Rhinobatos borneensis Last, Séret & Naylor, 2016, sp. nov.
Creators: name: Last, Peter R.
name: Séret, Bernard
name: Naylor, Gavin J. P.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Elasmobranchii
Rajiformes
Rhinobatidae
Rhinobatos
Rhinobatos borneensis

description: Rhinobatos borneensis sp. nov.
(Figs. 2–9, Table 1)
Rhinobatos formosensis (not Norman, 1926): Last et al., 2010, 158–159, figs.
Holotype. SMEC 373 (field numbers PLMM 1, MMKK 1-51109), adult male 633 mm TL, Kota Kinabalu fish market (05°58'57.66"N, 116°04'19.83"E), Sabah, Malaysia, 5 November 2009.
Paratypes. 9 specimens: 7 collected with holotype: IPMB-I 0 1.00115 (field numbers PLMM 2, MMKK 2- 51109), adult female 829 mm TL; CSIRO H 7086–01 (4 of 7), 2 prenatal juvenile males 187–189 mm TL and 2 females 189–190 mm TL, from mother IPMB-I 01.00115; SMEC 374 (field number PLMM 3, MMKK 3-51109), adult female, 900 mm; IPMB-I 0 1.00117 (field number PLMM 4, MMKK 4-51109), female, 643 mm. CSIRO H 7543–01 (field number BO 350), adult male 651 mm TL, Kota Kinabalu fish market (05°58'57.66"N, 116°04'19.83"E), Sabah, Malaysia, 5 May 2004; CSIRO H 7544–01 (field number BO 537), adult male 686 mm TL, Kota Kinabalu fish market (05°58'57.66"N, 116°04'19.83"E), Sabah, Malaysia, 14 Aug 2004.
Other material. IPMB-I 0 1.00120, 5 additional prenatal juveniles from mother IPMB-I 01.00115; FBC Sarawak unreg (field number BOD 39), female ~ 900 mm TL, Tanjung Manis fish market (02°07'07.04"N, 111°19'37.16"E), Sarawak, Malaysia, 7 June 2004.
Diagnosis. A species of the genus Rhinobatos distinguished by the following combination of characters in adults: wedge-shaped disc, width 29–31% TL, disc length 1.30–1.42 times width; snout length 2.5–3.3 times interspiracular distance, 3.8–5.6 times interorbital width; medium-sized orbit, 1.5–2.2 times spiracle length; weakly oblique nostrils, their length 1.5–1.7 times internarial distance; preoral length 7.4–8.1 times internarial distance; anterior nasal flaps penetrating slightly into internarial space but well separated at their insertion (not reaching level of inner corner of nostril); posterior nasal flaps broad; two spiracular folds, outermost fold distinctly taller than inner fold; ridges of rostral cartilage almost parallel, converging slightly anteriorly but not constricted medially; anterior cartilage sickle shaped, pointed or blunt posteriorly; distance between fifth gill slits 2.7–3.3 times in ventral head length; prebranchial sensory pore patch obvious, extending to just behind first gill slit; postscapular sensory canal obvious, with exposed lateral pores, grooved; thorn patches on supraorbit, scapular region, and dorsal midline rudimentary, not conspicuous; pelvic-fin inner margin subequal to its base in males, shorter in females; interdorsal distance 2.5–3.3 times first dorsal-fin base; dorsal caudal margin 1.9–2.3 times preventral margin; upper jaw with ca. 90 tooth rows; 176–180 post-synarcual centra; 50–53 nasal lamellae; dorsal fin usually with a large, often faint, central dusky blotches; dorsal disc of adults yellowish or brownish, often with diffuse pale yellowish blotches, without white spots; young with ocellate markings.
Description. Disc broadly wedge shaped, angular anteriorly, angle before eyes 56–57o in two paratypes (CSIRO H 7543-01 and H 7544-01), 61–63o in four late-term embryos (CSIRO H 7086–01); outer margins broadly rounded, narrowly rounded distally; its length 1.37 in holotype (1.30–1.42 in all paratypes) times width. Pelvic fins elongate, short-based, base length 0.91 (0.98–1.03 in adult male paratypes, 1.17–1.44 in female paratypes) of inner margin length; total length 2.09 (1.91, 1.66–1.79) times their base length, 2.60 (2.52–2.71, 2.44–2.56) times width; anterior margin weakly concave anteriorly then becoming straight to weakly convex, apex broadly rounded, posterior margin almost straight. Tail moderately elongate, slender anteriorly, tapering weakly; in cross-section nearly flat below, rounded above; tail length from anterior cloaca 1.45 (1.43–1.51, 1.39–1.44) times precloacal length, 1.45 (1.38–1.50) times disc length, 5.78 (6.00–6.08, 5.46–5.72) times its width at pelvic-fin insertions; tail width 2.29 (2.23–2.66) times depth at pelvic-fin insertions, 2.50 (2.43–2.73) at first dorsal-fin origin, 2.04 (2.03– 2.55) at second dorsal-fin origin. Dermal fold lateral on tail, originating well behind free rear tip of pelvic fin, reaching just behind ventral caudal-fin origin; fold moderately well developed, maximum width at interdorsal space slightly more than half width of posterior nasal flap.
Head moderately elongate, ventral length 27.4 (24.4–28.0)% TL; snout moderately long and bluntly pointed; preoral length 3.48 (3.07–3.38) times mouth width, 7.55 (6.96–7.54, 7.36–8.06) times internarial distance, 1.40 (1.24–1.42) times dorsal caudal-fin margin, 5.65 (5.96–6.22, 5.22–5.61) times distance from nostril to margin of disc; preorbital snout length (direct) 3.10 (2.54–3.28) times interspiracular length, 3.80 (3.06–4.43) times orbit, 5.58 (3.82–5.35) times interorbital width; interorbital space almost flat, rather broad; eyes moderately large, not elevated or protruding, orbit relatively small, diameter 1.80 (1.49–2.19) times spiracle length, 1.47 (1.14–1.30) times interorbital distance. Spiracles narrowly bean-shaped, relatively large; two strongly compressed folds on upper posterior margin, length of innermost spiracular fold 0.6–0.8 of outer fold; distance between bases of folds about 0.7–1.0 length of shortest fold. Nostril moderately large, oblique, nasal flaps well developed; anterior aperture suboval, width slightly exceeding length; nostril length 3.32 (3.00–3.21) times anterior aperture width, 1.63 (1.40–1.67) times anterior nasal-flap base length, 1.11 (1.22–1.29, 1.03–1.10) times distance from nostril to edge of disc, 1.48 (1.45–1.68) times internarial distance. Anterior nasal flap moderate with long, slender process anteriorly; flap base length 1.53 (1.48–1.58, 1.64–1.74) times its width at process, 2.03 (1.81–2.16) times anterior aperture width; inserted well into internarial space; distance between insertions of flaps 3.21 (3.29–3.63) in greatest distance across nostrils anteriorly, 0.91 (0.91–1.06) in minimum internarial distance; process of flap about twice as long as wide, bluntly pointed distally, abutting posterolateral nasal flap and determining hind margin of anterior aperture. Posterolateral nasal flap lobe-like, broadest medially, length 4.77 (4.42–5.39) times width; originating just behind lateral extremity of anterior nasal aperture, extending posteromedially as a free fold almost to level of insertion of anterior nasal flap. Posterior nasal flap strongly lobe-like, base length 2.17 (1.75–2.87) times its width, its inner edge well short of innermost margin of nostril; width 0.94 (0.70–1.00) times anterior aperture width, 1.65 (1.35–1.79) times posterolateral nasal-flap width. Mouth width 1.47 (1.50–1.65) times nostril length, 7.50 (7.10– 7.24, 7.47–7.65) in precloacal length; positioned slightly forward of hind margin of orbit. Upper jaw weakly convex, upper lip arched slightly; lower lip pronounced, separated from oral groove by ridges of strongly corrugated skin; strong, short lateral grooves around corners of mouth. Teeth small, blunt, crowns rhomboidal with weak, pointed posterior cusps; teeth quincuncial, in ~90–91 rows in upper jaw; upper and lower jaw teeth similar in shape and size. Gill openings s-shaped, fifth less so; length of third gill slit 2.65 (2.18–2.82) in nostril length, 6.06 (5.85–6.39) in distance between fifth gill slits; distance between first gill slits 1.43 (1.41–1.43, 1.31–1.40) times distance between fifth gill slits; distance between fifth gill slits 3.38 (3.17–3.54, 3.59–4.22) times internarial distance, 1.56 (1.46–1.67) times mouth width, 0.31 (0.30–0.37) of ventral head length.
Dorsal fins rather short; apices narrowly rounded to angular; anterior margins weakly convex; posterior margins straight to weakly concave; free rear tips almost forming right angle, barely produced; first dorsal fin slightly taller and more upright than second, length of first 0.94 (0.89–0.97) times its height, base length 2.11 (1.61–2.33) times inner margin length; second dorsal-fin length 1.19 (1.07–1.10, 0.97–1.06) times its height, base length 2.50 (2.03–2.65) times inner margin length. First dorsal fin well behind pelvic-fin insertion, interspace 0.90 (0.80–0.97) times interdorsal distance; interdorsal space moderate, 2.25 (2.29–2.31, 1.76–1.93) times second dorsal-fin height, 2.82 (2.51–3.25) times base of first dorsal fin, 1.36 (1.44–1.48, 1.28–1.34) times tail width at origin of first dorsal fin, 1.68 (1.70–1.94, 1.57–1.69) times interspace between second dorsal-fin insertion and upper origin of caudal fin. Caudal fin relatively small, deep and short; dorsal caudal margin 2.26 (1.92–2.18) times preventral margin length.
Dermal denticles small, closely set, covering entire body and fins; surfaces uniformly coarsely granular, becoming enlarged slightly along dorsal midline, and on orbital and spiracular rims; enlarged slightly on midline of tail between dorsal fins, precaudal midline, snout tip, and lateral margin of disc anteriorly; dense covering of minute denticles over nasal lamellae; crowns of smallest denticles tricuspidate anteriorly, forming acute angle posteriorly; largest denticles with median ridge bulbous anteriorly with longitudinal furrows. Thorns very small or rudimentary, sometimes partly embedded or with scar remaining when absent; cusps of largest thorns relatively low, bluntly rounded distally, rarely with sharp rear angle, base stellate; weak around orbit, most pronounced on preorbit and near inner margin of spiracle, barely evident without magnification; similar band on dorsal midline, variable in shape and size; largest denticles somewhat globular, in a single semi-regular row; scapular patches with slightly enlarged embedded denticles, or weak thorns. Prebranchial sensory pore patch distinct, extending to just behind level of first gill slit. Postscapular sensory canals embedded, weakly undulated anteriorly, terminating about an eye diameter forward of pectoral-fin insertions; sensory pores evident; sensory canal not forming a shallow groove.
Rostral cartilage broad, its shaft increasing in width initially and then only slightly in a posterior direction; rostral node broadly expanded and elongate, rounded apically, not angular, axis at widest part of node ~26.3% of length of rostral cartilage from snout tip (paratype CSIRO H 7544–01); precerebral cavity relatively broad posteriorly, converging to a point anteriorly at rostral node, dorsolateral edges of cartilage surrounding cavity (rostral ridges on surface of snout) well separated posteriorly, not constricted medially; rostral cartilage ~67% of length of neurocranium, ventral edges of rostral cartilage united; nasal capsules large, their transverse axes anterolaterally directed; maximum width across capsules ~1.31 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 ~4.42 times in nasobasal length; cranial roof with small oval fenestra, located behind precerebral cavity by a distance slightly exceeding its length; anterior cartilage narrowly triangular, sickle shaped, posterior apex truncated or bluntly pointed, without an anterior lobe extending beyond nasal capsules; preorbital processes short, angular; postorbital processes well developed, weakly bifurcate, posterior process most pronounced; greatest width across processes ~1.5 times in nasobasal length.
Meristics based on paratypes CSIRO H 7543-01, H 7544-01: Nasal lamellae 50–53. Pectoral skeleton with 30– 31 propterygial, 7–9 mesopterygial, 1–2 neopterygial, 25–27 metapterygial, 66–67 total radials. Total pelvic-fin radials 25 in males excluding clasper. Vertebral column with 188–191 total segments (synarcual and free), 176–180 post-synarcual centra; 131–133 precaudal centra (excluding synarcual centra); 11–12 synarcual segments; 25 monospondylous precaudal centra; 106–108 diplospondylous precaudal centra, 45–47 diplospondylous caudal centra.
Colour. Adult male holotype (when fresh): medium brownish on dorsal surface of body with scattered pattern of faint greyish brown blotches with diffuse edges; largest blotches similar to size of orbit, smaller than pupil, most obvious anteriorly on body; no rostrum similar to body, snout opposite paler, with distinct blotches, tip darker brownish; evidence of white spots on body; distinctly paler yellowish around margin of disc, pelvic fins, spiracles and along upper lateral skin fold; eyes golden, pupils dark bluish black, orbital membrane similar to coloration of disc; first dorsal fin anterior half and base similar to body, posterior half of fin darker brownish; coloration of second dorsal fin almost identical to first; caudal fin similar to body colour with dark brownish lateral blotch anteriorly and hind quarter of fin dusky. Ventral surface largely white with yellowish brown areas; oronasal region, snout tip and rostrum white, snout opposite dappled brownish; apex and posterior disc, and pelvic-fin margins broadly yellowish, their inner margins diffuse.
Adult female paratype, IPMB-I 0 1.00115 (when fresh), similar in body and fin coloration to adult male holotype, blotches less obvious, except on snout; ventral surface white, with less pronounced darker areas on snout, and along disc and pelvic-fin margins. Prenatal juvenile paratypes (when fresh) greyish green on dorsal surface with dense pattern of faint ocelli; ocelli regular in size (about half eye width), greyish white with slightly darker centres; lateral snout, and margins of disc and pelvic fins semi-translucent; dorsal and caudal fins semi-translucent, each with large black distal spots (additional smaller black spot below main spot on caudal fin in most individuals); ventral surface uniformly semi-translucent or white. In preservative, adults of both sexes becoming yellowish, markings obscure or as pale rusty brown blotches; juveniles also with well-defined pale blotches (replacing ocelli).
Size. A medium-sized Rhinobatos, the type series contains three adult males, 633–686 mm TL, and at least two larger adult females, 829–900 mm TL. One pregnant specimen (PLMM 2, 829 mm TL) had 7 late-term embryos, 187–190 mm TL (based on four paratypes).
Distribution. Known from the South China Sea, off Malaysian Borneo. Collected from fish markets at Tanjung Manis (Sarawak) and Kota Kinabalu (Sabah); presumably caught in nearby waters. Probable bycatch of inshore trawl fisheries and landed more widely in the South China Sea.
Etymology. Named with reference to the type locality (Borneo) from where the first specimens were observed during a UK Darwin Foundation funded survey of the sharks and rays of Sabah in 1996. English common name: Borneo Shovelnose Ray.
Comparisons. Rhinobatos borneensis belongs to a small subgroup of guitarfishes of the genus Rhinobatos that are plain or faintly patterned (rather than being white spotted or with prominent black markings dorsally). The subgroup is thought to include at least three additional nominal species in the Indo –West Pacific: R. jimbaranensis, R. sainsburyi and R. whitei. Two other species of the genus Rhinobatos, R. hynnicephalus and R. schlegelii, also occur in the western sector of this region.
Rhinobatos borneensis was initially thought to be undescribed (PL), but in the absence of molecular support and based on its superficial similarity, was provisionally treated in a guide to the sharks and rays of Borneo as R. formosensis (Last et al., 2010). However, after examining the types of both R. formosensis and R. schlegelii we have concluded that these taxa are morphologically distinct from R. borneensis. Moreover, Norman’s R. formosensis appears to be a junior synonym of R. schlegelii based on its current definition (Séret & Last, unpubl.). However, two distinct morphotypes exist in the type series of R. schlegelii: six of these are clearly conspecific with R. formosensis, but two specimens (including the lectotype) are shorter-snouted guitarfishes and may be another species. The Western North Pacific guitarfish, R. schlegelii, is morphologically distinct from R. borneensis, and this species (along with R. hynnicephalus based on other analyses) forms a subgroup of Rhinobatos, widely divergent from members of the R. borneensis cluster (Fig. 9). The guitarfishes of the western North Pacific have been well sampled and to date only two species (i.e. R. schlegelii and R. hynnicephalus) have been identified from the region using molecular techniques.
Rhinobatos borneensis shares with R. formosensis / schlegelii a largely plain coloration (without a distinctive dorsal pattern of spots and/or rings and lacking the usual dark blotch near the ventral snout apex), long snout with narrow rostral ridges that are well separated throughout their length (rather than a short or moderate snout with median constrictions of the rostral ridges) and rudimentary tubercular denticles along its mid-disc (rather than denticles enlarged slightly and blunt). Based on morphometric data, large males types of Rhinobatos borneensis differ from the two subadult males types of R. formosensis (BMNH 1862.12.6.69-70, 642 and 645 mm TL) in ML tree for ND2 data (GTR +I + Gamma model)
1
Rhinobatos borneensis Sabah Malaysia GN 3605 Rhinobatos borneensis Sarawak Malaysia GN 2906 Rhinobatos whitei Sulu Sea Philippines GN 2244 Rhinobatos whitei South China Sea Philippines GN 4388 Rhinobatos whitei Sulu Sea Philippines GN 2253 Rhinobatos whitei Sulu Sea Philippines GN 2254 Rhinobatos whitei South China Sea Philippines GN 4326 Rhinobatos sainsburyi Northern Territory Australia GN 17247 Rhinobatos sainsburyi Northern Territory Australia GN 17248 Rhinobatos sainsburyi Northern Territory Australia GN 17250 Rhinobatos sainsburyi Northern Territory Australia GN 17251 Rhinobatos sainsburyi Northern Territory Australia GN 17249 Rhinobatos jimbaranensis Indonesia GN 11251
Rhinobatos jimbaranensis Indonesia GN 11253
Rhinobatos jimbaranensis Indonesia GN 11254
Rhinobatos jimbaranensis Indonesia GN 11255
Rhinobatos schlegelii Taiwan GN 6187
0.005 substitutions/site
having: a slightly larger disc (width 28.9–29.8% vs. ~27.3% TL in R. formosensis); more widely separated gills (width between first gill openings 11.7–12.1% vs. 10.9–11.1% TL; between fifth gill openings 8.3–8.5% vs. 7.6– 7.8% TL); larger pelvic fins (length 14.0–14.6% vs. 13.2–13.7% TL); nostril length 1.5–1.7 (rather than ~1.4) in its mouth width; distance from pelvic-fin base to dorsal-fin origin 0.8–1.0 (rather 1.1–1.2) times the interdorsal distance; and the body is noticeably wider (width at anterior orbit 16.1–16.6% vs. 15.0–15.6% TL; at pelvic-fin insertion 9.7–10.3% vs. 9.0–9.2% TL; at first dorsal-fin origin 9.3–9.4% vs. 7.8–8.0% TL; at second dorsal-fin origin 4.7–5.2% vs. 4.0–4.2% TL). Rhinobatos borneensis also appears to have slightly longer and more anteriorly positioned dorsal fins.
Rhinobatos borneensis differs morphometrically from R. whitei which occurs in the nearby Philippines. In adults, its disc is proportionally smaller (disc width 28.9–29.8% in males and 28.8–31.0% TL in females vs. 30.9– 32.6% and 33.5–34.6% TL respectively in R. whitei; disc length 40.0–41.0% in males and 40.3–42.3% TL in females vs. 41.3–43.0% and 43.1–44.0% TL respectively). The interorbital space (2.8–3.3% vs. 3.3–4.0% TL in R. whitei) and the mouth (5.4–5.7% vs. 5.7–6.4% TL) are proportionally wider in R. whitei; and the disc is relatively narrow at the front of orbit (width 16.1–16.6% in adult males vs 17.4–18.7%. TL). Similar trends exist for several other characters: ventral head and preoral lengths, orbit and spiracle length, base length of anterior nasal flap, distance of nostril from edge of disc, and dorsal-fin dimensions; all are proportionally smaller in R. borneensis. Rhinobatos whitei also has white spots but these are lacking in R. borneensis. Differentiation of these species is further supported by molecular data with R. whitei being the possible sister species to R. borneensis (Fig. 9).
Rhinobatos jimbaranensis from Indonesia is similarly plain coloured or with faint rusty brown blotches. However, these species differ in morphometrics with a major difference being the large nostril with a relatively large anterior aperture in R. borneensis (nostril length 1.5–1.7 vs. 1.3–1.4 times internarial distance in R. jimbaranensis; anterior aperture width 1.13–1.26% vs. 0.90–1.10% TL). In adult R. borneensis the disc is proportionally smaller (disc width 28.9–31.0% vs. 31.8–32.8% TL in R. jimbaranensis; disc length 40.0–42.3% vs. 42.8–44.8% TL). Similarly, the dorsal and ventral head, preorbital snout length, preoral and prenarial lengths, pelvic-fin size, and interspaces between the nostrils and gills are all smaller. The dorsal fins are usually more widely separated in R. borneensis and the dorsal and caudal fins located more posteriorly on the body. Differentiation of these species is similarly supported by molecular data.
Trygonorrhina dumerilii GN10794 (Trygonorrhinidae)
Aptychotrema rostrata GN10790 (Trygonorrhinidae) Zapteryx exasperata GN5447 (Trygonorrhinidae) Rhinobatos rhinobatos GN6030 (Rhinobatidae) Acroteriobatus annulatus GN7309 (Rhinobatidae) Pseudobatos glaucostigmus GN5409 (Rhinobatidae) Rhina ancylostoma GN7488 (Rhinidae)
Rhynchobatus laevis GN12249 (Rhinidae) Glaucostegus cemiculus GN3290 (Glaucostegidae) Anoxypristis cuspidata GN2078 (Pristidae) Pristis pristis GN2752 (Pristidae) Zanobatus schoenleinii GN6041 (Outgroup)
0.1 substitutions/site
description: Published as part of Last, Peter R., Séret, Bernard & Naylor, Gavin J. P., 2016, A new species of guitarfish, Rhinobatos borneensis sp. nov. with a redefinition of the family-level classification in the order Rhinopristiformes (Chondrichthyes: Batoidea), pp. 451-475 in Zootaxa 4117 (4) on pages 453-462, DOI: 10.11646/zootaxa.4117.4.1, http://zenodo.org/record/271659