinobatis bulbicauda is a mediumsized member of the genus that has affinities to a slightly smaller species, S. borneensis, from the South and East China Seas. Based on Chans'(1965) description of the adult male holotype, S. borneensis has a filamentous (rather than bulbous) tail and the snout is relatively longer (preorbital length 6.5 times the interorbital length vs. 3.9–4.8 in adult males and 3.4–5.7 in all types of S. bulbicauda). Adult males of the two species are not identical in size (317 mm TL in S. borneensis, 429–433 mm TL in S. bulbicauda) but are similar enough to ensure that morphometric biases due to ontogenetic variability are minimal.
The adult males of the two species also differ in their relative disc widths (66.2% TL in S. borneensis vs. 60.8–62.5% TL in S. bulbicauda), precloacal lengths (58.4% vs. 54.6–56.1% TL), preoral lengths (25.2% vs. 21.4–23.2% TL), orbit diameters (2.3% vs. 2.9–3.3% TL), mouth width (6.6% vs. 5.8–6.2% TL), and intergill distances (11.4% vs. 11.8–12.9% TL between first gill slits, 6.8% vs. 7.2–7.3% TL between fifth gill slits). Based on Seret (1986), the holotypes of S. borneensis (BMNH 1965.1.29.1) and S. melanosoma (USNM 198121) have more pectoral-fin radials (75–76 and 75 respectively vs. 66–71 (n=14), mainly 68–69, rarely 70 or more in S. bulbicauda). Another specimen of S. borneensis from the Philippines (MNHN 1997.3321) had 71–72 pectoral-fin radials. Unlike S. bulbicauda, S. melanosoma has a dark dorsal and ventral disc (rather than pale dorsally and white ventrally), and a rat-like tail without a lateral distal expansion.
description: Published as part of Last, Peter R. & Séret, Bernard, 2008, Three new legskates of the genus Sinobatis (Rajoidei: Anacanthobatidae) from the Indo – West Pacific, pp. 33-58 in Zootaxa 1671 on pages 37-43, DOI: 10.5281/zenodo.180189