Brochiraja vittacauda, Last, Peter R. & Séret, Bernard, 2012

Last, Peter R. & Séret, Bernard, 2012, Two new softnose skates of the genus Brochiraja (Rajoidei: Arhynchobatidae) from the deepwater slopes and banks of the Norfolk Ridge (South-West Pacific), Zootaxa 3155, pp. 47-64 : 56-61

Brochiraja vittacauda sp. nov.

( Figs 8–14 ; Table 1 )

Rajidae n. gen. sp. E: Last in Williams et al., 2006, Appendix 6, p. 1 (field identification, listed); Appendix 8: p. 6 (2 photos n° 37031808)

Holotype. NMNZ P. 39563, adult male 719 mm TL, West Norfolk Ridge, 34°18.9'S, 168°24.3’E, 809–857 m depth, RV Tangaroa NORFANZ TAN 0308/147, bottom trawl, 3 Jun 2003.

Paratype. Single specimen from the Tasman Sea. NMNZ P. 42691, juvenile male 360 mm TL, West Norfolk Ridge, 33º40.8'S, 167º 50.5' E, 629–973 m depth, F.V. Seamount Explorer, bottom trawl, 13 Mar 2006.

Diagnosis. A large species of Brochiraja distinguished by the following combination of characters: long tail, 1.2–1.4 times disc length, 2.3–2.8 times ventral head length, 4.7–5.8 times snout length; orbit moderately large, 2.8–3.1 in preorbital snout length; tail slender but with relatively broad conical base, evenly tapering to mid-length of tail, width at pelvic-fin insertions 2.0–2.5 times width at midlength; anterior lobe of pelvic fin broadly spatulate; central dorsal disc with fine denticles, otherwise naked apart from enlarged, thorn-like denticles around margin of snout and near alar patch in adult males; tail with mediodorsal row of about 36–51 hooked thorns and small spiny denticles concentrated on its dorsolateral surface; single preorbital thorn, 0–1 midorbital thorns, 1–3 postorbital thorns; snout length 2.6–3.7 times distance from snout tip to bifurcate rostral thorn; calcified rostral shaft short; ventral disc and tail naked; alar thorns in a broad patch, flanked by smaller malar thorns; additional separate patch of malar thorns on snout forward of mid-eye; lateral skin fold very broad posteriorly, originating well forward, beside pelvic-fin inner margins in adult male; dorsal surface dark violet, ventral surface brownish blue, darker than dorsal surface; no beard-like patch beneath mouth; rows of faint pale-edged pores on ventral surface; tail tip white; nuchal pore patch distinct; total pectoral radials 76–77; predorsal vertebrae 112–114; 40–44 tooth rows in upper jaw.

Description. Disc heart shaped to suboval, 1.03 in adult male holotype (1.09 in juvenile male paratype) times as broad as long; maximum angle in front of spiracles 89° (112°); anterior margin weakly double concave, almost straight opposite spiracles in paratype, apex and rear tip broadly rounded, posterior margin convex; axis of greatest width about 56% (53%) of disc length. Head moderately elongate, 18.8% (16.7%) TL; snout angular, broader in paratype, preorbital snout length 3.12 (2.78) times orbit diameter, 3.68 (3.15) times interorbital distance; preoral snout length 1.96 (1.69) times internarial distance. Snout tip lobe like, forming small, subtriangular, fleshy process in paratype; process distinctly demarcated from anterior profile of disc. Orbit large, elevated (more so in paratype), diameter 1.18 (1.13) times interorbital distance. Spiracle of moderate size; main pore covering most of spiracular depression, its length of 2.09 (2.25) in orbit diameter; its anteriormost extension slightly forward of hind margin of eye. Nostril suboval (distorted in both types), small, with about 20 lamellae in holotype; anterior nasal flap expanded laterally, lobe like, partly concealed by nasal curtain anteriorly, weakly tubular along its lateral margin, posterior margin well concealed beneath nasal curtain. Nasal curtain well developed, broader than long; its lateral margin concave anteriorly (wrapping around anterior lobe), expanded medially, then broadly rounded posterolaterally; labial margin poorly fringed; internarial distance 1.60 (1.78) in distance between first gill slits, 0.94 (1.03) in distance between fifth gill slits. Upper and lower jaws strongly arched at symphysis, much less so in paratype. Teeth small with long, pointed cusps; cusps longest near middle of jaws; cusps at symphysis of upper jaw slightly smaller than those adjacent; cusps short, knob like near jaw angle; in upper jaw, cusps directly posterolaterally, in lower jaw directed anterolaterally. In paratype. quincuncial with elevated, crowns; crowns plate-like, suboval to quadrangular, with short blunt cusps; cusps posteriorly directed, best developed lingually.

Pelvic fin deeply incised; anterior lobe fleshy, relatively elongate, spatulate, broad along its entire length with a broadly rounded apex, inner margin not incised; posterior lobe relatively short, with weakly incised and weakly convex lateral margin, free rear tip forming a narrower angle than fin apex, inner margin almost straight, slightly convex in paratype; length of anterior lobe 0.78 (0.87) times length of posterior lobe. Tail slender at base, tapering evenly and very gradually posteriorly, pointed at its tip in paratype; width to height ratios variable, width at insertions of pelvic fins 2.01 (2.46) times width at midlength of tail and 1.97 (3.21) times width at first dorsal fin origin respectively; length from rear of cloaca 1.37 (1.62) times distance from tip of snout to rear of cloaca; in cross section, holotype relatively more depressed than paratype, dorsal surface convex, ventral surface convex anteriorly, becoming almost flat posteriorly; weak median groove along tail on ventral surface (less obvious in paratype); width 1.34 (1.59) times height at insertion of pelvic fin, 2.02 (1.46) times height at first dorsal fin origin. Lateral skin fold very well developed; originating beside inner margin of pelvic fin; terminating beyond tip of tail in holotype, but abruptly near mid-base of epichordal lobe in paratype; very broad distally, particularly in holotype, maximum width on each side almost equivalent to height of first dorsal fin, width on each side of paratype equivalent to height of epichordal lobe of caudal fin. Dorsal fins small, short-based, low, located near tail tip; first dorsal fin slightly smaller than second, strongly raked, its apex almost over its insertion, first dorsal-fin height 2.11 (2.30) times in its base length; second dorsal fin similar in shape, also strongly raked, posterior margin subequal in length to inner margin; fin bases clearly separated, rear tip of first dorsal fin overlapping second dorsal-fin origin, interdorsal distance 2.26 (1.73) times in length of first dorsal-fin base. Epichordal caudal-fin lobe small in holotype; relatively well developed in paratype, more than half height of first dorsal fin; distance from second dorsal-fin base subequal to interdorsal distance; hypochordal caudal lobe absent, rudimentary in paratype.

Dorsal surface of disc and pelvic fins mostly naked, except for minor granulations and orbital, rostral, alar, malar and tail thorns; widely spaced, smaller denticles on mid disc extending into tail, best developed dorsolaterally and continuing to tail tip in about 3 rows below dorsal fins; ventral surface entirely naked. In paratype, dorsal surface naked, except for a few thorns and a band of minute, widely spaced denticles extending along mid-disc from nuchal region to tail; band broadest over scapular region; band divided above cloaca into two narrower bands, each extending along lateral and dorsolateral surfaces of tail to second dorsal fin; dorsal tail beside median thorns naked; sparse covering of denticles on dorsal fins and epichordal lobe of caudal fin; ventral surfaces of disc and tail naked. Denticles unicuspid, with partly embedded, mostly quadrate bases; cusps extremely short, slender, pungent, mostly strongly recurved.

Thorns confined to mid-snout, orbits, midline of tail, and as well-developed alar and malar patches in adult male holotype. Bifurcated rostral thorn enlarged in juvenile paratype (anterior length ca 3.3 mm), broad based with prominent, strongly oblique, bifurcated crown; less obvious in holotype; forward on snout, its distance from snout tip about 2.57 (3.68) in preorbital snout length. Paratype with two large and prominent, broad-based orbital thorns with recurved tips; one preorbital and one postorbital thorn aligned with anterior and posterior orbital margins respectively; holotype with additional 1–2 postorbital thorns and one smaller median thorn, all positioned around orbital margin; 36 thorns on dorsal midline of tail in paratype, enlarged (up to 4.3 mm anterior length), in a single, closely spaced, regular row; bases of thorns compressed and subtriangular, distal half slender, recurved; integument of ventral surface relatively thick, fleshy; median series persistent in adult, 51 thorns in an almost regular row, size variable, notably smaller near dorsal fins; no interdorsal thorns. Alar thorn patch of mature male well developed; non-retractable, posteromedially directed thorns in 2–4 longitudinal rows on mid-outer pectoral fin; thorns flanked laterally by a broad band of slightly smaller, more posteriorly directed malar thorns that extend forward in a narrow band along disc margin to spiracle; additional pair of broad patches of malar thorns on snout forward of orbits.

Rostral cartilage (from radiograph) narrow basally, calcified component elongate, extending anteriorly beyond rostral thorn; rostral appendices well developed, visible on radiograph; anterior fontanelle broadly flask shaped, extending onto rostral cartilage well anterior to leading edge of nasal capsules; propterygium of pectoral girdle not reaching rostral node; lateral prepelvic processes of pelvic girdle moderately elongate. Claspers slender, elongate, postcloacal length 20.9% TL when mature; glans little expanded, bluntly pointed distally, distal aperture moderately large; configuration similar to other members of the genus as in Last & McEachran (2006); tip of ventral marginal cartilage recurved, spatulate.

Tooth rows in upper jaw 44 (40, n=1); lower jaw 40 (38). Pectoral-fin propterygial radials 35 (35, n=1); mesopterygial radials 14 (13–14); metapterygial radials 28 (28); total radials 77 (76). Monospondylous centra 28 (28, n=1); predorsal caudal centra 84 (86); predorsal centra 112 (114); total centra about 142 (139).

Coloration. In holotype (when fresh), dorsal surface mostly dark violet, and outer disc, pelvic fins and tail reddish brown, orbital membranes similar to adjacent disc; ventral surface slightly darker brownish blue, sensory pores paler, rows evident; jaws, most of second dorsal fin, caudal fin, half of dorsal clasper, distal ventral surface of anterior pelvic-fin lobe, ventral tip of tail, margin of first dorsal fin, and clasper white; outer half of both anterior pelvic lobes covered with unusually thick, white mucous; preserved coloration similar, bluish dorsally, darker brownish ventrally, whitish areas remaining obvious; enlarged denticles and thorns white, strongly contrasted with rest of disc. In juvenile paratype (when fresh), dorsal surface of disc and tail almost uniformly dark blue; iris and thorns pale, strongly contrasted with base colour; first dorsal fin white basally, dark distally; second dorsal fin and epichordal lob of caudal almost uniformly white; ventral surface of disc bluish brown (slightly darker than dorsal surface); ventral pores not obvious, although some pale pores on anterior head and on anterior disc; anterior nasal flap, mouth, gill-slit anterior membranes, clasper tips, and origin and subdorsal length of tail whitish.

Size. Males reach at least 719 mm TL; no information available for females.

Distribution. Known from small section of the West Norfolk Ridge (ca 33º40– 34°18' S, 167º 50– 168 °24’ E) at 629–973 m depth ( Fig. 11 ).

Etymology. A combination of the Latin vitta (ribbon) and cauda (tail) with reference to the appearance of the tail due to its unusually broad lateral skin folds that terminating near its tip. Vernacular name: Ribbontail Skate.

Comparisons. Brochiraja vittacauda is either sympatric or parapatric with B. aenigma and B. heuresa on the Norfolk Ridge. It is a much larger skate than B. heuresa (adult males to about 72 cm vs. 36–38 cm TL) and is probably larger than B. aenigma . The dorsal surface is less spinulose than in either of these species (denticles concentrated near mid-disc rather than being distributed all over), and well developed thorns are present on in pre and postorbit (rather than being reduced or absent). The pectoral-fin radial and vertebral counts are high as in B. aenigma (total pectoral radials 76–77 vs. 73–74 and predorsal centra 112–114 vs. 115 in B. aenigma ; total pectoral radials 58–63 and predorsal centra 88–100 in B. heuresa ), but the disc is more angular and the tooth row count higher (40–44 vs. about 30 rows in upper jaw) than B. aenigma .

Of the New Zealand Brochiraja , B. vittacauda is most similar to B. leviveneta but has a broader, more spatulate, anterior pelvic-fin lobe, much broader lateral skin fold, higher pectoral-fin radial and vertebral counts (total pectoral radials 76–77 vs. 64–69 and predorsal centra 112–114 vs. 95–100), better developed alar and malar thorns in adult males, and reaches a larger adult size (adult males to about 72 cm vs. 36–38 cm TL).

Figures

FIGURE 8. Brochiraja vittacauda sp. nov., adult male holotype (NMNZ P 39563, 719 mm TL, fresh): A, dorsal surface; B, ventral surface.

FIGURE 9. Brochiraja vittacauda sp. nov., adult male holotype (NMNZ P 39563, 719 mm TL, preserved) showing snout, orbito-spiracular and nuchal regions.

FIGURE 10. Ventral view of the head of Brochiraja vittacauda sp. nov.: adult male holotype (NMNZ P 39563, 719 mm TL, preserved) showing the oronasal region and tooth bands.

FIGURE 11. Radiograph of the head of Brochiraja vittacauda sp. nov., adult male holotype (NMNZ P 39563, 719 mm TL).

FIGURE 12. Thorns at tail midlength of Brochiraja vittacauda sp. nov.: A, dorsal and B, lateral views of adult male holotype (NMNZ P 39563, 719 mm TL, preserved).

FIGURE 13. Lateral view of the dorsal and caudal fins of Brochiraja vittacauda sp. nov., adult male holotype (NMNZ P 39563, 719 mm TL, preserved).

FIGURE 14. Dorsal view of bifurcated rostral thorns of A, Brochiraja heuresa sp. nov. (female paratype, CSIRO H 6091 – 01, 364 mm TL, preserved) and B, B. vittacauda sp. nov. (adult male holotype, NMNZ P 39563, 719 mm TL, preserved).