Bathyraja (Arctoraja) sexoculata Misawa, Orlov, Orlova, Gordeev & Ishihara, 2020
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publication ID |
https://doi.org/ 10.11646/zootaxa.4861.4.3 |
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publication LSID |
lsid:zoobank.org:pub:18AE5F50-D213-496C-90D0-9E625C1A15B2 |
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DOI |
https://doi.org/10.5281/zenodo.4416841 |
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persistent identifier |
https://treatment.plazi.org/id/4D7B4A72-2F76-4A17-8E06-E70284654A09 |
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taxon LSID |
lsid:zoobank.org:act:4D7B4A72-2F76-4A17-8E06-E70284654A09 |
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treatment provided by |
Plazi |
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scientific name |
Bathyraja (Arctoraja) sexoculata Misawa, Orlov, Orlova, Gordeev & Ishihara |
| status |
sp. nov. |
Bathyraja (Arctoraja) sexoculata Misawa, Orlov, Orlova, Gordeev & Ishihara sp. nov.
urn:lsid:zoobank.org:act:4D7B4A72-2F76-4A17-8E06-E70284654A09
( Figs. 2–7 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 ; Table 2 View TABLE 2 )
New English name: Simushir skate; new Russian name: CимУШирский скат
Holotype. ZMMU-P 24098, 346 mm TL, immature male, off the Pacific coast of Simushir Island, Kuril Islands, Russia, 46º44.8′N, 151º52.5′E, 150 m depth, 24 March 2017, INSDC LC 426928 View Materials . GoogleMaps
Paratypes. Four specimens (three males and one female). All paratypes collected with holotype. ZMMU-P GoogleMaps 24095, 346 mm TL, immature male, LC 426926 View Materials , ZMMU-P 24096 , 326 mm TL, immature male, LC 426927 View Materials , ZMMU- P 24097, 352 mm TL, immature male, LC 426924 View Materials , ZMMU-P 24099 , 286 mm TL, immature female, LC 426925 View Materials .
Diagnosis. A medium-sized species (approximate maximum size 800 mm TL, 550 mm DW) of Bathyraja (Arctoraja) with the following combination of characters: dorsal ground color reddish-brown or greenish-brown, with three pairs of white blotches on disc located beside eyes, and on shoulders and posterior half of disc; lateral margin of tail with four or five pairs of white blotches located at tail origin, midpoint, D1 origin, and on inter-dorsal space; ventral surface almost entirely white; dark blotch around cloaca, dark bands along mid ventral line of tail; dorsal surface of disc with a single scapular thorn, 3–4 nuchal thorns; tail with 20–24 regularly arranged thorns; median row of thorns discontinuous, viz., mid-dorsal thorns absent; orbital thornlets present along medial rim of orbit; fine prickles on dorsal surface of disc and tail; prickle band on mid-disc extending along sides of tail; prickles on pectoral fin base relatively sparse; ventral surface uniformly smooth; disc width 63.1–65.6% TL, length 50.6–53.5% TL; anterior projection (snout to maximum width) 29.7–32.2% TL; head length (dorsal aspect) 18.9–20.6% TL; snout broad, moderately short, preoral length 11.1–14.1% TL, supported by slender, flexible unsegmented cartilage; snout angle 103–119º; eyes rather large, eye diameter 0.22–0.24 times head length, 1.00–1.11 times between orbits; tail relatively long (but shorter than disc width), length 51.5–54.1% TL and 0.79–0.86 times DW, width at first dorsalfin origin 3.8–4.2% tail length; 86–93 predorsal caudal vertebrae.
Description. Proportional morphometrics and meristics of type specimens given in Table 2 View TABLE 2 .
External features: Body size moderately large, young male holotype about 350 mm TL ( Fig. 2 View FIGURE 2 ), mature males reach at least 800 mm TL ( Fig. 6A, B View FIGURE 6 ). Disc rhombic, moderately broad, width 1.25 (range: 1.23–1.28) times length; anterior margin almost straight or weakly rounded, clearly convex in adult males; posterior margin moderately rounded; free rear tip broadly rounded; maximum angle in front of spiracles 112º (103–119º); widest point much closer to tail than to snout. Head moderately small, ventral head length 25.6% (25.8–28.7%) TL; snout moderately short, broad and blunt, preorbital length 2.90 (2.69–3.11) times eye diameter, 3.22 (2.68–3.30) times interorbital width. Rostral lobe short, slightly produced, without fleshy process at apex. Eyes rather large, diameter 1.11 (1.00– 1.06) times interorbital width; interorbital space width moderate, slightly concave. Spiracle opening oval, relatively small, length 0.66 (0.59–0.79) times eye diameter, extending slightly forward of posterior margin of eye; between spiracle width 0.38 (0.36–0.44) times dorsal head length.
Nostril openings small, well separated from each other, internarial distance 0.73 (0.70–0.91) times prenarial length; lateral nasal flap moderately developed. Nasal curtain well developed, length 0.60 (0.48–0.54) times internarial distance; lateral margin expanded and notched beside lateral nasal flap. Upper and lower jaws slightly arched; anterior teeth rows on both jaws slightly exposed, lateral teeth barely concealed by nasal curtain. Teeth unicuspid, with slightly elevated subcircular bases; arranged regularly in parallel longitudinal rows; cusps weakly pointed, conical, directed obliquely posteriorly in upper jaw; cusps more flattened in lower jaw. Gill slit openings small, well separated from each other, between first gill slits 0.74 (0.72–0.82) times ventral head length.
Tail slightly depressed, moderately broad, tapering weakly, and gradually intermediary; width at pelvic-fin posterior margin 1.75 (1.80–2.21) times width at first dorsal-fin origin; depth at pelvic-fin posterior margin 2.87 (2.06–2.68) times depth at first dorsal-fin origin; length from posterior margin of cloaca 1.18 (1.06–1.15) times distance from margin to snout tip; anterior cross-section equally convex dorsally and ventrally, more strongly convex posteriorly on dorsal surface than ventral surface, almost flat ventrally near tail apex; width 1.43 (1.32–1.49) times depth at pelvic-fin end, 2.34 (1.61–1.86) times depth at first dorsal-fin. First and second dorsal fins moderate, similar shape and size; first dorsal-fin vertical height 0.60 (0.47–0.70) times its basal length; second dorsal-fin vertical height 0.60 (0.55–0.79) times its basal length; basal length of first dorsal-fin 1.28 (0.92–1.21) times that of second dorsal-fin, vertical height of first dorsal-fin 1.27 (1.00–1.07) times that of second dorsal-fin; anterior margins and apices rounded, posterior margins almost straight; distance between dorsal fin bases 0.21 (0.26–0.52) times first dorsal-fin base length; distance from first dorsal-fin to tail tip 2.83 (3.16–3.75) times first dorsal-fin base length, 0.22 (0.23–0.27) times tail length. Caudal fin relatively small, caudal-fin length 0.60 (0.66–1.08) times first dorsalfin base length, vertical height 0.20 (0.15–0.37) times first dorsal-fin height; hypochordal caudal-fin lobe poorly developed. Lateral tail folds poorly developed, more apparent behind mid-tail, terminating near tail tip, broadest beneath first dorsal-fin; width 1.28 (0.89–1.66) times caudal fin vertical height.
Pelvic fins moderately sized, clearly notched forming two lobes (anterior and posterior lobes); anterior lobe relatively short, narrowly rounded distally, lateral margin entire, inner margin incised, and tip weakly pointed; posterior lobe moderately elongate, lateral margin rounded, inner margin almost straight, free rear tip pointed; anterior lobe length 0.61 (0.56–0.64) times that of posterior lobe; pelvic base width 15.0% (14.9–17.7%) TL. Clasper moderately depressed, slender, slightly elongated (not calcified in immature specimens) ( Fig. 4B View FIGURE 4 ); length 8.3% (8.5–10.1 %) TL.
Internal features: Rostral shaft (rostral cartilage) slender, flexible, slightly undulating, base unsegmented. Anteriormost portion of pectoral-fin radials and propterygium extending almost to snout tip ( Fig. 7A View FIGURE 7 ). Pelvic girdle somewhat broad and weakly arched, with 1? –2? obturator foramen on each side (not clearly visible on radiograph), iliac processes rather short and curving inwards, prepelvic processes well developed ( Fig. 7B View FIGURE 7 ).
Merisitics: Predorsal tail thorns 23 (19–22), inter-dorsal space with single thorn, total tail thorns (including inter-dorsal thorn) 24 (20–24); nuchal thorns 3 (3 or 4); mid-dorsal thorns absent; scapular thorn 1 (0 or 1). Tooth rows 27 (25–27) in upper jaw, 25 (24 or 25) in lower jaw. Precaudal vertebrae 35 (37–39), predorsal caudal vertebrae 93 (86–91), total vertebrae 128 (123–130). Pectoral-fin propterygial radials 35 (34–36), mesopterygial radials 17 (15), metapterygial radials 30 (29–32), total pectoral-fin radials 82 (79–82). Anterior pelvic-lobe radials 4 (4 or 5), posterior pelvic-lobe radials 18 (16–19), total pelvic-fin radials 22 (21–23).
Squamation ( Figs. 2–4 View FIGURE 2 View FIGURE 3 View FIGURE 4 ): Dorsal surface with denticles (including both thornlets and prickles) distributed along pectoral-fin margins, snout, interorbital space, along mid-disc to lateral margins of tail, posterior pelvic lobe, dorsal and caudal fins ( Fig. 2A View FIGURE 2 ); thornlets (each with large stellate base and strongly pointed cusp) along orbital rims and anterior pectoral-fin margins ( Fig. 3A View FIGURE 3 ); prickles (each with small oval base and weakly pointed cusp) concentrated from mid-disc to lateral margins of tail, less dense on snout and posterior pectoral-fin margins, and sparse on pectoral-fin base, posterior pelvic lobe, dorsal and caudal fins ( Fig. 3 View FIGURE 3 ); denticle band obvious from mid-disc to lateral margins of tail ( Fig. 3A, B View FIGURE 3 ); midline of tail at base of thorns smooth ( Fig. 3C View FIGURE 3 ). Ventral surface entirely smooth ( Figs. 2B View FIGURE 2 , 4 View FIGURE 4 ).
Coloration ( Figs. 2–6 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 ). Dorsal ground color reddish or greenish-brown, with three pairs of regularly arranged white blotches on disc, located beside eyes (medium-sized, oval), and on shoulders (small, round) and posterior half of disc region (large, oval) ( Figs. 2A View FIGURE 2 , 5 View FIGURE 5 , 6 View FIGURE 6 ); tail with four or five pairs of white blotches, at origin, mid-point, in front of dorsal-fin origin, and on inter-dorsal space ( Fig. 5A View FIGURE 5 ); some large specimens covered with numerous dark specks ( Fig. 6A, C View FIGURE 6 ). Ventral ground color broadly white; around cloaca with dark greyish blotch, margins of disc and pelvic fins, and tail with dark greyish bands ( Fig. 4 View FIGURE 4 ); irregular dark pigment scattered on central disc and on pelvic fin region in young specimens; dark blotch, bands, and pigment less distinct in large specimens ( Fig. 6B, D View FIGURE 6 ).
Following formalin fixation and storage in 70% ethanol: dorsal ground color greyish-brown, white blotches relatively indistinct ( Figs. 2A View FIGURE 2 , 5A View FIGURE 5 ); ventral ground color dull whitish, margins of disc and pelvic fins, and tail greyish-brown ( Figs. 2B View FIGURE 2 , 4 View FIGURE 4 , 5B View FIGURE 5 ).
Size. The type material comprised young individuals 286–352 mm TL, 187–226 mm DW ( Table 2 View TABLE 2 ). The holotype and male paratypes all lacked malar thorns and elongation of the claspers. Uncatalogued specimens (not kept after collection) identified as Bathyraja sexoculata by having three pairs of white blotches on disc included one adult male (ca. 810 mm TL, ca. 550 mm DW), two immature males (claspers not calcified, but with malar thorns) (ca. 560 mm TL, ca. 370 mm DW and ca. 850 mm TL, ca. 570 mm DW, respectively), and an immature female (ca. 630 mm TL, ca. 450 mm DW) (see Fig. 6 View FIGURE 6 ). The smallest male with malar thorns was ca. 560 mm TL. It appeared that males of this species mature at about 800 mm TL (at least), but that size at initial maturity was variable.
Distribution. All type specimens were collected from the east coast of Simushir Island, Kuril Islands, North Western Pacific, depth at 150 m ( Fig. 1 View FIGURE 1 ). Similarly, uncatalogued specimens ( Fig. 6 View FIGURE 6 ) were also collected from around Simushir Island. At present, only B. sexoculata is recognized from this region.
Etymology. The scientific name sexoculata refers to the color pattern of the species, i.e., six white blotches (ocelli) on the dorsal disc: sex (Latin) = six; oculus (L.) = eye. The new Russian and English names are derived from the type locality.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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