Notoraja hirticauda, Last & McEachran, 2006

Last, Peter R. & McEachran, John D., 2006, Notoraja hirticauda, a new species of skate (Chondrichthyes: Rajoidei) from the south-eastern Indian Ocean, Memoirs of Museum Victoria 63 (1), pp. 65-75 : 66-75

Notoraja hirticauda sp. nov.

Figures 1–8 , Tables 1 –3

Notoraja sp. C — Last and Stevens, 1994: 312, figs 33, 34.5, Pl 50

(all fig. captions incorrect, as N. sp B).

Material examined. Holotype. Australia: CSIRO H1816–02 , 446 mm TL, mature male, west of Shark Bay , Western Australia, 26°36'S, 112°09'E, 760 m, 28 December 1989, RV “Akebono Maru”, sta. 41.

Paratypes (n=8): Australia: CSIRO CA 2820, 312 mm TL, female , CSIRO CA 2821, 264 mm TL, female, north of Nickol Bay , Western Australia, 18°38'S, 116°54'E, 600 m, 7 Apr 1982 , FRV “ Soela ”, Cr. 2, sta. 30 ; CSIRO CA 2822, 241 mm TL, female, CSIRO CA 2823, 277 mm TL, female, north of Nickol Bay , Western Australia, 18°41'S, 116°45'E, 596 m, 6 Apr 1982 , FRV “ Soela ”, Cr. 2, sta. 28 ; CSIRO CA 2824, 361 mm TL, immature male, north of Nickol Bay , Western Australia, 18°43'S, 116°33'E, 612 m, 7 Apr 1982 , FRV “ Soela ”, Cr. 2, sta. 29 ; CSIRO H1816-03 , 448 mm TL, mature male, captured with holotype ; CSIRO H1822-01 , 372 mm TL, female, west of Shark Bay , Western Australia, 26°44'S, 112°19'E, 735 m, 28 Dec 1989 , RV “ Akebono Maru ”, sta. 40 ; CSIRO H2574-06 , 428 mm TL, female, west of Freycinet Estuary , Western Australia, 26°38'S, 112°30'E, 500 m, 30 Jan 1991 , FRV “ Southern Surveyor ”, Cr. 1, sta. 37 .

Diagnosis. A small species of Notoraja with the following combination of characteristics: preoral snout 13.5–15.2% TL; preorbital snout 12.3–13.8% TL; mutiple irregular rows of small, bristle-like thorns and large dermal denticles present on both surfaces of tail; single preorbital thorn present; no oronasal pits; rostral cartilage about 1.25 in nasobasal length; rostral appendices about 62% of nasobasal length, subtriangular in cross-section posteriorly and evenly abutting rostral shaft; pectoral radials 61–66; trunk vertebrae 24–27, precaudal tail vertebrae 71–76; and both surfaces of body pale.

Description. Disc heart-shaped, 1.11 times as broad as long in holotype (1.11–1.16 times in paratypes); maximum angle in front of spiracles 73–75° in adult males, 93–97° in females and juveniles; anterior margin initially straight, slightly more convex in females and immatures, moderately concave opposite spiracles in mature male holotype; posterior margin and corners broadly convex (figs 1, 2). Snout to axis of greatest width 61.5% (57.7–60.9%) of disc length. Snout tip with prominent fleshy and laterally flattened apical process; process rather broad-based and almost continuous with anterior profile of disc in mature males, more lobe-like in immatures and adult females. Pelvic fins deeply incised, anterior lobe moderately long, narrow at base and tapering to blunt point; posterior lobe relatively short, with strongly convex lateral margins; anterior lobe length 95.7% (93–113%) of posterior lobe. Tail narrow at base, tapering gradually posteriorly, very slender toward tip; moderately depressed over length, width 1.42 (1.44–1.72) times height at axil of pelvic fin; slightly convex on ventral surface; lateral skin folds originating well behind posterior pelvic-fin lobes, extending to below mid-length of epichordal caudal-fin lobe and broadening distally (only slightly narrower than height of epichordal lobe); length of tail from rear of cloaca 1.40 (1.40–1.50) times distance from tip of snout to rear of cloaca; predorsal tail length 78.1% (78.2–81.4%) of tail length; width at midlength of tail 2.06 (1.99–2.72) in orbit diameter; width at axils of pelvic fins 0.80 (0.85–1.00) in orbit diameter. Dorsal fins of similar shape and size; rather short and moderately tall with evenly convex anterior margin; posterior margin straight or slightly convex; tip pointed or acutely rounded; fins separated by short interspace.Epichordal caudal-fin lobe relatively well developed, separated by short interspace from and distinctly longer than 2nd dorsal-fin base; hypochordal caudal lobe very low, originating near end of lateral fold, not confluent with epichordal lobe. Preorbital snout length 4.02 (3.15–3.50 in females and immatures) times orbit diameter; preoral snout length 2.29 (1.98–2.35) times internarial distance. Orbit diameter 1.17 (1.11–1.45) times interorbital distance; 1.87 (2.02–3.08) times length of spiracles. Lateral nasal fold expanded slightly, with weak triangular process along lateral margin, posterior margin smooth or with a weak fringe; nasal curtain moderately well developed, broadly rounded and weakly fringed (often hardly detectable) along posterior margin. Oronasal pits absent. Upper and lower jaws slightly arched on either side of symphysis; upper jaw of holotype indented at symphysis, not indented in females and immatures. Teeth in 36 (35–40) series in upper jaw, 34 (32–39) series in lower jaw; plate-like with short cusps in females, cusps acutely pointed in males, arranged quincuncially. Distance between 1st gill slits 1.72 (1.63–1.91) times distance between nostrils; distance between 5th gill slits 1.07 (1.04–1.27) times distance between nostrils; length of 1st gill slit 6.7 (4.7–8.4) times mouth width.

Dorsal surface of disc, posterior lobe of pelvic fin, dorsal fins, epichordal lobe of caudal fin, and lateral skin folds densely end peri fig.4a ja

X oc fig.4c scp

ab

msc

mtc

obf fig.6b

sl

cf

dtr

tb

dtr1

fig.8a

vmg

atr2 fig.8b fig.8c covered with fine, more or less evenly spaced dermal denticles; thorns (fig. 3) small, delicate, confined to tail and preorbit, and alar regions of mature males. Denticle cusps on disc very slender, erect and slightly recurved; bases quadriradial, radii arranged more or less at right angles, anterior radius generally shortest (sometimes barely detectable). Both surfaces of tail densely covered with denticles and small, bristle-like thorns; thorns variable in size, scattered, interspersed with denticles; median thorns in an almost linear series, other thorns distributed randomly or in irregular series; largest thorns long-based, somewhat compressed, sharply pointed distally, upright and triangular or with narrow recurved tips; most numerous dorsally on centre of tail; thorns on ventral surface of tail generally smaller than those dorsally but much larger than denticles of disc. Single, rather short preorbital thorn present. Alar thorns strongly recurved and directed postero-medially, central group in indistinct rows and merging with a cluster of smaller thorns near anterior outer margin of pectoral fin; holotype with about 5–6 central rows, each with 1–4 thorns (mature male paratype with about 9–12 rows, each with 1–2 thorns); all thorns nondepressible, obliquely oriented to surface of disc, not fitting into slits in integument. Claspers, anterior lobes of pelvic fins, and ventral surfaces of disc and posterior pelvic-fin lobes naked; integument of ventral surface rather delicate.

Skeletal morphology. Neurocranium with nasobasal length 20.7% of distance from snout to posterior margin of cloaca and 80.5% of cranial width. Rostral shaft slender, of moderate length, about 125% of nasobasal length; rostral base 12% of nasobasal length (fig. 4, Table 2); rostral appendices long, flattened anteriorly, subtriangular in cross-section and abutting (rather than fused to) rostral shaft posteriorly; propterygia of pectoral girdle reaching rostral node; nasal capsules very large, ovoid, set at about 26° to transverse axis of neurocranium; foramen for profundus nerve near antero-lateral margin of nasal capsules; preorbital process poorly developed; postorbital process poorly developed and barely distinct from pterotic process; anterior fontanelle very narrow, with acutely rounded apex and bilobed posterior margin, extending to leading edge of nasal capsule; posterior fontanelle indistinct (not visible in radiographs and only detectable after staining and dissection), irregularly notched due to broad margin of acellular perichondrial tissue, fontanelle covered with dense fibrous connective tissue; basal fenestra kidney-shaped; anterior cerebral vein foramen antero-dorsal to optic nerve foramen and above orbito-nasal canal foramina; oculomotor nerve foramen dorsal to optic stalk; jugal arches weak; basal plate and internasal plate relatively narrow, about 28.7% and 12.5% of nasobasal length respectively.

Scapulocoracoid of female moderately short, longer than deep, tapering slightly posteriorly; lateral face expanded slightly between mesocondyle and metacondyle (fig. 5, Table 3); anterior bridge wide, thin, strongly depressed; anterior dorsal fenestra slightly larger than anterior ventral fenestra; scapular process elevated above antero-dorsal margin; anterior corner weakly angular, antero-lateral margin very slightly convex; rear corner not extended distally; mesocondyle slightly depressed; postdorsal fenestra moderately expanded, oval; 3 postventral foramina, central smallest.

Pelvic girdle with short prepelvic processes (fig. 6); iliac processes moderately well developed, strongly recurved; ischiopubic region relatively narrower in males than in females, with straight anterior margin in males and weakly convex margin in females, but with strongly concave posterior margins in both sexes; iliac region with 2–3 obturatorial foramina.

Claspers long, very slender, proximal to and not expanded at origin of glans (fig. 7); without dermal denticles or pseudosiphon; glans weakly depressed, moderately expandable. Inner dorsal lobe with pseudorhipidion extending from level of hypopyle and medial to slit, to about distal quarter of glans; continuing distally almost to glans margin as a fold of integument; lobe with deep cleft lateral to pseudorhipidion; slit proximal to cleft; spur and flag absent. Ventral lobe without shield; pela well developed, extending from level of hypopyle into distal half of glans; projection slightly curved laterally, extending for almost half length of glans from beneath pela to its pointed, naked distal tip near glans margin; spike disc-shaped with sharp, naked lateral and distal margins, ventral to projection, partly covered by sentina but disto-lateral margin visible. Axial cartilage with a slender conical tip; extending well beyond other cartilages (fig. 8). Dorsal marginal cartilage not expanded distally; with a truncate distal border (with the dorsal terminal 2 cartilage) and a long,slender,distomedialextensionformingthepseudorhipidion. Dorsal terminal 1 cartilage relatively narrow and band-like with irregular anterior and posterior margins; located at about midlength of pela and enveloping axial cartilage. Dorsal terminal 2 cartilage rather broad, almost spatulate distally; connected to medial aspect of axial cartilage by well-developed terminal bridge and loosely connected to tip of axial by connective tissue. Ventral marginal cartilage not flared laterally at level of hypopyle; extending almost to distal margin of accessory terminal 2 (as component projection). Ventral terminal cartilage J-shaped; proximo-medial condyle articulating with ventral marginal cartilage, disto-medial extension articulating with tip of axial cartilage; inner limb seated near articulation of accessory terminal 2 and ventral marginal cartilages; acute proximal tip not forming component eperon; disto-lateral margin strongly curved inward and not forming component shield. Accessory terminal 1 cartilage lacking, possibly fused with ventral terminal cartilage to form component projection. Accessory terminal 2 cartilage with large disc-shaped distal extension forming component spike; articulating with postero-medial margin of ventral marginal cartilage.

Colour in preservative. Dorsal surface straw-coloured to pale greyish-yellow, minute melanophores scattered widely over most of surface; ventral surface whitish with translucent skin, palest near margins of disc, minute melanophores lightly scattered over tail. In life, paler, creamish to white above, pinkish over body cavity and head; eyes black; tail brilliant white; skin totally transparent ventrally, viscera distinct.

Size. A small skate attaining at least 448 mm TL and 222 mm disc width; males maturing larger than 360 mm TL.

Distribution. Known from the south-eastern Indian Ocean on the central western sector of the Australian continental slope (between Shark and Nickol Bays, Western Australia), in depths of 590– 760 m. Apparent stenobathic and narrow geographic ranges may not be an artefact; trawl data from depths shallower and deeper, and in areas adjacent the geographic range, included other sympatric rajoid species, but excuded N. hirticauda .

Etymology. A combination of the Latin hirtus (rough or bristly) and cauda (tail) in allusion to the dense coverage of fine denticles on both surfaces of the tail. Known by the vernacular ʻghost skateʼ.

Remarks. Notoraja hirticauda fits the diagnosis of Notoraja as defined by Stehmann (1989) and McEachran and Last (1994), except that the tail is unusually thorny (compared to thorns absent or in a medial row in other Notoraja species), the rostral cartilage (including node) is distinctly longer than the nasobasal length (rather than about equal in length), and the rostral appendices are subtriangular posteriorly and abut the rostral shaft (rather than plate-like and running closely parallel to the shaft). Notoraja hirticauda is further distinguished from its nominal congeners N.laxipella , N.ochroderma , N.subtilispinosa , and N. tobitukai , in proportional measurements, lacking oronasal pits, coloration, and in some skeletal structures. Of these species, Notoraja hirticauda exhibits greatest overall similarity to N. subtilispinosa . It is also superficially similar to N. laxipella but has tail thorns (otherwise absent), a well-developed anterior bridge in the scapulocoracoid (rather than thin or absent), a robust terminal bridge in the clasper (rather than incomplete), and fewer precaudal vertebrae. The relatively long snout of N. hirticauda (preorbital snout length 12.4–13.7%) is more typical of N. laxipella (13.4–14.7% TL) than the other Notoraja species (10.8–12.5% TL). A longer snout is also evident from the prenasal length (10.1–11.0% vs. 8.9–10% TL in these other Notoraja species) and in the shape of the neurocranium (rostral cartilage length 125% in N. hirticauda vs. 88–92% of nasobasal length in N. tobitukai and N. subtilispinosa ). Notoraja ochroderma has a relatively long rostral cartilage (ie. 104% of nasobasal length; McEachran and Last, 1994) but it is still much shorter than that of N. hirticauda . Notoraja ochroderma and N. hirticauda (combined orbit and spiracle lengths 3.5–4.7% TL), and N. hirticauda (4.2–5% TL), have smaller orbits and spiracles than N. tobitukai and N. subtilispinosa (5–5.7% TL).

Members of the genus Notoraja also exhibit significant interspecific variation in the mouth and tail sizes, the pelvic-fin shape, and the gill-slit size and interspacing. Notoraja hirticauda appears to have smaller gill slits (eg. first gill-slit width 0.8–1.2% vs. 1.2–1.5% TL) and narrower intergill distances (eg. width between first gill slits 10.4–11.7% vs. 11.5–13% TL) than N. subtilispinosa . The anterior pelvic-fin lobe varies greatly from slightly shorter in mature males (anterior 93–96% of posterior lobe) to slightly longer than the posterior lobe in most females (typically 104–110%) of N. hirticauda . The anterior lobe is subequal or longer in N. subtilispinosa and N. tobitukai (anterior 100–117% in posterior lobe) and shorter than the posterior lobe in N. ochroderma (anterior 76–90% in posterior lobe). Notoraja hirticauda and N. tobitukai (tail width at pelvic-fin tips 3.2–3.9% TL) have a slightly broader tail than N. subtilispinosa and N. laxipella (width at pelvic-fin tips 2.2–3.1% TL). The four Notoraja species appear to have larger mouths than N. laxipella (5.7–7.2 vs. 4.8–5.5).

The pectoral-fin radial and trunk vertebral counts of N. hirticauda closely resemble those of N. subtilispinosa , N. tobitukai and N. laxipella (ie. 24–27 and 61–67 for vertebral and radial counts respectively). Both counts are higher for N. ochroderma (30–32 and 87–89 for vertebral and radial counts respectively). Similarly, the scapulocoracoid of N. hirticauda is more similar to those of N. subtilispinosa , N. tobitukai and N. laxipella than to that of N. ochroderma which has a relatively more elongate scapulocoracoid with a very large, horizontally expanded post-dorsal fenestra. Notoraja hirticauda has three postventral foramina like female specimens of N. subtilispinosa and N. laxipella examined to date (four in N. tobitukai and five in N. ochroderma ). The pelvic girdle of N. hirticauda most closely resembles that of N. tobitukai . In both species, the anterior contour of the ischiopubic bar is slightly convex and the prepelvic processes are short and rather robust. The prepelvic processes of N. subtilispinosa and N. ochroderma are much more slender and the anterior contour of the ischiopubic bar of the latter is straight ( McEachran and Last, 1994). As discussed above, the neurocranium of N. hirticauda , like N. laxipella , has a relatively long rostral shaft and appendices compared to other species of Notoraja but the presence of jugal arches is shared by N. laxipella and all members of the genus except N. ochroderma .

The fontanelle structure of the neurocranium of N. hirticauda differs from the normal condition found in skates. A posterior fontanelle is well developed in most rajoids. Stehmann (1989) could not detect either anterior or posterior fontanelles in the neurocranium in radiographs of the holotype of N. subtilispinosa , and Ishihara and Stehmann (1990) observed only an anterior fontanelle in radiographs of a second specimen from Indonesia. Similarly, only the anterior fontanelle was detectable in X-rays of the neurocrania of N. hirticauda types, although an ill-defined, posterior aperture overlain with smooth uncalcified cartilage and dense connective tissue was evident from dissection. A similar, poorly-defined posterior fontanelle exits in N. laxipella . In comparison, the posterior fontanelles of other related Australasian skates (ie Notoraja ochroderma , Irolita , Pavoraja and Brochiraja ) are sharply defined in radiographs (Last and McEachran, unpubl.).

The rostral appendices are considered to be important evolutionary characteristics (McEachran, 1984: McEachran and Miyake, 1990). Three Notoraja species ( N. tobitukai , N. subtilispinosa and N. ochroderma ) are considered to possess plate-like rostral appendices ( Stehmann, 1989; McEachran and Last, 1994). These structures are thickened, almost triangular in cross-section distally in N. hirticauda , and more closely resemble the subconical appendices found in N. laxipella and Brochiraja . Further inspection of the neurocranium of N. laxipella revealed a relatively thinner, rostral cartilage separated slightly from its appendices (rather than continuously abutting them as in N. hirticauda ).

The external form of the clasper of N. hirticauda is consistent with the general type found in Brochiraja and Notoraja , except for N. ochroderma , which has an eperon and a shield formed by the sharp proximal margin of the ventral terminal cartilage ( McEachran and Last, 1994). The dorsal terminal 1 cartilage, small in N. hirticauda , is absent in N. ochroderma and sometimes absent in N. tobitukai . McEachran and Last (1994) suggested that the “rhipidion” of Notoraja , Pavoraja and Irolita is structurally different and probably not homologous with the rhipidion of Ishiyama (1958, 1967), Stehmann (1970) and Hulley (1972), that occurs in the majority of skate taxa in Group II ( McEachran and Miyake, 1990). Ishiyama (1958, 1967) applied the terms pent and pela to this structure but since pent has been proposed for a separate component, the “rhipidion” of Group I should be called the pela to avoid further confusion.

Within Notoraja , only N. ochroderma and N. hirticauda are whitish on both dorsal and ventral surfaces. N. ochroderma possesses oronasal pits which are lacking in all other Notoraja species. The dorsal squamation of N. hirticauda , consisting of fine, erect but slightly recurved denticles, is similar to N. subtilispinosa , N. ochroderma and N. laxipella . Also, the tail of N. hirticauda and N. ochroderma , unlike the other two species, has irregular rows of small thorns. However, unlike N. ochroderma , the ventral surface of the tails of N. hirticauda and the other Notoraja species are covered in denticles.

Much of the pavorajine skate fauna of the Indo-Pacific remains undescribed. Within the known fauna, N. hirticauda appears to be much more similar to N. subtilispinosa and N. laxipella than either N. ochroderma or N. tobitukai , and the supraspecific structure of the Notoraja group needs further investigation. McEachran and Last (1994) noted that N. ochroderma did not fit the synapomorphy scheme of either Notoraja or Pavoraja but tentatively placed it in Notoraja as a conservative measure. Yearsley and Last (1992), who demonstrated similarities between the subgenus Insentiraja and Notoraja , temporarily placed the former in Pavoraja based on McEachranʼs earliest synapomorphy scheme (1984) and stressed the need for a review of Indo-Pacific pavorajines. A study of the relationships of Australian and New Zealand skates is now in progress by McEachran and Last (unpubl.).

Figures

Figure 1. Notoraja hirticauda sp. nov. Holotype (CSIRO H1816–02, 446 mm TL, male). a. Dorsal view; b. Ventral view.

Figure 2. Notoraja hirticauda sp. nov. Paratype (CSIRO CA2824, 361 mm TL, female). Dorsal view.

Figure 3. Squamation on the mid-tail of Notoraja hirticauda sp. nov. Holotype (CSIRO H1816–02, 446 mm TL, male). a. Dorsal view; b. Lateral view.

Figure 4. Neurocranium of Notoraja hirticauda sp. nov. Paratype (CSIRO H1822–01, mature female, 372 mm TL: a. dorsal view; b. lateral view; c. posterior view). fig. abbreviations: ac–anterior cerebral vein foramen, af–anterior fontanelle, antc–antorbital condyle, bf–basal fenestra, end– endolymphatic foramen, es–efferent spiracular artery foramen, hf–hyomandibular facet, into–intercerebral vein foramen, ja–jugal arch, lbX– lateralis branch of vagus nerve foramen, obf–otic branch of facial nerve foramen, oc–occipital condyle, of–orbital fissure, onc–orbitonasal canal foramen, os–optic stalk, peri–perilymphatic nerve foramen, pf–posterior fontanelle, poc–preorbital canal, postp–postorbital process, prep– preorbital process, prof–profundus nerve foramen, pterp–pterotic process, ra–rostral appendix, rb–rostral base, rn–rostral node, rs–rostral shaft, II–optic nerve foramen, III–oculomotor nerve foramen, VII–hyomandibular branch of facial nerve foramen, IX–glossopharyngeal nerve foramen, X–vagus nerve foramen.

Figure 5. Lateral view of left scapulocoracoid of Notoraja hirticauda sp. nov. Paratype (CSIRO H2574–06, mature female, 428 mm TL). fig. abbreviations:ab–anterior bridge,ac–anteriorcorner,adf–anterodorsalfenestra,avf–anteroventralfenestra,msc–mesocondyle,mtc–metacondyle, pdf–postdorsal fenestra, prc–procondyle, pvf–postventral foramina, rc–rear corner, scp–scapular process.

Figure 6. Ventral view of pelvic girdle of Notoraja hirticauda sp. nov. a. Holotype, (CSIRO H1816–02, male, 446 mm TL); b. Paratype (CSIRO H2574–06, female, 428 mm TL). fig. abbreviations: ilp–iliac process, obf–obturator foramina, prep–prepelvic process.

Figure 7. Lateral view, partially expanded, of right clasper of Notoraja hirticauda sp. nov. Holotype (CSIRO H1816–02, 446 mm TL, male). fig. abbreviations: cf–cleft, hy–hypopyle, pj–projection, pr– pseudorhipidion, rh–rhipidion, sl–slit, sp–spike.

Figure 8. Right clasper cartilages of Notoraja hirticauda sp. nov. Holotype (CSIRO H1816–02, 446 mm TL, male): a) lateral view; b) dorsal view; c) ventral view. fig. abbreviations: atr2–accessory terminal 2 cartilage, ax–axial cartilage, dmg–dorsal marginal cartilage, dtr1–dorsal terminal 1 cartilage, dtr2–dorsal terminal 2 cartilage, tb–terminal bridge, vmg–ventral marginal cartilage, vtr–ventral terminal cartilage.