Notoraja sereti, White, William T., Last, Peter R. & Mana, Ralph R., 2017

White, William T., Last, Peter R. & Mana, Ralph R., 2017, A new species of velvet skate, Notoraja sereti n. sp. (Rajiformes: Arhynchobatidae) from Papua New Guinea, Zootaxa 4244 (2), pp. 219-230 : 220-229

Notoraja sereti n. sp.

Papuan Velvet Skate Figs 1–8 ; Table 1

Insentiraja subtilispinosa— Fricke et al., 2014: 15.

Holotype. NTUM 10067 , female 459 mm TL, southeast of Sek Island, Madang , Papua New Guinea, 5°07' S, 145°53' E, Papua Niugini cruise, R/ V Alis, station CP 3967, 980 m depth, 2 December 2012.

Paratypes. NTUM 10042 , female 458 mm TL, east of Sek Island, Madang , Papua New Guinea, 5°06' S, 145°53' E, Papua Niugini cruise, R/ V Alis, station CP3963, 960– 980 m depth, 30 November 2012 ; NTUM 10330 , adolescent male 363 mm TL, Astrolabe Bay , Madang, Papua New Guinea, 5°21' S, 145°53' E, Papua Niugini cruise, R/ V Alis, station CP4027, 800– 820 m depth, 14 December 2012 .

Diagnosis. A medium-size species of Notoraja with the following combination of characters: disc wider than long, width 47.1–50.3% TL, length 42.0–43.6% TL; short head (dorsal head length 15.2–16.2% TL; ventral head length 21.6–22.9% TL); relatively short snout (preorbital length 10.1–11.1% TL; ventral snout length 11.2–12.1% TL); interspiracular distance 5.3–5.9 TL, internasal distance 6.2–6.8% TL, preorbital length 2.4–3.0 times orbit length and 2.9–3.6 times interorbital; two dorsal fins, interdorsal space 1.1–1.9% TL; tail width at pelvic-fin axil 0.9-1.6 times its height; single, small preorbital thorn; dorsal and most of ventral surface of disc entirely velvety, covered with fine denticles; median disc and pelvic fins naked in adolescent male; anterior pelvic-fin lobe naked in females (skin naked or with sparse denticles ventrally on mid belly, chin, nasal curtain, and around cloaca); tail long and slender, entirely velvety and without thorn-like denticles; lateral tail folds moderately well developed; nasal lobes expanded, width of nasal curtain 7.9–8.3% TL; anterior pelvic-fin lobe slightly shorter or similar length to posterior lobe; dorsal and ventral surfaces greyish brown to dark bluish grey; total pectoral-fin radials 58–60; monospondylous centra 23–25, total diplospondylous centra 103–106, total centra 126–131.

Description. Disc heart-shaped, 1.17 (1.10–1.12) times as broad as long; maximum angle in front of spiracles 102° (96–100°); anterior margin nearly straight in females, weakly undulate in adolescent male paratype; apices broadly rounded; posterior margin moderately convex. Axis of greatest width 62% (61–64%) of disc length. Preorbital snout length 2.43 (2.98–2.99) times orbit length, 2.93 (3.28-3.58) times interorbital width; preoral snout length 1.76 (1.81–1.91) times internarial distance. Orbit diameter 1.21 (1.10–1.20) times interorbital distance, and 2.04 (1.70–1.78) times length of spiracles. Nasal lobes moderately expanded and rounded, posterior margin weakly fringed.

Mouth wide, its width more than 80 (80–81)% of maximum width of nasal curtain. Upper jaw weakly indented at symphysis; upper and lower jaws slightly convex on either side of symphysis. Teeth with relatively long, pointed cusps arranged in quincunx. Distance between first gill slits 1.82 (1.83) times larger than distance between nostrils; distance between fifth gill slits 1.22 (1.07) times larger than distance between nostrils.

Pelvic fins deeply incised with lobes connected by radials and membranes, anterior lobe moderately long, reaching to about posterior quarter of posterior lobe in females, finger-like with blunt tip (longer and more acute in adolescent male); posterior lobe with convex lateral margins, its posterior margin crenate due to extension of posterior radials. Tail narrowly oval at base, variably depressed over length; moderately convex dorsally, very weakly convex ventrally; tapering gradually posteriorly; tail width at axils of pelvic fins 1.69 (1.50–2.57) times width at its midlength, 2.29 (2.48–3.72) times its width at dorsal-fin origin respectively; length from rear of cloaca 1.45 (1.41–1.51) times distance from tip of snout to rear of cloaca; width at first dorsal-fin origin 2.13 (1.30–1.40) times its height; lateral skin folds originating at about anterior third of tail, extending to distal half of epichordal caudal-fin lobe; folds slightly broadening distally, but always narrower than tail width. Dorsal fins strongly raked, of similar shape and size; relatively short and rather low with convex anterior margins, straight or slightly convex posterior margins and broadly rounded rear tips; separated by a short interspace, 50% (36–60%) length of first dorsal-fin base. Epichordal caudal-fin lobe developed, separated by narrow interspace from and distinctly longer than second dorsal-fin base; hypochordal caudal lobe very low, originating near end of lateral fold, confluent with epichordal lobe.

holotype paratype paratype female subadult male female Total length (mm) 459 363 458 Disc width 50.3 47.1 47.8 Disc length (direct) 43.0 42.0 43.6 Snout to maximum width 26.6 25.7 27.9 Snout length (preorbital direct) 10.1 10.6 11.1 Snout to spiracle 15.0 15.0 14.8 Head (dorsal length) 15.2 16.0 16.2 Orbit diameter 4.2 3.6 3.7

Orbit and spiracle length 4.8 4.9 4.6

Spiracle length (main pore) 2.0 2.1 2.1

Distance between orbits 3.5 3.0 3.4

Distance between spiracles 5.8 5.3 5.9

Distance-snout to cloaca 40.9 39.8 41.0 Cloaca to D1 47.3 46.6 47.0 Cloaca to D2 51.7 51.1 50.4 Cloaca to caudal origin 55.4 55.7 53.8 Distance-cloaca to caudal-fin tip 59.4 60.1 58.0 Ventral snout length (pre upper jaw) 11.9 11.2 12.1 Prenasal length 8.7 8.2 8.9

Ventral head length (to fifth gill) 21.6 22.2 22.9 Mouth width 6.7 6.4 6.6

Distance between nostrils 6.8 6.2 6.3

Nasal curtain length 4.3 4.6 4.7

Nasal curtain (total width) 8.3 7.9 8.2

Nasal curtain (min width) 4.4 3.9 4.1

Nasal curtain (lobe width) 2.1 2.0 2.2

Width of first gill opening 1.5 1.3 1.4

Width of fifth gill opening 1.5 0.9 1.0

Distance between first gill openings 12.4 11.4 –

Distance between fifth gill openings 8.3 6.7 –

Clasper (post cloacal length) – 16.4 –

Length of anterior pelvic lobe 12.7 13.7 13.1 Length of posterior pelvic lobe 13.4 13.7 13.5

......continued on the next page holotype paratype paratype female subadult male female Pelvic base width 8.4 7.4 7.6 Tail at axil pelvic fins (width) 3.6 3.9 2.7 Tail at axil pelvic fins (height) 2.6 2.4 2.9 Tail at midlength (width) 2.1 1.5 1.8 Tail at midlength (height) 1.3 1.3 1.3 Tail at D1 origin (width) 1.6 1.0 1.1 Tail at 0 1 origin (height) 0.7 0.7 0.8 D1 base length 3.3 3.2 3.1 D1 height 1.5 1.2 1.5 D1 origin to caudal-fin tip 12.3 13.8 12.0 D2 origin to caudal-fin tip 7.7 8.9 8.2 Caudal-fin length 4.4 4.6 4.0 lnterdorsal distance 1.7 1.9 1.1 Dorsal surface of disc velvety, entirely covered with fine, densely spaced, dermal denticles; denticles bristlelike, erect, with almost straight pointed crowns. Ventral surface of disc similarly covered on most surfaces, except median disc (oronasal region, branchial region and belly, Fig. 10 b) and entire pelvic fins of adolescent male naked; anterior pelvic-fin lobe naked in females (skin naked or with sparse denticles ventrally on mid belly, chin, nasal curtain, and around cloaca). A single, small, but conspicuous preorbital thorn present; no other orbital thorns or thorns on disc of types. Tail velvety, densely covered with fine, dermal denticles; no enlarged thorns; a few small, variably spaced thornlets on midline of tail but these very small, barely taller than largest denticles adjacent.

No adult males available; adolescent male paratype with relatively long and very slender clasper, post cloacal length 16.4% TL.

Tooth rows in upper jaw 43 (39–41); lower jaw 39 (37). Pectoral propterygial radials 27 (26–27); mesopterygial radials 11 (10-11); metapterygial radials 20–21 (22-23); total radials 58–59 (58–60). Monospondylous centra 25 (23–24); diplospondylous predorsal centra 70 (66–71); predorsal centra 95 (90–94); post-first dorsal-fin origin centra 36 (32–38); total diplospondylous centra 106 (103–104); total centra 131 (126– 128).

Colour. Holotype and female paratype (fresh): Dorsal surface uniformly medium brown, slightly paler above orbits and at pectoral insertions; anterior third of tail darker brown with a narrow, darker brownish median stripe originating anterior to dark brown marking (about level with pelvic-fin insertions); dorsal and caudal fins medium brown with darker edges. Ventral surface of disc similar in colour to dorsal disc; anterior third of tail slightly darker brown. When preserved, dorsal coloration slightly paler brown; dark brown dorsal midline obvious on anterior tail, but darker anterior marking on tail more obvious. Adolescent male paratype (fresh): dorsal surface bluish grey with paler anterior pelvic-fin lobes; most of dorsal midline and tail distinctly paler except near tip. When preserved, dorsal coloration dark brown, darkest distally near disc apices; dark midline on anterior tail obvious; dark marking on anterior tail less obvious; ventral surface of disc and tail dark, slightly paler than dorsal surface in adolescent male but similar in females; adolescent male translucent on belly and branchial region, noticeably darker near disc margin.

Size. Known from the three type specimens consisting of two females (459 and 458 mm TL) and an adolescent male (363 mm TL). The clasper of the adolescent male (postcloacal length 16.4% TL) was possibly about threequarters of full extension (maximum length of adult claspers of N. sapphira and N. azurea 22.5% and 22.6% TL respectively). Based on the adolescent male size, the females are most likely adults.

Distribution. Off Madang, Papua New Guinea at depths of 800–980 m ( Fig. 9 ).

Etymology. Named after the highly respected French ichthyologist, Dr. Bernard Séret, who has contributed greatly to the taxonomy of sharks and rays, and in particular to our knowledge of skates of the genus Notoraja . English name: Papuan Velvet Skate.

Comparisons. The new species is assigned to the genus Notoraja which is particularly diverse in this part of the Indo–Pacific. The dorsal and most of the ventral surfaces of Notoraja sereti are entirely covered with fine, densely spaced, dermal denticles which is shared by the velcro skates, N. alisae Séret & Last, 2012 ; N. fijiensis Séret & Last, 2012 ; N. inusitata Séret & Last, 2012 ; and N. longiventralis Séret & Last, 2012 . In contrast, the remaining species in the genus, i.e. N. azurea McEachran & Last, 2008 ; N. hirticauda Last & McEachran, 2006 ; N. lira McEachran & Last, 2008 ; N. ochroderma McEachran & Last, 1994 ; N. sapphira Séret & Last, 2009 ; N. sticta McEachran & Last, 2008 ; and N. tobitukai ( Hiyama, 1940) , all have a smooth ventral surface entirely devoid of denticles. However, it should be noted that the adolescent male has a poorer coverage of denticles on the ventral surface than the larger females (see e.g. Fig. 10 a), and it is likely that denticle coverage on the ventral surface is size related. Juveniles were unavailable for study but they are likely to be less well spinulated (possibly naked) than adults and adolescents.

Notoraja sereti differs from N. alisae , N. fijiensis , N. inusitata and N. longiventralis in having a shorter snout (preorbital length 10.1–11.1 vs. 11.5–14.5% TL, prenasal length 8.2–8.9 vs. 9.8–12.1% TL); a shorter head (dorsal head length 15.2–16.2 vs. 17.1–19.3% TL, ventral head length 21.6–22.9 vs. 22.9–25.9% TL); fewer pectoral radials (total radials 58–60 vs. 61–74) and fewer vertebral centra (predorsal diplospondylous centra 66–71 vs. 72– 82; predorsal centra 90–95 vs. 98–107; total centra 126–131 vs. 135–152). It differs from N. alisae , N. inusitata and N. longiventralis in disc length (42.0–43.6 vs. 43.8–47.8% TL). It differs from N. alisae , N. fijiensis and N. inusitata in having more widely separated dorsal fins (interdorsal space 1.1–1.9 vs. 0.5–0.9% TL).

Notoraja sereti further differs from N. alisae in the following characters: disc width 47.1–50.3 vs. 50.9–55.5% TL; orbit and spiracle length 4.6–4.9 vs. 5.1–5.5% TL; and distance between spiracles 5.3–5.9 vs. 6.2–6.7% TL. It further differs from N. fijiensis in the following characters: ventral surface dark (vs. creamy white); snout to spiracle 14.8–15.0 vs. 15.5–16.2% TL; distance from snout to cloaca 39.8–41.0 vs. 35.0–38.9% TL; ventral snout length 11.2–12.1 vs. 13.2–14.6% TL; and a wider mouth (mouth width 6.4–6.7 vs. 5.7–6.2% TL). Notoraja sereti further differs from N. inusitata in the following characters: snout to spiracle 14.8–15.0 vs. 17.3% TL; nasal curtain total width 7.9–8.3 vs. 7.2% TL; and fewer radials on the mesopterygium 10–11 vs. 16. It further differs from N. longiventralis in having a much shorter anterior pelvic-fin lobe (its length 12.7–13.7 vs. 14.8–15.0% TL) and shorter distance from the cloaca to the first dorsal fin (46.6–47.3 vs. 45.1–45.9% TL).

The new species of arhynchobatid skate is distinguishable from members of the closely related genus Insentiraja in having numerous small denticles on the ventral surface (vs. ventral surface smooth) and the skin on both dorsal and ventral surfaces not loose and flabby (vs. skin noticeably loose and flabby). It also differs from members of another closely-related genus Brochiraja in lacking a bifurcate thorn on the snout tip.

Figures

FIGURE 1 Dorsal view of the holotype of Notoraja sereti n. sp. (NTUM 10067, female 459 mm TL) immediately postcapture.

FIGURE 2. Preserved holotype of Notoraja sereti n. sp. (NTUM 10067, female 459 mm TL): (A) dorsal view; (B) ventral view.

FIGURE 3. Dorsal view of the adolescent male paratype of Notoraja sereti n. sp. (NTUM 10330, 363 mm TL) immediately post-capture.

FIGURE 4. Dorsal view of the adolescent male paratype of Notoraja sereti n. sp. (NTUM 10330, 363 mm TL) after preservation.

FIGURE 5. Dorsal head of Notoraja sereti n. sp.: (A) holotype, NTUM 10067, female 459 mm TL; (B) paratype, NTUM 10330, subadult male 363 mm TL.

FIGURE 6. Oronasal region of the holotype of Notoraja sereti n. sp. (NTUM 10067, female 459 mm TL).

FIGURE 7. Dorsal view of the tail tip of the holotype of Notoraja sereti n. sp. (NTUM 10067, female 459 mm TL).

FIGURE 8. Dermal denticles of the holotype of Notoraja sereti n. sp. (NTUM 10067, female 459 mm TL): (A) dorsal surface; (B) ventral surface).

FIGURE 9. Map showing the capture locations of the type specimens of Notoraja sereti n. sp. (red star denotes holotype, yellow circles paratypes) in Astrolabe Bay, Papua New Guinea. Inset map shows location of main map in context of the whole country (Image © NASA, TerraMetrics, Google Earth).

FIGURE 10. Denticle pattern in Notoraja sereti n. sp. highlighting areas lacking denticles: (A) ventral head of adolescent male paratype (NTUM 10330, 363 mm TL); (B) belly of female paratype (NTUM 10042, 458 mm TL).