Pavoraja mosaica, Last, Peter R. & Yearsley, Stephen Mallick And Gordon K., 2008
treatment provided by
Pavoraja mosaica sp. nov.
( Figs 1View FIGURE 1 c, 2 c, 10 –12, 13a –c, Tables 2, 4)
Pavoraja sp. D: Last and Stevens, 1994, Sharks and rays of Australia, pp 317, fig. 34.11, key fig. 37, pl. 46; Last and Compagno, 1999, Arhynchobatidae , softnose skates. In: Carpenter and Niem (eds), 1999, FAO species identification guide for fisheries purposes. The marine living resources of the Western Central Pacific, pp 1461, figs.
Holotype. CSIRO H 643 –02, 274 mm TL, adult male, north-east of Whitsunday Group, Queensland, 19 ° 38 ' S, 150 ° 33 ' E, 312–318 m, 15 Nov. 1985.
Paratypes. 10 specimens (83–279 mm TL): CSIRO H 595 –01, 268 mm TL, adult male; CSIRO H 595 – 0 3, 182 mm TL, juvenile male; CSIRO H 595 –04, 266 mm TL, female, off Townsville, Queensland, 18 ° 39 ' S, 148 °08' E, 300 m, 8 Dec. 1985; CSIRO H 643 –03, 234 mm TL, female, collected with holotype; CSIRO H 651 –01, 278 mm TL, female, south of Marion Reef, Queensland, 19 ° 44 ' S, 152 °06' E, 368–370 m, 23 Nov. 1985; CSIRO H 652 –01, 279 mm TL, female; CSIRO H 652 –02, 273 mm TL, female, east of Saumarez Reef, Queensland, 21 ° 56 ' S, 154 °00' E, 400–403 m, 20 Nov. 1985; CSIRO H 712 –01, 277 mm TL, female, Saumarez Reef, Queensland, 22 ° 14 ' S, 153 ° 31 ' E, 303–333 m, 19 Nov. 1985; CSIRO H 720 –09 (2 specimens), 83 mm TL, juvenile male; 139 mm TL, juvenile male, south of Saumarez Reef, Queensland, 23 ° 12 ' S, 153 ° 37 ' E, 399–405 m, 18 Nov. 1985.
Diagnosis. A species of Pavoraja with: a relatively short, narrow, depressed tail, length 51–53 % TL, height at pelvic-fin tips slightly more than half of width, width at midlength 1.6–1.9 % TL; a large nasal curtain, total width 7.1 –8.0% TL; widely spaced gill slits, width between first fill openings 12.4–14.1 % TL; orbital thorns small (often barely conspicuous), mostly 0–1 on posteromedial margin; interorbital, spiracular, nuchal, prenuchal and scapular thorns absent; thorns of tail series minute, lateral series poorly defined or absent; dorsal fins light brown with pale margins, confluent with pale epichordal lobe of caudal fin; tooth rows in lower jaw 37–47; predorsal caudal centra 72–76; interdorsal vertebrae 5–10; pectoral radials 71–74; dorsal surface brownish, covered with a dense pattern of irregular pale spots.
Description. Disc 1.12 in holotype (1.10–1.15 in paratypes) times as broad as long; maximum angle in front of spiracles 91 ° (98–101 °); anterior margin variable, convex, weakly biconcave or straight in females and immature males, mostly deeply concave opposite spiracles in adult males; posterior margin strongly convex; outer corners broadly rounded. Snout width at axis through anterior border of orbits 73 % (70–77 % in female paratypes) of distance from tip of snout to axil of pectoral fins. Pelvic-fin anterior margin 73 % (73– 83 %) of distance from origin of anterior lobe to posterior extremity of fin. Tail length 1.04 (0.97–1.04) times disc length; widths at midlength and at axils of pelvic fins 39 % (37–40 %) and 92 % (88–100 %) of orbit diameter respectively. Skin fold narrow, origin well defined, extending along ventrolateral surface from near pelvic-fin tip to near origin of hypochordal lobe of caudal fin; narrow initially, continuing evenly along predorsal tail, then widening behind second dorsal fin to equal height of epichordal lobe of caudal fin. Dorsal fins connected basally, interdorsal membrane often equal in height to epichordal fin lobe. Epichordal caudal-fin lobe connected to base of second dorsal fin (separated slightly in smallest juveniles CSIRO H 720 –09); base slightly shorter than bases of dorsal fins.
Preocular length 2.92 (2.77–3.10) times longer than orbit diameter; preoral length 2.53 (2.60–2.86) times internarial distance. Orbit diameter 1.33 (1.25–1.63) times interorbital distance; 2.00 (1.43 –2.00) times length of spiracles. Internarial distance 0.42 (0.39–0.42) in distance between first gill slits; 0.71 (0.71–0.83) in distance between fifth gill slits. Length of first gill slit 1.00 (1.00– 1.33) times length of fifth gill slit; 0.15 (0.11– 0.19) in mouth width.
Dorsal surfaces of disc, tail and posterior lobes of pelvic fins densely covered with fine denticles. Dorsal fins lightly denticulate (almost naked on smallest juveniles); claspers, anterior lobes of pelvic fins, skin folds on tail, caudal lobes and entire ventral surface naked. Orbit with 1–3 (mostly 2) thorns on anteromedial margin, 0–3 (mostly 0–1) on posteromedial margin, absent on medial margin. No prenuchal or nuchal thorns. Tail with 3 primary series of small to very small thorns; dorsolateral series poorly defined or absent (particularly in juveniles), extending variably along tail; medial series better defined, regular, originating near posterior pelvic-fin insertion, extending variably along tail; interdorsal thorns never present. Adult males with 2–3 irregular rows of small non-retractable alar thorns, not developed into dense patch of irregularly shaped thorns, clustered into pairs; malar thorns smaller, situated anterolaterally to alar thorns, extending anteriorly almost to greatest concavity of anterior margin of disc (usually just behind axis through posterior borders of spiracles).
Claspers moderately short, narrow ( Figs 13View FIGURE 13 a –c); pseudorhipidion continuing distally as fold of integument which fuses to inner wall of sentina; spur passing under slit proximally, not extending beyond glans, barely reaching posterior margin of rhipidion; rhipidion well developed, folded laterally along most of its length, running from proximal one-third to about distal one-third of glans, distal section lying over base of sentinel; sentinel rod-shaped, covered by thick integument; spike hidden within well-developed sentina; cleft medial and posterior to spur; axial cartilage curved laterally, moderately slender; dorsal marginal cartilage soft, little expanded distally, inner extension of distal margin initially expanded to a blade-like edge and then gradually thinning to a point; ventral marginal with truncated distal margin (joint unclear); dorsal terminal 1 and ventral terminal narrowly joined on ventral aspect of glans, forming sheath-like covering over central half of glans; dorsal terminal 1 membranous; ventral terminal mostly membranous, with thickened area immediately distal to proximal arm; lateral margin of dorsal terminal 2 smooth; terminal bridge absent; dorsal terminal 3 small; accessory terminal 1 with a laterally curved or S-shaped distal extension forming sentinel, extending just beyond spur.
Neurocranium of CSIRO H 652 –01 typical of genus; with one small accessory lateral cartilage beside each rostral appendix; foramina absent from rostral node; rostral shaft short, slightly less than length of basal fenestra; posterior fontanelle longer than anterior fontanelle.
Scapulocoracoid with 3 postventral foramina, anterior foramen largest (Fig. 2 c); 3 small condyles present on posterior part of neopterygial ridge.
Meristics (n= 5). Tooth rows in upper jaw 42 (37–47), in lower jaw 42 (37–47). Vertebral counts: monospondylous centra 30 (29–31), predorsal caudal centra 76 (72–75), interdorsal centra 5 (8–10), diplospondylous centra 103 (100–103), total centra 133 (129–134). Pectoral-fin counts: propterygial radials 31–33 (31– 35), mesopterygial radials 14–15 (13–15), metapterygial radials 27 (25–27), total radials 73–74 (71–74). Pelvic-fin counts: males 3 + 21 radials, females 3–5 + 18–21 radials.
Coloration. Preserved and live colour of adults similar, strongly ornamented with a dense reticulate pattern. Dorsal surface of disc, tail, posterior pelvic lobes, claspers and orbital membrane brownish with a mosaic of reticulations and small pale spots (variable in size, from about ¼ to ¾ spiracle width); preorbital snout and posterior margin of disc slightly paler; clasper apices dusky. Dorsal fins light brown with pale margins; anterior lobes of pelvic fins and epichordal lobe of caudal fin pale. Ventral surface mostly uniformly pale, somewhat translucent near outer corners of disc. Juveniles with spotted pattern reversed on dorsal surface, dense distribution of brown spots on a pale background, spots similar in size; 4–5 dark brownish black bands on tail, with 3 primary bands (also extending slightly onto ventral surface) more or less equally spaced, last band much broader than those anteriorly; first tail band situated about orbit diameter behind pelvic-fin tip; second tail band narrow; third tail band on midtail, about midway between first and last; last tail band broad, present below and extending onto dorsal fins; additional narrow and indistinct tail band sometimes present between third and last tail bands; ventral surfaces translucent.
Size. At least 279 mm TL and about 161 mm disc width. Males are mature by 268 mm TL. Smallest postnatal juvenile 83 mm TL.
Distribution. Known from the upper continental slope off Queensland, between Ingham (18 ° 39 ' S, 148 °08' E) and Yeppoon (23 ° 12 ' S, 153 ° 37 ' E), in depths of 300– 405 m.
Etymology. Derived from the Latin musaicus (an inlay of various colours and geometric patterns) in allusion to its striking dorsal coloration.
Comparisons. The dense pattern of pale, irregularly shaped spots and the sparse distribution of thorns on the disc distinguish this species from all other members of the genus. Within the genus, only P. n i t i d a has a dense pattern of pale spots but these are arranged quite differently. Pavoraja mosaica has more tooth rows in the lower jaw (37–47 vs. 31–36), more predorsal caudal centra (72–76 vs. 62–70), and slightly fewer interdorsal centra (5–10 vs. 8–10) than P. nitida .
Remarks. P. mosaica belongs to the North Eastern marine biogeographic province of Australia where it is found in the upper slope biome ( Last et al., 2005).
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