Rhinobatos sainsburyi, Last, 2004

Last, Peter R., 2004, Rhinobatos sainsburyi n. sp. and Aptychotrema timorensis n. sp. - Two New Shovelnose Rays (Batoidea: Rhinobatidae) from the Eastern Indian Ocean, Records of the Australian Museum 56 (2), pp. 201-208 : 205-208

Rhinobatos sainsburyi n.sp.

Figs. 3 , 4 , Plate 1 b, Table 1

Rhinobatos sp. 1 .—Gloerfelt-Tarp & Kailola, 1984: 29, fig.

(CSIRO CA2863, NW of Port Hedland, Western Australia). Rhinobatos sp. 4 .—Gloerfelt-Tarp & Kailola, 1984: 30, fig.

(CSIRO CA1257, NE of Monte Bello Is, Western Australia). Rhinobatos sp. 1 .— Sainsbury et al., 1985: 44, pl. (CSIRO

CA2863, NW of Port Hedland, Western Australia). Rhinobatos sp. 2 .— Sainsbury et al., 1985: 44, pl. (CSIRO

CA1257, NE of Monte Bello Is, Western Australia). Rhinobatos sp. A .—Last & Stevens, 1994: 284, 289, pl. 39, figs.

Type material. HOLOTYPE: CSIRO H.4041-04, mature male, 506 mm TL, 19°29'S 117°35'E, NE of Cape Lambert , Western Australia, 70 m, 1 Sep. 1995 . PARATYPES: CSIRO CA1129 , ♀, 490 mm TL, 18°38'S 119°19'E, NE of Bedout Island , Western Australia, 125 m, 6 Jun. 1980 ; CSIRO CA3901 , mature Ƌ, 489 mm TL, 18°54'S 117°44'E, NW of Port Hedland , Western Australia, 148 m, 30 Jan. 1983 ; CSIRO H.743-01, ♀, 595 mm TL, 20°19'S 115°03'E, west of Monte Bello Islands , Western Australia, 92 m, 12 Oct. 1986 ; CSIRO H.757-01, immature Ƌ, 376 mm TL, 19°00'S 118°03'E, NW of Port Hedland , Western Australia, 116 m, 22 Oct. 1986 ; CSIRO H.1048-01, mature Ƌ, c. 460 mm TL, 18°37'S 118°20'E, south of Rowley Shoals , Western Australia, 137 m, 25 Sep. 1987 ; CSIRO H.1050-03, ♀, 542 mm TL, 18°52'S 118°38'E, north of Port Hedland , Western Australia, 100 m, 26 Sep. 1987 ; CSIRO H.1058-02, ♀, 434 mm TL, 19°04'S 118°11'E, NW of Port Hedland , Western Australia, 86 m, 26 Sep. 1987 ; CSIRO H.1090-01, ♀, 532 mm TL, 19°38'S 117°06'E, north of Nickol Bay , Western Australia, 70 m, 3 Oct. 1987 ; CSIRO H.1091-01, ♀, 530 mm TL, 19°53'S 116°06'E, NW of Dampier Archipelago , Western Australia, 66 m, 4 Oct. 1987 ; CSIRO H.1091-03, ♀, 503 mm TL, 19°53'S 116°06'E, NW of Dampier Archipelago , Western Australia, 66 m, 4 Oct. 1987 ; CSIRO H.1091-04, ♀, 557 mm TL, 19°53'S 116°06'E, NW of Dampier Archipelago, WesternAustralia , 66 m, 4 Oct. 1987 ; CSIRO CA1253 , mature Ƌ, 531 mm TL, 9°52'S 129°14'E, north of Joseph Bonaparte Gulf , Northern Territory, 158 m, 9 Jul. 1980 .

Diagnosis. A Rhinobatos distinguished by the following combination of characters: disc wedge-shaped, its dorsal surface scaled but without thorns; snout short, snout length

2.5–2.6 times interspiracular distance; orbit moderately large, diameter 1.6–1.9 times spiracle length; nostrils oblique, length 1.4–1.6 times internarial distance; anterior nasal-flaps inserted well into internarial space, but never almost united near ventral midline; posterior nasal flaps broad; ridges of rostral cartilage well-separated dorsally and almost parallel; prebranchial sensory-pore patch narrow, extending to first gill slit; distance between first gill slits 1.3–1.4 times distance between fifth gill slits; distance between fifth gill slits 2.5–2.9 times in ventral head length; postscapular sensory canal long, not grooved, extending more than three-quarters distance to pectoral-fin insertions; moderately tall dorsal-fins; pelvic-fin inner margin distinctly longer than its base in mature males but shorter than base in females; interdorsal distance more than 2.5 times first dorsal-fin base; outer spiracular fold distinctly larger than inner fold; dorsal margin of caudal fin about 2.0–2.2 times preventral margin; 162–171 post-synarcual vertebral centra; about 50 nasal lamellae; and dorsal disc plain brownish or with faint dusky blotches or fine dark spots.

Description. Disc wedge shaped, angular anteriorly, angle anterior to eyes about 66°; outer margins broadly rounded, narrowly rounded distally, length 1.29 in mature Ƌ holotype (1.24–1.29 in 5 paratypes) times width ( Table 1). Pelvic fins relatively short, relatively short-based in mature Ƌ, base length about 0.82 of inner margin (much longer in paratypes, 1.07 times in young Ƌ paratype, 1.22–1.60 times in 4 ♀ paratypes); total length 1.98 (1.92 and 1.60–1.81) times their base length, 2.42 (2.64–2.85) times width; anterior margin weakly double concave, apex broadly rounded, posterior margin convex. Tail slender; in cross-section nearly flat ventrally, rounded dorsally; tail length from anterior cloaca 1.67 (1.47–1.57) times precloacal length, 1.64 (1.47–1.55) times disc length, 5.83 (5.43–6.02) times body width at pelvic-fin insertions; tail width 2.23 (2.16–2.28) times depth at pelvic-fin insertions, 2.53 (2.40–2.73) at first dorsal-fin origin, 2.02 (2.04–2.32) at second dorsal-fin origin. Dermal fold ventrolateral on tail, originating slightly anterior to free rear tip of pelvic fin, reaching just behind ventral caudalfin origin; fold well developed, maximum width in interdorsal space about a half width of posterior nasal flap.

Head rather short, ventral length 24.7% (23.3–26.7%) TL; snout short and narrowly rounded; preoral snout length 2.95 (2.98–3.29) times mouth width, 6.59 (5.98–7.25) times internarial distance, 1.16 (1.09–1.23) times dorsal caudalfin margin, 5.78 (4.80–5.76) times distance from nostril to margin of disc; snout length (direct) 2.60 (2.46–2.59) times interspiracular length, 3.31 (3.30–3.58) times orbit diameter, 4.61 (3.74–4.06) times interorbital width; interorbital space almost flat, rather narrow; eyes moderately small, not elevated or protruding, relatively larger in mature Ƌ, orbit diameter 1.90 (1.59–1.77) times spiracle length, 1.39 (1.06– 1.15) times interorbital width. Spiracle lunate, moderately large; two weakly compressed spiracular folds on posterior margin, innermost fold half or less length of outer fold; distance between bases of folds subequal to length of inner fold. Nostril moderately large, oblique, nasal flaps well developed; anterior aperture subrectangular to ovoid, width well exceeding length; nostril length 3.47 (3.01–3.54) times anterior aperture width, 1.56 (1.37–1.56) times anterior nasal-flap base length, 1.44 (1.04–1.27) times distance from nostril to edge of disc, 1.64 (1.37–1.63) times internarial width. Anterior nasal flap broad with long, bluntly pointed process anteriorly; flap base 1.56 (1.67–1.94) times its width at process, 2.22 (2.02–2.45) times anterior aperture width; inserted well into internarial space, not at nostril margin, distance between their insertions 3.75 (3.73–4.51) in distance between lateral margins of anterior apertures, 1.09 (1.07–1.24) in internarial width; process of flap about twice as long as wide at its base, overlapping posteromesial edge of posterolateral nasal flap and determining inner margin of anterior aperture. Posterolateral nasal flap lobe-like, width uniform along most of hind margin of anterior aperture, length 4.78 (4.38–5.68) times width; originating at lateral extremity of anterior nasal aperture, extending posteriorly as free fold (below anterior fold and above posterior fold along lateral margin of nostril) to about level of insertion of anterior nasal flap. Posterior nasal flap strongly lobate, base length 2.57 (2.72–3.18) times its width, not reaching end of nostril, inserted well forward of posterior tip; width subequal to anterior aperture width, 1.74 (1.22–1.65) times posterolateral nasal-flap width. Nasal lamellae 51. Mouth moderately wide, width 1.36 (1.37–1.46) times nostril length, 6.73 (7.33–7.78) in precloacal length; positioned just in advance of hind margin of orbit; jaws not greatly thickened. Upper jaw weakly double concave, upper lip arched slightly, no preoral groove; lower lip pronounced,

not separated from post-oral groove by ridges of strongly corrugated skin; weak lateral grooves around corners of mouth. Teeth small, blunt, crowns rhomboidal with weak, pointed posterior cusps; teeth quincuncial, about 80 rows in upper jaw; upper and lower jaw teeth similar in shape and size. Gill openings weakly s-shaped (apart from fifth); length of third gill slit 3.18 (2.68–2.96) in nostril length, 6.63 (6.72–7.10) in distance between fifth gill slits; distance between first gill slits 1.35 (1.26–1.41) times distance between fifth gill slits; distance between fifth gill slits 3.42 (3.47–4.09) times internarial distance, 1.53 (1.67–1.82) times mouth width, 2.51–2.94 times in ventral head length.

Dorsal-fins of moderate size, relatively upright; semifalcate, apices narrowly rounded rather than angular; anterior margins convex distally, posterior margins concave; free rear tips forming right angle; first dorsal-fin marginally taller than second, length of first 0.95 (0.92–1.00) times its height, base length 1.79 (1.72–1.88) times inner margin length; second dorsal-fin length 1.02 (1.02–1.11) times its height, base length 2.12 (2.04–2.58) times inner margin length. First dorsal-fin relatively close to pelvic-fin insertion, interspace 0.74 (0.75–0.83) times interdorsal distance; interdorsal space relatively short, 2.00 (1.86–2.01) times second dorsal-fin height, 3.04 (2.68–2.79) times base of first dorsal-fin, 1.94 (1.66–1.77) times interspace between second dorsal-fin insertion and upper origin of caudal fin. Caudal fin small, dorsal caudal margin 2.13 (1.97–2.19) times preventral margin length. Mature clasper slender, relatively short, inner length of right clasper about 13% TL (left malformed in holotype); tip acute, glans weakly expanded.

Dermal denticles minute, close-set, covering entire body; posterior portions of dorsal and caudal fins naked; thorns and tubercles absent; dorsal surface with narrow series of slightly enlarged, flat-top denticles around eye, along midline, and on scapular; these denticles most pronounced before eye and in nuchal and prenuchal regions; preorbital patch strongly demarcated from those covering orbit.Ventral surface uniformly covered in minute denticles, including upper lip edges, near insertion of anterior nasal flap, below posterolateral and posterior nasal flaps, and on tail beneath pelvic fins, and most of claspers.

Prebranchial sensory pore patch relatively narrow, extending posteriorly to level of first gill slit. Postscapular sensory canal long, not undulated anteriorly, terminating about an eye diameter from pectoral-fin insertions; canal deeply embedded, not forming shallow groove; sensory pores originating anteriorly from very short branches derived from main canal, pores becoming confluent with canals posteriorly.

Rostral cartilage broad, relatively short, length about 61% of length of neurocranium; rostral appendix expanded, broadly rounded apically, posterior margin long, weakly concave. Precerebral anterior fontanelle broad, extending forward from just posterior to rostral base to rostral appendix; dorsal edges of fontanelle well defined, widely separated, almost parallel; ventral edges almost united anteriorly, more constricted than dorsal edges; cranial roof with small oval posterior fontanelle, located well behind precerebral fontanelle. Nasal capsules moderately large, their transverse axes anterolaterally directed; width across nasal capsules 1.20 times nasobasal length of cranium (base of rostrum to occipital condyles); length of nasal capsule about equal to its width; basal plate narrow, its minimum width 4.52 times in nasobasal length. Antorbital cartilage subtriangular, short; junction with nasal capsule broad, posterolateral; lateral extension short, equal to or shorter than length of nasal aperture; apex blunt, margin truncate to concave, without anterior process. Postorbital process well developed, bifurcate, posterior extension very pronounced, width across process 1.51 times in nasobasal length; preorbital process well developed.

Pectoral skeleton with 29–31 (25–31, in 10 paratypes) propterygial, 6 (6–8) mesopterygial, 1 (1–3) neopterygial, 25–27 (25–27) metapterygial, 61–65 (59–65) total radials; anterior radials of propterygium extending forward of nasal capsules by about 10.5% of rostral length. Total pelvic radials 1+24+1; first greatly enlarged, on puboischiadic bar; 24 basipterygial radials; clasper calcified. Vertebral column with 181 (175–185) total centra (synarcual and free), 168 (162–171) post-synarcual centra; 13 (12–16) synarcual centra; 23 (23–26, mainly 23–24) monospondylous centra, only last centrum of holotype without ribs; 101 (98–105) diplospondylous precaudal centra, 44 (39–45) diplospondylous caudal centra.

Live coloration. Body pale yellowish brown dorsally, with dense cover of faint dusky blotches (blotches sometimes absent or more golden in paratypes); somewhat paler near hind margin of pectoral fin; paler yellowish to white on lateral snout, anterior edge of orbit, lateral cutaneous fold of tail, and between ridges of rostral cartilage; nasal capsules not sharply demarcated from lateral snout; snout tip and fins plain. Ventral surface uniformly white; no dark tip on snout apex.

Size. To at least 595 mm TL; males mature at 460 mm but immature at 376 mm TL.

Etymology. In acknowledgment of the efforts of Dr Keith Sainsbury who planned and managed the initial trawl fish surveys of the continental shelf of northwestern Australia. His foresight in recognizing the need for documenting the fauna before attempting to address more management oriented questions is exemplary. This pioneering research has provided an excellent regional biological baseline that would otherwise be unavailable for regional marine management. Goldeneye shovelnose ray is the most regularly used common name.

Distribution. Known from northern and northwestern Australia, from the Timor Sea (NW of Melville Island, Northern Territory) south to the Monte Bello island group (North-West Shelf) in 66–200 m but mostly collected shallower than 150 m.

Remarks. Rhinobatos sainsburyi was initially identified as two unspecified species of Rhinobatos based on colour differences in two field guides (Gloerfelt-Tarp & Kailola, 1984; Sainsbury et al., 1985). Some individuals are spotted and others are plain but there are no other obvious morphological differences between these forms and intermediate colour patterns exist.

This species belongs to a poorly defined subgroup of the genus Rhinobatos Linck characterized by having widely separated, submarginal insertions of the anterior nasal flap, and the dorsal ridges of the rostral cartilages rather well separated and subparallel to each other. This group, which includes the type species of the genus, R. rhinobatos (Linnaeus) , is represented in the Indian Ocean by five species, R. rhinobatos , R. annandalei Norman , R. lionotus Norman , R. holcorhynchus Norman , and R. punctifer Compagno & Randall , and in the western Pacific Ocean by three species, R. schlegelii Müller & Henle , R. formosensis Norman , and R. hynnicephalus Richardson. Recent studies (Last and others, unpublished) suggest that additional undescribed species exist in the region and the ranges of nominal taxa are smaller than first thought.

The body shape of Rhinobatos sainsburyi is distinct within the group. Of related species, using Norman’s (1926) key, it is closest to R. hynnicephalus from the Japanese Archipelago, in having a snout length between 2.3–3.0 (2.5– 2.6 in R. sainsburyi ) times interspiracular distance, preoral length 2.8–3.0 (2.9–3.3) times width of mouth, small inner spiracular fold, disc with rudimentary denticles, and being pale brownish dorsally. It differs significantly, from similarsized specimens of R. hynnicephalus from Japan and Taiwan (HUMZ 34844, 66224, 109478) in having a shorter snout (in adults, 13.1–13.9% vs 1 5.0–16.2% TL), shorter predorsal distance (53.5–55.8% vs 57.3–60% TL), and dorsal-fins relatively more widely spaced (base of pelvic fin to origin of first dorsal-fin 0.7–0.8 vs 1.0–1.2 times interdorsal distance).

ACKNOWLEDGMENTS. Most of the type specimens were obtained from research cruises of the RV Soela between 1980 and 1987. Several vessel crew members and scientists, from Australian museums and the CSIRO Division of Fisheries , contributed to their assembly. The first comprehensive work on these fishes was undertaken as part of a grant from the former Fishing Industry Research and Development Trust (now the Fisheries Research and Development Corporation) to produce an identification guide to the shark and ray fauna of Australia. I thank the co-author of this publication, Dr J. Stevens, for his input and comments on this manuscript. Images were scanned and etched by D. Gledhill. Mr S. Riddoch radiographed material and assisted with counts. Collection information was verified by A. Graham .

Figures

Fig. 3. Ventral view of the snout of the holotype of Rhinobatos sainsburyi n.sp. (CSIRO H.4041-04).

Fig. 4. Radiograph of the chondrocranium of the holotype of Rhinobatos sainsburyi n.sp. (CSIRO H.4041-04).