Sinobatis filicauda, Last, Peter R. & Séret, Bernard, 2008

Last, Peter R. & Séret, Bernard, 2008, Three new legskates of the genus Sinobatis (Rajoidei: Anacanthobatidae) from the Indo – West Pacific, Zootaxa 1671, pp. 33-58 : 49-57

Sinobatis filicauda new species

Figs 9–13 ; Table 3

Anacanthobatis sp. B: Last & Stevens, 1994, Sharks and rays of Australia, pp 357, 359, fig. 35.2, key fig. 4, 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.

Holotype. CSIRO H 948–02, adult male, 548 mm TL (341 mm DW), 678–695 m depth, Saumarez Plateau, Queensland (22°56'S, 154°24'E), 1985.

Paratypes. 5 specimens: CSIRO H 1167–04, female, 254 mm TL (110 mm DW), 696 m depth, Queensland Plateau, W of Lihou Reef and Cays, Queensland (17°02'S, 151°03'E), 1985; CSIRO H 1240–02, female, 100 mm TL (35 mm DW), 606–610 m depth, Queensland Plateau, Queensland (17°06'S, 150°52'E), 1985; CSIRO H 2474–01, female, 392 mm TL (193 mm DW) and CSIRO H 2476–01, juvenile male, 386 mm TL (195 mm DW), 792–802 m depth, NW of Lihou Reefs and Cays, Queensland (17°01'S, 151°20'E), 1985; CSIRO H 2479–01, female, 508 mm TL (368 mm DW), 880 m depth, Queensland Plateau, Queensland (16°55'S 151°34'E), 1985.

Diagnosis. A species of Sinobatis with the following combination of characters: large disc (width at anterior orbit 5.7–8.1 times mouth width); short tail (postcloacal length 97–140% of disc length); relatively large eyes, orbit diameter 7.1–9.6 in horizontal snout and 9.4–11.3 in head lengths respectively; distal portion of tail not expanded, width of tail near tip 0.7–1.1 times tail width at its midlength; pectoral-fin radials 71–75; moderate-sized pelvic fins, anterior lobe 14.8–16.2% TL; anterior pelvic-fin lobe rather broad-based, width 1.6–2.5 in distance between pelvic-fin origins; caudal fin rudimentary; 18–22 tooth rows in each jaw of adults; teeth of adult males with very short cusps; monospondylous vertebral centra 27–30, total centra 155–182; dorsal surface uniformly pale pinkish brown, ventral surface pale, translucent.

A B

B A B Sinobatis filicauda sp. nov.

Male Females (n=3)

Holotype Min. Max. Description. Small to medium-sized anacanthobatid with extremely depressed, broad pear-shaped disc (extremely variable between growth stages and between sexes), its width 0.99 in holotype (1.13 in male paratype, 1.15–1.22 in two female paratypes) in length from base of rostral filament; axis of maximum width at 61% (61%, 58–67%) of disc length, outer and inner corners broadly rounded. Tail relatively elongate (when undamaged), very slender, slightly depressed anteriorly; in cross-section, midlength almost flat ventrally, convex dorsally; barely expanded posteriorly, not spatulate; tapering distally to form a slender filament; length much shorter than trunk length, cloaca to tip of tail 1.26 (1.08, 0.95–1.18) in snout-cloaca length (from base of rostral filament), 1.42 (1.06, 0.84–1.07) in disc width, 1.40 (1.20, 0.97–1.31) in disc length;no lateral cutaneous folds. Head moderately elongate, dorsal length 26.6% (27.2%, 27.6–28.5%) TL, ventral length 32.3% (32.0%, 31.7–33.7%) TL. Snout of moderate-sized, its preorbital length 4.10 (5.07, 4.48–5.05) times longer than interorbit, 22.2% (22.6%, 22.3–24.1%) TL; angle forward of spiracles acute, 88° (76–86° in adults and juveniles, 103° in neonate); snout tip with a relatively short, broad, subtriangular rostral lobe; short filament at apex of rostral lobe. Orbits of medium size, horizontal diameter 7.13 (7.89, 8.53–9.56) in preorbital snout length, 1.74 (1.56, 1.69–1.98) in interorbit. Spiracles very small, much less than half length of orbits, subcircular to suboval; combined orbit and spiracle length 4.5% (4.00%, 3.8–4.0%) TL. Mouth weakly convex anteriorly, inner margin of upper jaw weakly concave at symphysis; width 3.87 (5.35, 4.98–5.21) in preoral length, 5.45 (7.08, 6.53) in ventral head length; teeth with an irregular oval base, an elevated, flattened crown and short posterior cusp (less well developed in female and juvenile paratypes); cusps enlarged slightly near middle of jaws on male holotype. Anterior nasal lobes with weak fringe, barely discernable, confined to anterior lateral margins of nostril; oronasal grooves well developed. Posterior nasal lobes enlarged, weakly connected basally by low, fleshy, concave skin folds; not united medially, not forming a well-defined nasal curtain; lobe with prominent, simple or multifurcate (mostly bifurcate) dermal fringe along posterior margin; not overlapping corners of mouth. Rostral cartilage prominent, flexible, strongly curved. Upper and lower surfaces of disc and tail entirely naked, except for alar thorn patch in adult male holotype; patch with 3 rows of sharp, strongly recurved, non-retractable alar thorns; 17–19 thorns on each pectoral fin; thorns directed posteromedially; thorn patch located at level just posterior to apex of fin, length of patch about equal to interorbital distance, width subequal to orbit diameter. Mucous pores on dorsal surface distinct, dark edged (indistinct in paratypes), well developed around orbit, 2–3 (2–3) pores lateral to eye and spiracle; damaged (usually 2) pores medial to spiracle, and a single postcranial pore on each side of midline; a few minute tubelike papillae on dorsal surface, barely detectable without magnification; skin thin on dorsal surface, somewhat deciduous, less deciduous ventrally. Anterior margin of disc concave, (most pronounced in holotype beside orbit; preorbital margin of paratypes almost straight; interspiracular distance 4.88 (5.69, 4.34–5.67) in width at anterior margin of orbit, 3.88 (4.25, 4.09–4.40) in dorsal head length, 2.42 (2.24, 2.58) times orbit diameter; posterior half of disc almost semicircular in females and juvenile paratypes; posterior pectoral-fin margins almost uniformly rounded, insertion deeply incised; pectoral axils fused to dorsolateral margin of posterior pelvic-fin lobe well posterior to base of anterior pelvic-fin lobe (fused to margin of posterior pelvic-fin lobe at a point between a half and two-thirds its length in paratypes). Anterior lobes of pelvic fins not especially broad, depressed, freely articulating at base, leg-like, well separated from posterior lobes; posterior lobes subrectangular (narrowly suboval in paratypes), length 1.03 (0.92, 1.04–1.24) of anterior lobe length, their posterior margins fused to ventrolateral margin of tail just forward of their distal tip. Clasper greatly elongate (extending just short of midlength of tail), suboval, glans distinctly enlarged (adult male not everted); distal lobe minute; pseudosiphon, spur and palp absent; inner dorsal lobe with two shallow proximal clefts; well-developed rhipidion at level of hypopyle; shield very small, inobvious, without pent; sentinel and spike elongate, similar in size and shape, recurved distally, apices pungent; clasper of holotype not everted. Caudal fin short, very low, barely detectable, epichordal lobe longer (about or much less than mouth width) than hypochordal lobe. No dorsal fins. Tooth rows in upper jaw 22 (18–21), neonate (CSIRO H 1240–02) with about 14; in lower jaw 22 (20), neonate with about 14. Vertebrae: monospondylous centra 30 (27–29), diplospondylous centra 152 (126–140), total centra 182 (155–167). Pectoral fin: propterygial radials: 23 (24–26), mesopterygial radials 20–21 (18–20), metapterygial radials 29 (29–30), total radials 72–73 (71–75). Pelvic fin: in males 3 + 13 radials (holotype CSIRO H 948–02); females 3–4 + 15–16 radials.

Colour. In preservative, upper surface of disc and anterior tail pale greyish pink (paratypes paler), white on snout tip, along disc margin, posterior tail, and where skin removed; darker brown around alar thorns; postspiracular pores weakly dark edged (less distinct in some paratypes); claspers and anterior lobe of pelvic fin white; eyeballs bluish black, visible beneath skin dorsally. Brownish dorsally before preservation. Ventral surface of disc uniformly pale, strongly translucent (often with pink tinge), viscera and radials clearly visible; tail uniformly pale or white.

Size. To at least 55 cm TL (disc width 37 cm); only adult male 55 cm TL (disc width 34 cm); smallest neonatal juvenile 10 cm TL (disc width 3.5 cm).

Distribution. Upper continental slope off Queensland from the southeastern sector of the Saumarez Plateau (22°58'S, 154°26'E) northwards to the Queensland Plateau (16°54'S, 151°30'E), in depths of 606– 880 m.

Etymology. Derived from the Latin filum (thread) and cauda (tail, appendage) with reference to its thread-like tail tip. Known in the vernacular as Eastern Australian Legskate.

Remarks. Sinobatis filicauda resembles S. bulbicauda morphologically and in coloration but they are easily distinguished by the shape of the posterior tail which is thin and tapering slightly in S. filicauda (width of tail near tip 0.7–1.1 times width at midlength) and expanded laterally in S. bulbicauda (width of tail near tip 1.3–2.2 times width at midlength). The species also appear to vary slightly in some body ratios. For example, the interorbital width in males is 1.6–1.7 (vs. 1.1–1.6 in S. bulbicauda ) times and in females 1.7–2.0 (vs. 1.4– 1.7) times the orbit diameter, and the horizontal preorbital length in males is 7.1–7.9 (vs. 4.7–6.6) times and in females 8.5–9.6 (vs. 4.9–8.8) times the orbit diameter. Sinobatis filicauda has more pectoral radials than S. bulbicauda (72–77 vs. 68–71), and has a relatively smaller head (ventral head length 32–34% vs. 38–42% TL) and paler disc than both S. caerulea and S. melanosoma (pale brownish dorsally and pale translucent ventrally vs. dark on both surfaces) and is never bluish on the dorsal surface. It reaches a larger size than S. borneensis .

Figures

FIGURE 9. Sinobatis filicauda sp. nov., holotype, CSIRO H 948 – 02, 548 mm TL, adult male: A, dorsal surface; B, ventral surface.

FIGURE 10. Sinobatis filicauda sp. nov., paratype, CSIRO H 2479 – 01, 508 mm TL, female: dorsal surface.

FIGURE 11. Dorsal view of posterior tail of: A, Sinobatis bulbicauda sp. nov., holotype, CSIRO H 2557 – 01, 429 mm TL, adult male; B, S. caerulea sp. nov., holotype, CSIRO H 2550 – 10, 539 mm TL, immature male; C, S. filicauda sp. nov., holotype, CSIRO H 948 – 02, 548 mm TL, adult male.

FIGURE 12. Oronasal region and tooth bands of Sinobatis filicauda sp. nov.: A, holotype, CSIRO H 948 – 02, 548 mm TL, mature male; B, paratype, CSIRO H 2479 – 01, 508 mm TL, female.

FIGURE 13. Distributional ranges of Australian Sinobatis species: S. bulbicauda sp. nov. (light grey), S. caerulea sp. nov. (dark grey), S. filicauda sp. nov. (black). The type locations are given for each species: S. bulbicauda (black circle), S. caerulea (black star) and S. filicauda (white star).

Tables

TABLE 3 Morphometric data for the mature male holotype of Sinobatis filicauda sp. nov. (CSIRO H 948 – 02), with ranges for single male and female (n = 3) paratypes. Total lengths (TL) are expressed in mm, other measurements as percentages of TL.

Total length (TL)	548	386	254	392
Disc width (DW)	62.2	50.5	43.4	49.2
Disc length	61.3	57.0	50.0	59.8
Snout - pectoral insertion	53.9	57.2	54.6	59.6
Snout - axis of maximum width	37.0	34.6	33.4	34.7
Snout - cloaca	55.2	51.5	48.6	54.2
Head length (dorsal)	26.5	27.2	27.6	28.5
Head length (ventral)	32.3	32.0	31.7	33.7
Snout length (preorbital)	20.7	22.3	22.5	24.5
Snout - spiracle	24.6	26.7	27.2	27.7
Snout length (preoral)	22.9	24.2	25.3	25.7
Prenasal length	19.2	21.7	22.4	24.0
Orbit diameter	2.8	2.9	2.5	2.6
Orbit and spiracle length	4.5	4.0	3.8	4.0
Spiracle length	1.2	0.6	0.5	0.6
Distance between orbits	4.9	4.5	4.4	5.0
Distance between spiracles	6.8	6.4	6.5	6.7
Mouth width	5.9	4.5	4.9	5.2
Distance between nostrils	6.0	4.7	4.2	4.7
Head width (at anterior margin of orbits)	33.4	36.4	29.2	36.8
Nare - mouth	4.5	2.3	2.2	2.7
Nasal curtain length	3.3	2.6	2.0	2.3
Nasal curtain width	7.4	6.2	5.4	5.9
Nasal curtain lobe width	2.4	1.8	1.4	1.8
Width of first gill opening	0.8	0.7	0.5	0.7
Width of third gill opening	0.9	0.7	0.4	0.7
Width of fifth gill opening	0.6	0.4	0.3	0.5
Distance between first gill openings	11.8	11.2	11.5	11.7
Distance between fifth gill openings	7.5	7.2	7.2	7.2
Clasper (post cloacal length)	18.0	5.7	0.0	0.0
Anterior pelvic lobe length	16.2	14.8	15.4	15.4
Posterior pelvic lobe length	15.7	14.0	12.4	14.8
Pelvic base width	4.3	5.0	4.2	4.9
Anterior pelvic lobe base width	2.7	2.0	2.3	2.3
Width across posterior pelvic lobes	9.4	7.9	6.6	9.0
Cloaca - caudal fin tip	43.8	48.5	45.8	51.4
Tail width (at insertion of pelvic fins)	1.4	1.0	1.0	1.0
Tail width (pelvic tips)	1.1	0.8	0.8	1.0
Tail height (pelvic tips)	0.8	0.8	0.8	0.9
Tail width (at midlength)	0.6	0.7	0.6	0.8
Tail width (at filament)	0.6	0.6	0.6	0.8