Rajella paucispinosa, Weigmann, Simon, Stehmann, Matthias F. W. & Thiel, Ralf, 2014

Weigmann, Simon, Stehmann, Matthias F. W. & Thiel, Ralf, 2014, Rajella paucispinosa n. sp., a new deep-water skate (Elasmobranchii, Rajidae) from the western Indian Ocean off South Mozambique, and a revised generic diagnosis, Zootaxa 3847 (3), pp. 359-387 : 362-371

Rajella paucispinosa n. sp.

(Sparsely-thorned skate)

Figs. 2–22 ; Tables 1–3

Holotype. ZMH 26000, almost adult male 471 mm TL fresh, 468 mm TL 70% ethanol preserved; RV ‘Vityaz’, cruise 17, station 2629, 23rd November 1988; 25°28’3”S, 35°28’7”E – 25°31’5”S, 35°25’9”E; 1230–1260 m depth, 29 m shrimp trawl, trawl # 26, on the bottom for 63 minutes, off South Mozambique.

Diagnosis. A small species of the genus Rajella with disc evenly inverse heart-shaped with broadly rounded outer corners and with body length to mid-vent shorter than tail length from mid-vent. Preorbital snout length 10.9% and distance between first gill slits 14.1% of TL. Orbits large, horizontal diameter 1.4 times interorbital width. Dorsal surface almost completely covered with dermal denticles; tail with large and coarse, densely set spinules as well as sharp, hooked thornlets that are not much larger than spinules. Only one small, blunt pre- and postorbital thorn on each side; one small nuchal thorn and one small right scapular thorn (left one not detectable, abraded); a median row of two small median posterior trunk and 15 small median tail thorns. When fresh, dorsal surface plain chalk white including orbits and ventral surface grayish-white. Bases of equal-sized and short but high dorsal fins confluent. Postdorsal tail section very short, with low epichordal caudal lobe which is confluent with second dorsal fin. Whitish lateral tail folds along posterior 45% of tail. Upper jaw tooth rows 31, pectoral fin radials 55–56. Clasper lacking external pseudosiphon; inner dorsal lobe with components slit, terminal bridge, and two clefts; inner ventral lobe with components shield, rhipidion, pent, sentinel, spike, and dike. Terminal clasper skeleton with four dorsal terminal cartilages, a terminal bridge, a ventral terminal, and two accessory terminal cartilages. Anterior cranial fontanelle with clear-cut contour all around and extending about one third into rostral shaft length. Scapulocoracoid subquadratic, rear corner sharply marked, large oval anterior fenestra without anterior bridge, one moderately large, oval postdorsal and postventral fenestra, respectively. Pelvic girdle with massive ischiopubic bar with nearly straight anterior and deeply concave posterior contour; prepelvic processes short, solid, conical, and somewhat inclined outwards, their length 1.9 times median thickness of ischiopubic bar.

Description ( Figs. 2–22 ). Detailed morphometrics and meristics are given in Table 1.

mm % TL

total length (TL) 468.0 100.0

disc, width 260.5 55.7, length 224.0 47.9

snout length, preorbital 51.0 10.9, preoral 59.0 12.6, prenasal 45.0 9.6

orbit, horizontal diameter 20.5 4.4

eyeball, horiz. diameter 13.0 2.8

interorbital width 14.2 3.0

spiracle length: slit 10.0 2.1

spiracle length: depression 12.6 2.7

interspiracular width 30.7 6.6

orbit + spiracle length 21.5 4.6

first dorsal fin (D1), height 15.8 3.4

, base length 22.5 4.8

second dorsal fin (D2), height 15.5 3.3

, base length 22.2 4.7

interdorsal space 0.0 0.0

caudal fin (C), base length 10.0 2.1

, height epichordal lobe 2.8 0.6

, height hypochordal lobe 0.0 0.0

, length hypochordal lobe 0.0 0.0

tail, postdorsal length 11.5 2.5

, height at pelvic-base-end 16.0 3.4

, width at pelvic-base-end 27.0 5.8

, height at pelvic-tips 12.0 2.6

, width at pelvic-tips 21.5 4.6

, height at D1-origin 5.0 1.1

, width at D1-origin 9.0 1.9

, lateral fold length 115.0 24.6

head length, ventrally 114.0 24.4, dorsally 79.0 16.9

mouth width 34.0 7.3

internarial width 34.3 7.3

nasal curtain, length 19.7 4.2

, width of each lobe 10.0 2.1

, space between lobes 17.6 3.8

gill slit length, 1st 5.5 1.2

, 3rd 7.1 1.5

, 5th 5.3 1.1

interspace first gill slits 66.2 14.1

.... ..continued on the next page External morphology ( Figs. 2–13 ). Disc evenly inverse heart-shaped, anterior margins of this almost adult male strongly undulated, i.e. concave at anterior sides of snout and at level of nape; pectoral apices very broadly rounded, continued evenly convex as posterior pectoral margins. Disc width 1.2 times disc length, disc length 4.4 times preorbital snout length and 3.8 times preoral snout length; axis of maximal disc width at 29% of TL and 60% of disc length ( Figs. 2–3 ). Dorsal head length 16.9% of TL. Snout short, tip bluntly rounded and not pronounced; snout angle about 102°; preorbital length 3.6 times interorbital width and 5.1 times in disc width ( Figs. 2 , 4 ). Orbits large, horizontal diameter 1.4 times interorbital width and 40% of preorbital snout length; spiracle aperture proper and depression lengths 49% and 61% of orbit horizontal diameter, respectively; interspiracular space 2.2 times interorbital width; 9 pseudobranchial folds in each spiracle ( Fig. 5 ). Tail solid, broadly depressed, gradually tapering to tip; length from mid-vent to tip 1.2 times body length from snout tip to mid-vent and 55% of TL; tail width to height at level of pelvic tips and at level of first dorsal-fin origin 1.8, respectively. Both dorsal fins of nearly equal size and shape, dorsal fins short but relatively high, their bases confluent; ratio base length to height 1.4, respectively; postdorsal tail section very short, only half of second dorsal-fin base length; epichordal caudal lobe low, confluent with second dorsal fin; whitish lateral tail folds along posterior 45% of tail ( Fig. 6 ).

Ventral head length 24% of TL and 3.3 times internarial width. Preoral snout length 1.5 times mouth width; mouth width 30% of ventral head length and equal to internarial space; distance between fifth gill slits 56% of distance between first gill slits, the latter 1.9 times internarial space ( Fig. 7 ). Rear margin of nasal flaps strongly fringed; outer edges of nasal curtain with a distinct lobelet, apices rounded, their outer margin and the rear margin of curtain deeply fringed; isthmus deeply arc-shaped ( Fig. 8 ). Jaws distinctly angled; 31 close-set parallel tooth rows each in upper and lower jaws; individual tooth with low, subcircular base and elongated, conically pointed cusp ( Fig. 8 ).

Pelvic-fin outer margin deeply notched, separating short thumb-like anterior lobe with bluntly rounded tip from elongated posterior lobe with broadly angled outer margin and bluntly pointed tip; length of posterior lobe 1.9 times length of anterior lobe ( Figs. 2–3 ). Claspers almost fully developed, maximum size obviously reached and all components developed but cartilages still less calcified than in claspers of adult male congeners; clasper postcloacal length 45% of tail length.

Squamation ( Figs. 4–6 , 9–11 ). Dorsal surface almost completely covered with dermal denticles, including the integument covering the eyeballs dorsally; only pectoral centers, anterior pelvic lobes, claspers, and a small patch posterior to spiracles smooth ( Fig. 5 ). Posterior pelvic lobe with a band of fine spinules across posterior third. Back and sides of tail very densely set with large, coarse spinules; both dorsal fins, caudal fin, and even inner lateral folds also densely set with coarse spinules ( Figs. 6 , 9 , 10 ).

Ventral side of disc, pelvic fins, and claspers smooth. Underside of tail densely set with very coarse spinules from about level pelvic tips to about level second dorsal-fin midbase; spinulation completely covering ventral tail in posterior half, but forwardly gradually tapering to a centrical band of spinulation in anterior half of tail with edges of tail smooth.

No thorns on snout, only one small, blunt pre- and postorbital thorn on each side ( Fig. 5 ); one small nuchal thorn and one small right scapular thorn (left one not detectable, abraded) ( Fig. 4 ); a median row of two small median posterior trunk and 15 small median tail thorns, from anterior to pelvic-fin origin to about two dorsal-fin base lengths anterior to first dorsal fin. Bases of all thorns ribbed. Sharp, hooked thornlets along posterior two thirds of tail to about origin of first dorsal fin, denser rearwards, in irregular lining on edges of upper tail but smaller than median thorns and not much larger than tail spinules ( Fig. 10 ).

A sickle-shaped field of strong, sharp malar thorns on each outer pectoral margin, terminating rearwards at level of spiracles ( Fig. 4 ). An elongated field of 2 longitudinal and 14–17 transverse rows of retractable alar thorns embedded in dermal pockets across outer pectoral corners ( Fig. 11 ).

Coloration. When fresh ( Figs. 12–13 ): dorsal side plain chalk white including orbits. Only posterior pectoral margins, outer two thirds of both pelvic lobes, and extreme clasper tips with a pale grayish-pink shade. Tail, lateral folds, dorsal fins, and caudal fin also white, but muddy bottom sediment fixed in spinulation at places.

Ventral side of disc and pelvic fins predominantly grayish-white; darker towards margins, especially from pectoral apices to pectoral axils. Nasal flaps, jaws, broad median interbranchial band, belly center, claspers, and tail white. Remains of dark grayish-brown mucus layer on outer pectorals, but pores not marked dark.

Color in preservative ( Figs. 2–3 ): dorsal ground color light beige; pectoral margins and anterior two thirds of claspers with a pinkish shade. Tail, lateral folds, dorsal fins, and caudal fins also light beige. Ventral side light beige with a pinkish shade except for belly center, anterior pelvic lobes, and tail which are beige without pinkish shade; pectoral margins and outer pelvic lobes darker.

Clasper external morphology ( Figs. 9 , 14 ). Claspers solid, evenly rod-shaped, terminal region not widened, distal part narrowing to spatulate, bluntly rounded tip; ventral glans lobe slightly broader than dorsal lobe and visible in dorsal view; pelvic fins fused to outer edges of claspers to somewhat anterior to apopyle ( Fig. 9 ). External pseudosiphon lacking. Inner dorsal lobe with a proximal slit (sl) and two deep, longitudinal clefts (cf), a smaller proximal and a larger distal one, separated from each other by terminal bridge (tb). Inner ventral lobe with a narrow, distinct shield (sh) along entire outer margin of lobe, with sharp cutting outer edge of free cartilage, proximal half of sh wider than distal half, distal third trough-like and with inner, nearly vertical wall forming component dike (dk); proximal inner half of sh forms a subrectangular, large protuberance that is covered by thin, smooth integument; lamellate pent (pe) along distal inner margin of shield and dike; a small, fan-shaped rhipidion (rh) with deeply porous surface in median inner area of lobe; two finger-like components covered by thick, fleshy tissue distally to rh, sentinel (st) and—underneath of it—spike (sk); hypopyle (hp) at proximal end of rh at about middle of glans ( Fig. 14 ).

Clasper skeleton ( Figs. 15–18 ): plate-like suboval beta cartilage (β) on head of axial cartilage (ax) moderately large, proximal half gradually tapering to bluntly rounded proximal tip, its length about one third of dorsal marginal cartilage (dm) length ( Figs. 15 , 16 ); narrowly strap-shaped and distally somewhat widening dm extending along proximal two thirds of clasper, its proximal end narrowing and bluntly pointed, not reaching proximal end of ax; dorsal terminal 1 cartilage (dt1) small and subrectangular, overlaying median part of dorsal terminal skeleton ( Fig. 16 ); dorsal terminal 2 cartilage (dt2) a subrectangular solid plate proximally, distal part bifurcated as a long, fingerlike inner process attached to ax and a broader outer part, broad and straight proximal edge connected to dm; dorsal terminal 3 cartilage (dt3) knife-blade-shaped, its proximal, bluntly rounded end attached to entire distal edge of notched outer distal part of dt2, its distal, pointed tip free underneath dorsal terminal 4; dorsal terminal 4 cartilage (dt4) inverse knife-blade-shaped, its proximal, pointed tip free and overlaying distal part of dt3, its distal tip loosely connected to tip of ax by ligament; dt3 and dt4 lie on top of each other along most of their lengths; separate terminal bridge cartilage (tb) small, rod-shaped, connecting dt3 with ax ( Fig. 17 ); ventral marginal cartilage (vm) plate-like solid, distinctly shorter than dm, its proximal, pointed end clearly not reaching proximal end of dm ( Figs. 15 , 16 ), its distal third widening, twisting to horizontal level and slightly curving around ax with distal inner margin ( Fig. 17 ); long ventral terminal cartilage (vt) slenderly J-shaped, its proximal part teardrop-shaped with broadly widened distal and pointed proximal part, its distal part slender with truncate tip and bluntly rounded inner median process; this median process, linking vt with at1, probably not yet fully developed in comparison with those of adult male congeners ( Fig. 18 ); Y-shaped accessory terminal 1 cartilage (at1) connected to distal and lateral end of vm with broadly concave indentation, its distal tip angled outwards with narrowly finger-like process forming st externally; narrowly rod-shaped accessory terminal 2 cartilage (at2) along inner side of at1, distal tip angled, narrowly spatulate, forming sk externally ( Fig. 17 ).

Cranium ( Fig. 19 ). Cranium shown by radiograph of almost adult male holotype (ZMH 26000), Table 2 provides cranial morphometrics measured from radiographs. Length of rostral shaft 49% of cranium length; rostral appendices not visible; maximal ethmoidal width 64% of cranium length and 4.1 times rostral base width; rostral base width 32% of rostral shaft length; minimal dorsal interorbital width 29% of maximal ethmoidal width; postnasal length of orbit region 28% of nasobasal length; length of otic region 33% of nasobasal length; maximal width of otic region 48% of maximal ethmoidal width. Both dorsal fontanelles separated by narrow cartilaginous bridge. Anterior fontanelle elongated triangular, with bluntly pointed tip and nearly straight transverse posterior edge, its length 27% of cranium length. Posterior fontanelle narrowly torch-shaped, with pointed anterior and posterior tips and with weak constriction at about two thirds of length; length of posterior fontanelle 24% of cranium length.

Scapulocoracoid ( Fig. 20 , A). Left scapulocoracoid shown by diagonal radiograph of holotype (ZMH 26000). Element subquadratic in lateral view, rear corner sharply marked, large oval anterior fenestra without anterior bridge, one large, oval postdorsal and one about equally large, oval postventral fenestra. Radiographs of dissected scapulocoracoids of nine congeners in lateral views shown in Figure 20 , B–J. Due to its apparent genus-specific morphology and due to the availability of only one single specimen, the scapulocoracoid of the holotype (ZMH 26000) of Rajella paucispinosa n. sp. was not dissected for obtaining morphometrics.

Pelvic girdle ( Fig. 21 ). Pelvic girdle shown by radiograph of holotype (ZMH 26000), Table 3 provides pelvic morphometrics measured from radiographs. Ischiopubic bar massive, with nearly straight anterior contour; iliac regions massive, with two foramina per side; posterior contour deeply concave arc-shaped as typical in adult male rajids. Prepelvic processes short, solid, conical, somewhat inclined outwards, and with bluntly rounded tip, their length 1.9 times median thickness of ischiopubic bar. Iliac processes long, massive, slenderly finger-like, and oriented anteriorly; transition to iliac regions well marked as blunt elevation. Axis of pelvic girdle maximal width anterior to rear contour of ischiopubic bar.

Skeletal meristics (from radiographs, Table 1, Fig. 22 ). Trunk vertebrae (Vtr): 25; predorsal tail vertebrae (Vprd): 66; interdorsal vertebrae (Vinterd): 8; postdorsal vertebrae (Vpostd, approximately): 22; pectoral radials, left/right: 56/55; pelvic radials, left/right: 1+19/1+20.

Size. A small skate reaching at least 471 mm TL. The male holotype is almost adult as its claspers have apparently reached their maximum size and all clasper components and alar thorns are developed. However, the cartilages are still not fully calcified and the median process of the ventral terminal cartilage is less developed than in claspers of adult male congeners. Therefore, the assumed maximum size of the species is about 500 mm.

Distribution ( Fig. 1 ). The holotype was caught in the western Indian Ocean off South Mozambique in 1230–1260 m depth. The new species represents the northernmost record of a Rajella specimen in the western Indian Ocean.

Etymology. The species name (lat. paucus = few, lat. spinosus = thorny) refers to the very reduced thorn pattern on the dorsal surface for a Rajella species.

Figures

FIGURE 1. Map of the southwestern Indian Ocean depicting the catch location of the holotype of Rajella paucispinosa n. sp. (white circle). Country abbreviation follows ISO 3166 - 1 (MZ = Mozambique).

FIGURE 2. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, dorsal view.

FIGURE 3. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, ventral view.

FIGURE 4. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, head in dorsal view.

FIGURE 5. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, orbit-spiracular region.

FIGURE 6. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, tail end in dorsal view.

FIGURE 7. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, head in ventral view.

FIGURE 8. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, mouth-nasal region.

FIGURE 9. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, claspers in dorsal view.

FIGURE 10. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, mid-section of tail in dorsal view.

FIGURE 11. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, alar thorn field on the left side.

FIGURE 12. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, fresh, dorsal view.

FIGURE 13. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, fresh, ventral view.

FIGURE 14. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, left glans clasper spread open. Abbreviations: cf = cleft, dk = dike, hp = hypopyle, pe = pent, rh = rhipidion, sh = shield, sk = spike, sl = slit, st = sentinel, tb = terminal bridge.

FIGURE 15. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, radiograph of claspers in dorsal view, right glans clasper spread open.

FIGURE 16. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, entire left clasper skeleton in dorsal view. Abbreviations: at 2 = accessory terminal 2, ax = axial, β = beta, dm = dorsal marginal, dt 1, dt 2, dt 4 = dorsal terminals 1, 2, 4, vm = ventral marginal.

FIGURE 17. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, left terminal clasper skeleton in (A) dorsal, (B) opened, and (C) ventral views (dorsal terminal 1 removed). Abbreviations: at 1 and at 2 = accessory terminals 1 and 2, ax = axial, dm = dorsal marginal, dt 2 to 4 = dorsal terminals 2 to 4, tb = terminal bridge, vm = ventral marginal, vt = ventral terminal. Dashed line in (C) indicates outline contour of vt cartilage to illustrate its position above other cartilages.

FIGURE 18. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, isolated left ventral terminal cartilage in (A) dorsal and (B) ventral views.

FIGURE 19. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, radiograph of cranium and snout in dorsal view.

FIGURE 20. Radiographs of dissected scapulocoracoids of 10 species of Rajella in lateral views except for that of R. paucispinosa n. sp. not dissected and in diagonal view. (A): R. paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, left scapulocoracoid, (B): R. barnardi, ZMH 105088, juvenile male, 494 mm TL, right scapulocoracoid (image reversed), (C): R. bathyphila, ZMH 111278, juvenile female, 270 mm TL, right scapulocoracoid (image reversed), (D): R. caudaspinosa, ZMH 105092, adult male, 544 mm TL, left scapulocoracoid, (E): R. dissimilis, paratype, ZMH 25259, juvenile female, 495 mm TL, left scapulocoracoid, (F): R. fyllae, ZMH 26020, adult male, 490 mm TL, left scapulocoracoid, (G): R. leoparda, ZMH 105099, juvenile male, 486 mm TL, left scapulocoracoid, (H): R. lintea, ZMH 25728, adolescent male, 894 mm TL, left scapulocoracoid, (I): R. ravidula, paratype, ZMH 25260, juvenile male, 605 mm TL, left scapulocoracoid, (J): R. sadowskii, paratype, ZMH 25264, juvenile female, 300 mm TL, left scapulocoracoid. Scale bars: 10 mm.

FIGURE 21. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, radiograph of pelvic girdle in dorsal view.

FIGURE 22. Rajella paucispinosa n. sp., holotype, ZMH 26000, almost adult male, 468 mm TL, radiograph in dorsal total view.

Tables

TABLE 2. Rajella paucispinosa n. sp., morphometrics of cranium of almost adult male holotype (ZMH 26000). Proportional values are expressed as percentages of nasobasal length (NBL).

	mm	% NBL
cranium TL	77.7	191.5
nasobasal length (NBL)	40.6	100.0
max. ethmoidal width	49.6	122.3
min. dorsal interorbital width	14.2	35.0
min. internasal width	7.8	19.2
max. width nasal apertures	20.1	49.6
min. ventral interorb./basal plate width	13.1	32.3
max. width otic region	24.0	59.2
max. width jugular	28.4	70.0
rostral shaft length	37.8	93.1
rostrum base width	12.2	30.0
postnasal length orbit region	11.2	27.7
length otic region	13.4	33.1
postoccipital length jugal arches	2.0	5.0
tip rostrum to tip anterior fontanelle	24.3	60.0
to end ant. fontanelle	45.3	111.5
to tip posterior fontanelle	46.5	114.6
to end post. fontanelle	65.5	161.5
to level ant. propterygia	18.7	46.2
to level max. ethmoidal width	44.0	108.5
to symphysis upper jaw	52.4	129.2
ant. fontanelle length	20.9	51.5
ant. fontanelle max. width	7.6	18.8
distance betw. ant. + post. fontanelles	1.2	3.1
post. fontanelle length	19.0	46.9
post. fontanelle min. width	1.9	4.6
post. fontanelle max. width anteriorly	2.8	6.9
post. fontanelle max. width posteriorly	3.7	9.2
angle post. edge nasal capsules, degrees	80

TABLE 3. Rajella paucispinosa n. sp., morphometrics of pelvic girdle of almost adult male holotype (ZMH 26000). Proportional values are expressed as percentages of pelvic girdle maximal width (PGW).

	mm	% PGW
maximal width shoulder girdle	56.2	142.9
pelvic girdle maximal width (PGW)	39.3	100.0
median transverse thickness	4.2	10.6
length prepelvic process (from level PGW)	8.0	20.2
length prepelvic proc. (from level ant. edge pelvis)	5.0	12.7
depth posterior arc (from level PGW)	7.4	18.9
depth posterior arc (from level post. edge pelvis)	6.4	16.2
iliac foramina number	2