Notoraja inusitata, Séret & Last, 2012

Séret, Bernard & Last, Peter R., 2012, New deep water skates of the genus Notoraja Ishiyama, 1958 (Rajoidei, Arhynchobatidae) from the southwest Pacific, Zoosystema 34 (2), pp. 319-341 : 328-332

Notoraja inusitata n. sp.

( Figs 9-12 ; Tables 2, 3)

Notoraja sp. 2 – Séret in Fricke et al. (2011): listed p. 5.

HOLOTYPE. — MNHN 2008-1638 (field number DHS 733, tissue sample ICTI-001845), male juvenile 444 mm TL, SANTO expedition, R / V Alis , Vanuatu, Espiritu

Santo Island, Big Bay, stn 107, 14°58.6’S, 166°52.5’E, 807/ 844 m depth, beam trawl, 16.X.2006.

DISTRIBUTION. — Known only from Big Bay, Espiritu Santo ( Vanuatu), from 807 to 844 m depth ( Fig. 18 ).

ETYMOLOGY. — In the absence of an adult male, the generic placement of this ray initially proved to be problematic; its head and disc morphology resemble some species of Sinobatis Hulley, 1973 , Bathyraja Ishiyama, 1958 and Insentiraja. Hence, we have used the Latin “inusitatus” (unusual, strange) to allude to the strange appearance of this ray.

DIAGNOSIS. — A species of Notoraja (probably of medium size as male 440 mm TL is juvenile) with the following combination of characters: disc broadly heart-shaped, snout tip projecting as a short blunted triangle, single preorbital thorn; dorsal surface of disc entirely velvety, covered with very fine denticles; ventral surface of disc naked; tail long and tapering from base to first dorsal fin, slightly expanded at level of dorsal fins; tail entirely pricked except for the ventral base, an irregular mediodorsal row of small denticles on tail; lateral tail folds expanded at level of dorsal and caudal fins, but width less than tail width; low epichordal caudal-fin lobe; nasal lobes not greatly expanded, width of nasal curtain 7.7% TL; mouth relatively narrow, its width less than 66% of maximum width of nasal curtain and 5.1% TL; anterior and posterior pelvic-fin lobes subequal in length; dorsal surface pale greyish brown, ventral surface whitish. Total pectoral-fin radials 74, monospondylous centra 27, total diplospondylous centra 116, total centra 143.

DESCRIPTION

Disc broadly heart-shaped, 1.10 times as broad as long; maximum angle in front of spiracles 93°; snout tip projecting as a short blunt triangle, rostral cartilage clearly visible dorsally and ventrally, not concealed by thick skin; anterior margin of disc very weakly undulated, slightly and regularly convex from base of snout tip to level of spiracles; outer corner and posterior margins broadly rounded. Axis of greatest width 57% of disc length. Preorbital snout length 3.72 times orbit length, 3.73 times interorbital width; preoral snout length 2.14 times internarial distance. Orbit diameter subequal to interorbital distance, and 1.76 times length of spiracles. Nasal lobes not greatly expanded and rounded, posterior margin weakly and coarsely fringed.Mouth relatively small, its width only about 66% of maximal width of nasal curtain. Upper and lower jaws weakly arched on either side of symphysis. Teeth plate-like, with short cusps and arranged in quincunx. Distance between first gill slits 1.57 times larger than between nostrils; distance between fifth gill slits subequal to internarial distance.

Pelvic fins deeply incised with lobes connected by radials and membranes, anterior lobe long, subequal in length to posterior lobe; posterior lobe with convex lateral margins, posterior margin crenate due to extension of posterior radials. Tail long and tapering from base to first dorsal fin, slightly expanded at level of dorsal fins, then tapering to tail tip; tail only weakly depressed at its base, almost oval in cross-section; more depressed from midlength, only weakly convex ventrally; width at axils of pelvic fins 1.83 times width at midlength of tail, and 2.74 times width at dorsal-fin origin respectively; length from rear of cloaca 1.37 times distance from tip of snout to rear of cloaca; lateral skin folds originating anteriorly to tips of posterior pelvic-fin lobes, extending to distal half to distal fourth of epichordal caudal-fin lobe and broadening distally from about level of first dorsal fin to epichordal lobe of caudal fin; however, fold width less than tail width. Dorsal fins of similar shape and size; rather short and moderately tall with evenly convex anterior margin, straight or slightly convex posterior margin and a pointed tip; separated by an interspace, 52% length of first dorsal-fin base. Epichordal caudal-fin lobe low, separated by short interspace from and distinctly longer than second dorsal-fin base; hypochordal caudal lobe very small, low, originating near end of lateral fold, confluent with epichordal lobe.

Dorsal surface of disc densely and finely prickled, denticles bristle-like; denticles erect with very slightly curved crowns, on radiate base embedded in skin. A single small, but conspicuous preorbital thorn. Tail prickled dorsally; an irregular mediodorsal row of about 45 small thorns extending from level of pelvic axil to first dorsal-fin origin; thorns with oval, radiate root and a compressed, hooked crown.Ventral surface of disc and pelvic fins totally naked. Ventral surface of tail fined prickled, its base naked. No malar or alar thorns in this juvenile male holotype.

Tooth rows in upper jaw 41; lower jaw 38. Pectoral propterygial radials 32; mesopterygial radials 16; metapterygial radials 26; total radials 74. Monospondylous centra 27; diplospondylous predorsal centra 81; predorsal centra 108; caudal centra 35; total diplospondylous centra 116; total centra 143. Colour (in preservative)

Dorsal surface pale greyish brown; eyes, dorsal-fin and caudal-fin margins, and lateral tail folds darker. Ventral surface whitish, with small pale brownish blotches scattered mainly on outer disc margins and on anterior pelvic lobes; cloaca whitish surrounded by faded brownish markings.

Size

Known only from the juvenile male holotype of 440 mm TL.

REMARKS

Although described from a single juvenile male, this species has distinctive morphological and meristic features that set it clearly apart from its congeners and all other skates of the region. Its general appearance resembles some species of Bathyraja and Indo-Australian legskates (family Anacanthobatidae von Bonde & Swart, 1924 ) in having a thin, flabby disc, and long, projecting snout with a narrow, twisted rostral cartilage that is visible both dorsally and ventrally. However, its tail shape is more typical of skates than legskates (thicker, with well-developed dorsal fins, lateral tail folds and denticles). Like other species of Notoraja , it has a rostral cartilage continuous with chondrocranium, stout proximally but very slender and uncalcified distally ( Fig. 12 ), broadly oval nasal capsules with basal fenestrae (vs narrow capsules without basal fenestrae in Bathyraja ) and a narrow internasal plate in the chondrocranium (broad in Bathyraja , see McEachran & Miyake 1990), the precerebral fontanelle is narrow and extends anterior to leading edge of the nasal capsules (vs broad precerebral fontanelle not extending anterior to nasal capsules in Bathyraja , see McEachan & Dunn 1998), and lower abdominal vertebral counts (27 vs 28-48, rarely fewer than 30 in Bathyraja ; Stehmann 2005). Based on meristic data for 21 species of Bathyraja ( Stehmann, 2005) , only B. richardsoni (Garrick, 1961) has an equally high tooth row count in the upper jaw (41 in N. inusitata n. sp. and 44 in B. richardsoni vs 18-36 in the other 20 species). Notoraja inusitata n. sp. can be distinguished from other Notoraja species of the region by the features discussed above, its small but distinctly triangular snout tip, naked ventral disc, configuration of the medio-dorsal thorns on the tail, broader lateral tail folds originating at the level of the posterior lobe of the pelvic fin, and more pectoral-fin radials (74 vs 62-66) than its congeners.

The genus Insentiraja was initially defined as a subgenus of Pavoraja Whitley, 1939 by Yearsley & Last (1992) for their new species P.laxipella . It is defined by the absence of thorns on tail and mid-dorsal region of trunk, and presently includes I. laxipella and I. subtilispinosa ( Stehmann, 1989) . Our new species bears some resemblance to Insentiraja skates (e.g., soft body with loose skin, ventral skin almost transparent) but differs in having a distinct mid-dorsal row of thorns on its tail. Our specimen is a juvenile male and this row might atrophy with growth, but other characters distinguish it from Insentiraja skates: e.g., less dense covering of dermal denticles on the dorsal surface of the disc and ventral surface of the tail, greater numbers of precaudal vertebrae (116 vs 95-95) and pectoral radials (74 vs 64-66); see Yearsley & Last 1992 and Ishihara & Stehmann 1990.

Figures

FIG. 9. — Notoraja inusitata n. sp., holotype (MNHN 2008-1638, male juvenile 444 mm TL):A, dorsal surface;B, ventral surface. Scale bar: 10 cm.

FIG. 10.— Dorsal head of Notoraja inusitata n.sp.,holotype (MNHN 2008-1638, male juvenile 444 mm TL). Scale bar: 1 cm.

FIG. 18.— Oronasal region of Notoraja longiventralis n.sp., holotype (MNHN 1999-0449, male juvenile 434 mm TL). Scale bar: 1 cm.

FIG. 12.— Radiograph of the head of Notoraja inusitata n. sp.,holotype (MNHN 2008-1638, male juvenile 444 mm TL).Scale bar:1 cm.