Acroteriobatus andysabini, Weigmann & Ebert & Séret, 2021

Weigmann, Simon, Ebert, David A. & Séret, Bernard, 2021, Resolution of the Acroteriobatus leucospilus species complex, with a redescription of A. leucospilus (Norman, 1926) and descriptions of two new western Indian Ocean species of Acroteriobatus (Rhinopristiformes, Rhinobatidae), Marine Biodiversity 51, pp. 1-30 : 3-10

Acroteriobatus andysabini sp. nov. Weigmann, Ebert & Séret

http://zoobank.org/ 0D7EA76E-5268-47D2-882B-866E9FA8BAE4

(Malagasy blue-spotted guitarfish)

( Figs. 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , and 13, Table 1)

Rhinobatus annulatus ― Fourmanoir (1963: 35).

Rhinobatos annulatus ― Maugé (1967: 217).

Acroteriobatus leucospilus ― Fricke et al. (2018: 23).

Acroteriobatus leucospilus ― Ghilardi et al. (2019).

The holotype and seven paratypes are deposited in the South African Institute for Aquatic Biodiversity ( SAIAB); three paratypes in the Muséum national d’ Histoire naturelle, Paris ( MNHN); two paratypes in the American Museum of Natural History, New York ( AMNH); and one paratype in each of the California Academy of Sciences ( CAS) and National Museum of Natural History, Smithsonian Institution, Washington D.C. ( USNM).

Holotype SAIAB 97396 , 565 mm TL (fresh), 550 mm TL (after preservation), juvenile male, Douane Beach , Fort Dauphin , Anosy, southeastern Madagascar, 25° 1.651′ S, 46° 59.736′ E, collectors E. Heemstra, T. Razafimanambina, and P.C. Heemstra, 27 April 2010.

Paratypes (14) SAIAB 189672 , 200 mm TL (after preservation), juvenile male, Secteur de Fort Dauphin , southeastern Madagascar, 25° 5.5′ S, 47° 5.5′ E, 69–70 m depth, FV NOSY BE 11, station CP 3569, beam trawl, 8 May 2010 ; SAIAB 189683 , 178 mm TL (after preservation), juvenile male, Secteur de Fort Dauphin , southeastern Madagascar, 25° 4.7′ S, 47° 3.4′ E, 64–65 m depth, FV NOSY BE 11, station CP 3568, beam trawl, 8 May 2010; SAIAB 189815 (2 specimens), 215 mm TL (after preservation), juvenile male and 345 mm TL (after preservation), juvenile female, Secteur de Fort Dauphin , southeastern Madagascar, 25° 14.6′ S, 47° 9.1′ E, 79–80 m depth, FV NOSY BE 11, station CP 3510, beam trawl, 29 April 2010; SAIAB 189816 , 602 mm TL (fresh), 595 mm TL (after preservation), juvenile male, Sud-Ouest Cap Andavaka, southeastern Madagascar, 25° 16.9′ S, 46° 31.3′ E, 53–54 m depth, FV NOSY BE 11, station CP 3549, beam trawl, 4 May 2010; SAIAB 189943 , 195 mm TL (after preservation), juvenile male, Secteur de Fort Dauphin , southeastern Madagascar, 25° 6.6′ S, 47° 6.9′ E, 75 m depth, FV NOSY BE 11, station CP 3570, beam trawl, 8 May 2010; SAIAB 205733 , 191 mm TL (after preservation), juvenile male, Secteur de Fort Dauphin , southeastern Madagascar, 25° 8.3′ S, 47° 9.1′ E, 77 m depth, FV NOSY BE 11, station CP 3571, beam trawl, 8 May 2010; CAS-ICH 247251 (ex SAIAB 192245 ), 340 mm TL (fresh), 325 mm TL (after preservation), juvenile male, off southeastern Madagascar, 25° 3.16′ S, 47° 4.41′ E, ACEP08 - 352/ASCLME survey, trawl 13, collector J. Escobar, depth of capture 69 m, 8 September 2008; MNHN 1929 -223, 603 mm TL, juvenile female, collected between Tuléar (Toliara) and Ankilibe, southwestern Madagascar, collector G. Petit; MNHN 1985 -231, 318 mm TL, juvenile male, Toliara, southwestern Madagascar; MNHN 1989 -553, 466 mm TL, juvenile male, Fort Dauphin (Tôlanaro), southeastern Madagascar; AMNH 232484 , 265 mm TL, juvenile male, field number PD-00-XII- 11 MAD, off northeastern Madagascar, Antongil Bay, Ambodipaka , 16° 4.59′ S, 49° 37′ E, local fishermen, P. Doukakis & Mananjo, 11 December 2000; AMNH 232511 , 361 mm TL, juvenile female, field number PD-01-III-27 MAD, off northeastern Madagascar, Antongil Bay, Rantohely , 15°38.59′ S, 49° 39′ E, local fishermen, P. Doukakis, 27 March 2001; USNM 171058 , ~ 177 mm TL, male embryo, Madagascar, FV NOSY BE, collector J. Millot, March 1955.

Diagnosis

Alarge Acroteriobatus species distinguished by the following combination of characters: dorsal surface smooth, without prominent thorns or tubercles, except for enlarged granular denticles partially around orbital rims and irregularly distributed along midline from nape to somewhat anterior to first dorsal-fin origin; absent between dorsal fins and upper caudal fin. Snout semi-translucent with elongated bluish-gray spots giving “stripe-nosed” appearance, numerous small bluishgray spots covering disc and pectoral, pelvic, dorsal, and caudal fins on a brown background with larger, slightly darker, indistinct brown spots covering the tail and fin bases; outer edges of pelvic-fin margins white, lateral tail folds striped orange and white; ventral surface white, except for a V-shape patternof faint to dark speckledblack spots onsnout tip. Nasal lamellae 42–48; upper jaw tooth row count ~80–87; 179–185 post-synarcual centra; 195–200 total vertebral segments; 64– 68 total pectoral skeleton radials.

Description of the holotype

Values of the eight paratypes at SAIAB and CAS, as well as the two larger paratypes at MNHN in parentheses, more complex differences are described separately. Where relevant, ratios are based on horizontal measurements unless otherwise stated. Detailed morphometric measurements and meristics of the holotype, eight paratypes at SAIAB and CAS, and the two larger paratypes at MNHN are given in Table 1.

External morphology ( Figs. 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , and 10) Disc wedge-shaped, narrowly angular anteriorly, snout angle in front of eyes 79.1° (76–84.6°); anteriormargin undulate, outer pectoral margin broadly rounded, posterior margin convex, rear tip broadly rounded; disc length 1.22 (1.13–1.24) times its width. Pelvic fins elongate, short-based, base length 1.82 (0.82–1.76) times inner margin length; pelvic-fin total length 1.55 (1.43–2.13) times base length, 2.29 (1.95–3.96) times width; anterior margin weakly concave anteriorly, becoming convex posterior to constriction at the level of first propterygials, turning to weakly concave posterior to the level of posterior margin of spiracles and again becoming weakly convex towards broadly rounded apex, posterior margin weakly convex, free rear tip narrowly rounded. Tail elongate, becoming slender, tapering weakly to caudal; depressed, in cross section rounded above, nearly flat below; tail length from anterior cloaca 1.47 (1.29–1.81) times precloacal length, 1.43 (1.25–1.64) timesdisc length, and 5.95 (4.28–6.42) times body width at pelvic-fin insertions; body width 2.2 (2.25– 3.22) times depth at pelvic-fin insertions, 2.41 (2.5–3.17) at first dorsal-fin origin, 2.23 (1.58–2.5) at second dorsal-fin origin. Dermal fold lateral along tail, its origin just posterior to pelvic-fin insertion, extending to just behind the ventral origin of caudal-fin; fold well developed, maximum width at interdorsal space slightly more than the width of posterior nasal flap ( Figs. 1 , 2 , and 3).

Head moderately elongate, ventral length 25.3 (25.2– 29.8)% TL, dorsal length 24.2 (25.7–33.5)% TL; snout rather short, bluntly pointed, preoral length 2.44 (2.00–2.62) times mouth width, 4.88 (3.75–4.89) times internarial distance, 1.15 (1.05–2.27) times dorsal caudal-fin margin, 2.86 (2.27–2.9) times distance from nostril to margin of disc; direct preorbital snout length 2.38 (1.92–2.39) times interspiracular distance, 4.06 (2.9–4.09) times orbit diameter, 3.63 (3.09–3.63) times skeletal interorbital space; interorbital space weakly concave, relatively broad; eyes moderately large, slightly elevated, but not protruding, orbit diameter 1.7 (0.92–2.5) times spiracle length, 0.89 (0.85–1.13) times skeletal interorbital distance. Spiracles relatively large, narrowly bean-shaped; two prominent and strongly compressed folds on upper posterior margin, length of inner spiracular fold 0.7 (0.5–0.7) times that of outer fold; distance between bases of folds 0.5 (0.3–0.7) times length of shortest fold ( Figs. 4 , 5 , and 6).

Nostril moderate large, oblique, all nasal flaps well developed; anterior aperture subcircular; nostril length 3.14 (2.6– 3.83) times anterior aperture width, 1.22 (0.95–1.6) times anterior nasal-flap base length, 0.76 (0.53–0.77) times distance from nostril to edge of disc, 1.29 (1.0–1.28) times internarial distance. Anterior nasal-flap base greatly extended, penetrating horizontally into internarial space, mesial edges barely separated (by about width of posterior nasal flap); innermost extension of flap not narrow; flap base length 1.80 (1.6–2.6) times its width at process, 2.57 (1.67–3.28) times anterior aperture width; minimum distance between mesial insertions of flaps 7.29 (4.8–13.0) in greatest distance across nostrils anteriorly, 2.43 (1.6–4.5) in minimum internarial distance; process of flap two or more times as long as wide, narrowing distally to blunt pointed tip, and adjoining with posterolateral nasal flap and anterior aperture posterior margin. Posterolateral nasal flap well developed, lobe-like, broadest medially, length 3.0 (1.22–3.5) times its width; origin slightly posterior to lateral extremity of anterior nasal aperture, with free fold posteriorly extending nearly to the level of anterior nasal flap insertion. Posterior nasal flap well developed, lobelike, base length 1.86 (1.67–3.0) times its width, its inner edge nearly reaching innermost margin of nostril; width 1.0 (1.0– 1.67) times anterior aperture width, 1.4 (1.0–2.0) times posterolateral nasal-flap width ( Figs. 7 , 8 , and 9).

Mouth width 1.55 (1.44–2.0) times nostril length, 6.56 (5.13–6.71) in precloacal length; positioned beneath posterior margin of orbit. Upper jaw slightly convex, upper lip broadly arched; lower lip not pronounced, not separated from oral groove by ridges of strongly corrugated skin; corners of mouth with several strong, short lateral grooves. Teeth arranged in quincunx, small, close-set, rhombic, broad-based with short, bluntly rounded cusp; upper and lower teeth similar in shape and size; ~84 (~80–87) tooth rows in upper and ~79 (~80–87) in lower jaws. Gill openings strongly wavy; length of third gill slit 2.75 (1.93–3.0) in nostril length, 5.5 (4.75–6.67) in distance between fifth gill slits; distance between first gill slits 1.48 (1.3–1.58) times distance between fifth gill slits; distance between fifth gill slits 2.59 (2.22– 2.73) times internarial distance, 1.29 (1.12–1.54) times mouth width, 0.32 (0.29–0.37) of ventral head length ( Fig. 9 ).

Dorsal fins erect, relatively tall, dissimilar in size and shape; first dorsal-fin anterior margin weakly convex, curving rearwards towards rounded apex; posterior margin weakly convex near tip, then becoming weakly concave to nearly straight; second dorsal-fin anterior margin weakly convex, curving rearwards towards pointed apex; posterior margin nearly straight; free rear tips rounded of both dorsal fins, almost forming right angle, not produced; first dorsal fin height subequal to second, length of first 0.93 (0.92–1.44) times height, its base length 2.15 (1.17–2.5) times inner margin length; second dorsal-fin length 1.0 (0.93–1.42) times its height, base length 1.47 (1.34–2.21) times inner margin length ( Fig. 10a, b ). First dorsal-fin origin well posterior to pelvic-fin free rear tips, interspace 1.29 (1.0–1.15) times interdorsal distance; interdorsal space relatively short, 1.48 (1.16–2.09) times second dorsal-fin height, 2.11 (1.88–2.88) times base of first dorsal fin, 1.11 (0.71–1.25) times tail width at origin of first dorsal fin, 1.59 (1.11–1.9) times interspace between second dorsal-fin insertion and upper origin of caudal fin. Caudal fin relatively small; dorsal caudal margin weakly convex, length 1.6 (1.53–2.08) times preventral margin length; ventral lobe broadly rounded; posterior margin weakly concave; fin tip acutely pointed ( Fig. 10c ).

Dermal denticles mostly minute, close-set, covering entire body and fins; surfaces mostly smooth to the touch, except for a continuous row of ~15 to 20 somewhat enlarged granular and smaller denticles around the anterior and inner rim of orbits, extending to the anterior edge of inner spiracle; enlarged, coarse denticles patchily distributed along midline from nape to ~ 50 mm anterior to first dorsal-fin origin, absent along midline between dorsal fins and upper caudal origin; enlarged denticles absent on snout tip, anterior and lateral margins of disc, pelvic fins, and bases of dorsal fins; nasal flaps and lamellae naked. Crowns of denticles mostly oval, except largest denticles with slightly erect, bluntly acute cusp, base stellate. Thorns absent. Prebranchial sensory pore patch distinct, extending to just behind the level of third gill slit. Post-scapular sensory canal rather indistinct, weakly undulated anteriorly, terminating near pectoral-fin insertions; sensory pores minute, canal not forming a shallow groove ( Fig. 3 ).

Rostral cartilage broad, its shaft just slightly increasing in width posteriorly from rostral node; rostral node rounded at apex, not angular, broadly expanded, relatively short, axis at maximum node width 34.1 (33.6–39.3)% of length of rostral cartilage from tip; anterior fontanelle relatively broad posteriorly, tapering gradually towards rostral node, dorsolateral edges of cartilage surrounding fontanelle (rostral ridges on surface of snout) well separated posteriorly, not constricting medially; rostral cartilage 57.5 (52.6–57.1)% of neurocranium length, ventral edges of rostral cartilage united; nasal capsules large, with their transverse axes directed anterolaterally; width of cranium across nasal capsules 1.25 (1.17–1.27) times nasobasal length (base of rostrum to occipital condyles); width of nasal capsule 1.79 (1.56–1.87) times its length; basal plate relatively broad, its minimum width 3.37 (3.15–3.75) times in nasobasal length; cranial roof with small, oval-shaped fenestra, with its anterior edge located behind precerebral cavity by a distance ~1.5 times its length; anterior cartilage triangular, narrow, posteriorly wedge-shaped, without an anterior lobe extending past nasal capsules; preorbital processes well developed; postorbital processes moderately large, not bifurcate; greatest width across processes 1.91 (1.79–1.99) times in nasobasal length ( Fig. 11 ).

Nasal lamellae 45 (42–48). Pectoral skeleton with 32 (30– 32) propterygial, 9 (8–10) mesopterygial, 2 (1–2) neopterygial, 25 (24–25) metapterygial, amounting to 68 (64–68) total radials. Total pelvic-fin radials 25 (24–27). Total vertebral segment (synarcual and free) counts 196 (195–200); post-synarcual centra 180 (179–185); precaudal centra (excluding synarcual centra) 139 (137–144); synarcual segments 16 (14–17); monospondylous precaudal centra 39 (37–42); diplosondylous precaudal centra 100 (98–104); diplosondylous caudal centra 41 (40–42). Monospondylous to diplosondylous centra transition posterior to pelvic girdle.

Coloration

Prior to preservation: dorsal surface light to medium brown with an orangish tinge, an organized pattern of smaller bluishgray circular spots, with a darker ring encircling a lighter bluish-gray center, and indistinct larger brownish spots ( Figs. 1 and 4 ); smaller bluish-gray spots cover thesnout, disc, pectoral, pelvic, dorsal, and caudal fins; larger brownish spots mostly coverthetail andfin bases, but not extending onto fins; snout semi-translucent with somewhat elongated bluish-gray spots giving it a stripe-nosed appearance ( Figs. 1 , 4 , and 12). Outer edges of pelvic-fin margins white, outer edges of posterior dorsal-fin margins translucent whitish, lateral tail folds striped orange and white. Ventral surface mostly white, except for faint to dark speckled black spots forming a V-shape on rostral snout tip; spots becoming darker and more numerous with growth ( Fig. 7 ); in small (≤ 215 mm TL), newborn specimens short V-shaped black lines with faint dark spots at base extending from tip to about one-third snout length to midpoint of internostril space; larger individuals (> 300 mm TL) with prominent dark to black spots, becoming more numerous and with spots extending to about the midpoint of rostrum; pectoral and pelvic fins mostly white, except fin edges brownish ( Fig. 7 ). After preservation: dorsal surface similar but bluish-gray spots less pronounced and large brownish spots mostly faded and not evident ( Fig. 2 ). Ventral surface also similar, except edges of pectoral and pelvic-fin margins fade to a lighter brown ( Fig. 3 ).

Size

The new species is described from 15 specimens (ten males and five females), ranging in size from 177 to 603 mm TL. All types are juvenile, the size at birth is ~ 180 mm TL. Based on images of unretained specimens ( Fig. 12 ), Acroteriobatus andysabini sp. nov. is a large species of Acroteriobatus growing to more than 1000 mm TL.

Distribution

Acroteriobatus andysabini sp. nov. is presently only known from the coastal waters surrounding Madagascar and may be endemic to this region ( Fig. 13 ). Records are from off Tôlanaro, Anosy region, and Cape Andavaka (southeastern Madagascar), Toliara and Ankilibe (southwestern Madagascar), and Antongil Bay (northeastern Madagascar). Its depth range is from shallow coastal waters to at least 80 m. Fricke et al. (2018) reported A. leucospilus as anew species record for Madagascar but commented that the species had been misidentified previously as Rhinobatos (= Acroteriobatus ) annuulatus by several earlier authors.

Etymology

The species name andysabini is in honor of Andy Sabin for his gracious support of the Lost Sharks project at the Pacific Shark Research Center.

Figures

Fig. 1 Acroteriobatus andysabini sp. nov., SAIAB 97396, juvenile male holotype, 565 mm TL fresh, in total dorsal view taken directly after catching. Photograph by Elaine Heemstra, NRF-SAIAB

Fig. 2 Acroteriobatus andysabini sp. nov., SAIAB 97396, juvenile male holotype, 550 mm TL, in total dorsal view. Scale bar: 5 cm. Photograph courtesy Marsha Englebrecht ©

Fig. 3 Acroteriobatus andysabini sp. nov., SAIAB 97396, juvenile male holotype, 550 mm TL, in total ventral view. Scale bar: 5 cm. Photograph courtesy Marsha Englebrecht ©

Fig. 4 Acroteriobatus andysabini sp. nov., SAIAB 97396, juvenile male holotype, 565 mm TL fresh, head in dorsal view taken directly after catching. Photograph by Elaine Heemstra, NRF-SAIAB

Fig. 5 Acroteriobatus andysabini sp. nov., SAIAB 97396, juvenile male holotype, 550 mm TL, head in dorsal view. Photograph courtesy Marsha Englebrecht ©

Fig. 6 Acroteriobatus andysabini sp. nov., SAIAB 97396, juvenile male holotype, 550 mm TL, close-up of orbital and spiracular region. Photograph courtesy Marsha Englebrecht ©

Fig. 7 Acroteriobatus andysabini sp. nov., SAIAB 97396, juvenile male holotype, 565 mm TL fresh, head in ventral view taken directly after catching. Photograph by Elaine Heemstra, NRF-SAIAB

Fig. 8 Acroteriobatus andysabini sp. nov., SAIAB 97396, juvenile male holotype, 550 mm TL, head in ventral view. Photograph courtesy Marsha Englebrecht ©

Fig. 9 Acroteriobatus andysabini sp. nov., SAIAB 97396, juvenile male holotype, 550 mm TL, close-up of mouth-nasal region. Photograph courtesy Marsha Englebrecht ©

Fig. 10 Acroteriobatus andysabini sp. nov., SAIAB 97396, juvenile male holotype, 550 mm TL; first dorsal (a), second dorsal (b), and caudal (c) fins in lateral views (c image reversed). Photographs courtesy Marsha Englebrecht ©

Fig. 11 Acroteriobatus andysabini sp. nov., SAIAB 97396, juvenile male holotype, 550 mm TL, radiograph of cranium and snout in dorsal view. The radiograph was taken and kindly provided by Jon Fong

Fig. 12 Acroteriobatus andysabini sp. nov., Malagasy artisanal fisherman with large (~1000 mm TL) specimen. The photograph was taken and kindly provided by Kerry Sink

Fig. 13 Map of the southwestern Indian Ocean depicting the catch locations of the examined specimens of all three species of the Acroteriobatus leucospilus species complex. Holotype (white star) and paratypes (white circles) of A. andysabini sp. nov., holotype (gray star) and paratypes (gray star and gray circle) of A. stehmanni sp. nov., and syntypes (black triangles) and other specimens (black squares) of A. leucospilus