Squalus melanurus Fourmanoir, 1979

Viana, Sarah T. F. L. & De Carvalho, Marcelo R., 2018, Squalus rancureli Fourmanoir, 1979, a new junior synonym of the blacktailed spurdog S. melanurus Fourmanoir, 1979, and updated diagnosis of S. bucephalus Last, Séret & Pogonoski, 2007 from New Caledonia (Squaliformes, Squalidae), Zoosystema 40 (9), pp. 159-177 : 162-168

Squalus melanurus Fourmanoir, 1979

Blacktailed spurdog; Aiguillat à queue noire ( Figs 1-8 , 15 ; Tables 1-2)

Squalus melanurus Fourmanoir, 1979: 11-12 (original description, illustrated. Type by subsequent designation in Fourmanoir & Rivaton (1979). Type locality: Uatio and Boulari, New Caledonia). — Fourmanoir & Rivaton 1979: 438-439, fig. 27 (description, illustrated, designation of type; Uatio and Boulari, New Caledonia). — Compagno 1984: 120 (description; Uation and Boulari, New Caledonia); 2005: 504 (listed). — Rivaton et al. 1990: 72, 134 (listed, New Caledonia). — Séret 1994: 6-8 (cited, listed; New Caledonia). — Séret et al. 1997: 104 (cited; New Caledonia). — Compagno & Niem 1998: 1215, 1222, 1230 (cited, listed; New Caledonia). — Baranes 2003: 45, 49 (cited; New Caledonia). — Trilles & Justine 2004: 1-21 (cited; New Caledonia). — Compagno et al. 2005: 77 (description; Noumea ). — Justine 2009: 1-2 (cited; New Caledonia). — Fricke et al. 2011: 346 (cited; Southwestern Grande Terre , New Caledonia). — Weigmann 2016: 904 (listed; Southwestern Pacific Ocean ). — Bernot & Boxshall 2017: 275-276, 286, 288 (cited, listed; New Caledonia).

Squalus rancureli Fourmanoir, 1979: 11-12 , 14, n. syn. (original description, illustrated. Type by subsequent designation in Fourmanoir & Rivaton (1979). Type locality: Vate , Vanuatu, formerly New Hebrides, and western New Caledonia). — Fourmanoir & Rivaton 1979: 437-438, figs. 25-26 (description, illustrated, type designation; Vate and Espiritu Santo, Vanuatu). — Compagno 1984: 122-123 (description; Vate, Vanuatu); 2005: 505 (listed). — Rivaton et al. 1990: 72, 134 (listed, New Caledonia). — Kulbicki et al. 1990: 17 (listed; Chesterfield Islands , New Caledonia). — Séret 1994: 6-7 (cited, listed; New Caledonia). — Compagno & Niem 1998: 1215, 1222, 1231 (cited; Vanuatu). — Baranes 2003: 45, 49 (cited; Vanuatu). — Compagno et al. 2005: 78 (description; Vanuatu). — Fricke et al. 2011: 346 (cited; New Caledonia). — Weigmann 2016: 904 (listed; Southwestern Pacific Ocean ).

TYPE MATERIAL. — MNHN-IC-1980-0460 (holotype of S. melanurus ), adult ♂, 670 mm TL, New Caledonia, 320-340 meters depth, collected by P. Fourmanoir ( IRD, formerly ORSTOM) on 10.IV.1978 .

MATERIAL EXAMINED. — MNHN-IC-1978-0693 (holotype of S. rancureli ), adult ♂, 680 mm TL, Vate, Vanuatu, 17°30’0”S, 167°30’0”E, collected by P. Rancurel, date unknow ; MNHN- IC-1987-1203 (paratype of S. rancureli ), adult ♀, 640 mm TL, Vate, Vanuatu, 17°30’S, 167°30’E ; MNHN-IC-1987-1204, adult ♀, 675 mm TL, Vate, Vanuatu, 17°55’1.2”S, 167°19’58.8”E ; MNHN-IC-1997-3606, adult ♀, 730 mm TL, unknown locality ; MNHN-IC-1997-3607, adult ♀, 750 mm TL, unknown local- ity ; MNHN-IC-1997-3617, adult ♂, 680 mm TL, New Caledonia, 23°43’1”S, 168°15’0”E ; MNHN-IC-1997-3619, juvenile ♀, 527 mm TL, New Caledonia, 23°43’1”S, 168°15’0”E ; MNHN- IC-1997-3621, adult ♂, 647 mm TL, Norfolk Island, Australia ; MNHN-IC-1997-3622, adult ♂, 662 mm TL, Norfolk Island, Australia ; MNHN-IC-1997-3624, adult ♂, 650 mm TL, Norfolk Island, Australia ; MNHN-IC-1997-3625, adult ♂, 645 mm TL, Norfolk Island, Australia ; MNHN-IC-1997-3626, adult ♀, 650 mm TL, Norfolk Island, Australia ; MNHN-IC-1997-3627, adult ♀, 690 mmTL, Norfolk Island, Australia ; MNHN-IC-1997-3628, adult ♀, 695 mm TL, Norfolk Island, Australia ; MNHN-IC-2002-1196, adult ♂, 655 mm TL, New Caledonia ; MNHN-IC-2002-1197, adult ♂, 680 mm TL, New Caledonia ; MNHN-IC-2002-1392, adult ♀, 665 mm TL, New Caledonia, 23°1’1”S, 166°55’1”E .

GEOGRAPHICAL DISTRIBUTION. — It occurs in the Southwestern Pacific Ocean, surrounding waters from New Caledonia, Vanuatu, and Norfolk Island ( Australia) ( Fig. 15 ).

DIAGNOSIS. — Squalus melanurus is distinguished from all its congeners by: body conspicuously slender; conspicuous black caudal-fin lower lobe; snout obtuse and markedly elongate, its preorbital length 9.6% (10.0-10.9%) TL; more elongate distance from nostrils to tip of snout, comprising 6.9% (7.2-8.4%) TL; larger preoral length, corresponding to 12.6% (12.7-14.3%) TL; more elongate distance from spiracle to tip of snout, its length 14.7% (15.3-16.8%) TL. It is further distinct from its congeners by having broader internarial space, its width 5.1% (5.1-6.1%) TL, and more elongate second dorsal-fin spine, its length 6.2% (4.9-6.5%) TL. Squalus melanurus also differs from congeners by monospondylous vertebrae 41-41 (vs 49 for S. bucephalus vs 45-46 for S. mitsukurii vs 43-46 for S. chloroculus vs 45-47 for S. griffini vs 36-39 for S. nasutus ), precaudal 85-94 (vs 78-83 for S. nasutus ), and total vertebrae 114-120 (vs 124 for S. bucephalus vs 103-109 for S. nasutus ).

DESCRIPTION

General body, snout and eyes ( Figs 1 , 2 )

Body fusiform and markedly thin throughout all its extension; body with its greatest width at head, its width 1.3 (1.0- 1.3) times trunk width and 1.8 (1.1-1.4) times abdomen width. Head flattened dorsally and conspicuously tapered, its height 0.8 (0.8-1.0) times trunk and abdomen height; head elongate, its length 23.6% (22.4-26.8%) TL. Snout obtuse at the tip and conspicuously extended, its preorbital length 9.6% (10.0-10.9%) TL; anterior margin of nostrils bi-lobed with second lobe pointed, larger and thinner than first lobe; nostrils much closer to mouth than tip of snout, its prenarial length 1.4 (1.4-1.7) times distance from nostril to upper labial furrow and 0.5 (0.6-0.6) times preoral length; internarial width 1.2 (1.1-1.3) times larger than length of eye. Eyes narrowly oval with anterior margin pointed; posterior margin of eye pointed to somewhat notched; eyes large, its length 2.7 (2.3-3.1) times greater than its height. Prespiracular length 0.6 (0.6-0.7) times prepectoral length and 1.5 (1.5-1.6) times preorbital length. Spiracles crescent and markedly constricted, its length 0.2 (0.2-0.3) times eye length, placed laterally behind the eyes. Prebranchial length 1.4 (1.3-1.4) times prespiracular length. Gill slits straight to slightly concave, very low with fifth gill slit 1.2 (1.0-1.6) times greater in height than first gill slit.

Mouth and dentition ( Figs 2 , 6 )

Preoral length comprising 2.0 (1.9-2.3) times greater than mouth width. Mouth somewhat arched and very narrow, its width 0.9 (0.8-0.9) times prenarial length and 1.3 (1.1-1.3) times larger than internarial space; upper labial furrow short with slender fold, its length 2.1% (1.9-2.6%) TL; lower labial furrow also short, not reaching head laterally and lacking a fold. Teeth unicuspid and similar in both jaws; upper teeth smaller than lower teeth; mesial cutting edge convex; mesial heel notched on upper teeth and weakly notched on lower teeth; distal heel rounded; cusp short and thick, pointed obliquely; apron very short and heavy, placed at midline of the crown base. Three series of functional teeth on upper jaw and two series on lower jaw in holotype. Upper teeth rows 13-1-13; lower teeth rows 11-1-11.

Dorsal fins ( Fig. 3 )

Pre-first dorsal length 1.4 (1.2-1.4) times prepectoral length; origin of first dorsal fin prior to vertical traced at pectoralfin free rear tips. First dorsal fin upright and slender at apex with anterior margin convex and posterior margin straight to weakly concave near free rear tips; first dorsal-fin apex very narrow and rounded; first dorsal-fin free rear tip pointed; first dorsal-fin inner margin short, its length 5.8% (5.0-5.8%) TL; first dorsal fin elongate, its length 13.8% (12.9-14.1%) TL, and tall with its height 1.6 (1.5-1.8) times greater than length of first dorsal-fin inner margin. First dorsal fin length 1.0 (1.0-1.2) times length of second dorsal fin. First dorsal-fin spine short, its length 0.4 (0.3- 05) times height of first dorsal fin, and slender with base width 0.8% (0.7-1.0%) TL. Interdorsal space 1.0 (0.9-1.1) times prepectoral length, and 2.4 (2.3-3.0) times dorsalcaudal space. Pre-second dorsal length 2.7 (2.4-2.8) times prepectoral length. Second dorsal fin upright and conspicuously slender; second dorsal-fin apex rounded and lobe-like; second dorsal-fin anterior margin convex and posterior margin concave; second dorsal-fin free rear tip pointed; second dorsal-fin inner margin very short, its length 4.7% (4.1-4.8%) TL; second dorsal fin tall, its height 1.5 (1.3- 1.9) times length of second dorsal-fin inner margin. Second dorsal spine very thin, its base width 0.7% (0.7-0.9%) TL, and elongate, its length 0.9 (0.7-0.9) times height of second dorsal fin, almost reaching second dorsal fin apex; second dorsal-fin spine length 1.6 (1.1-2.0) times more elongate than length of first dorsal-fin spine.

Paired fins and claspers ( Figs 4 , 7 )

Pectoral fins somewhat narrow with pectoral-fin posterior margin length 11.1% (9.3-12.0%) TL; pectoral-fin anterior margin straight, although convex distally; pectoral-fin inner margin convex; pectoral-fin posterior margin straight to weakly concave; pectoral-fin apex rounded and lobe-like; pectoral-fin free rear tips rounded; pectoral-fin anterior margin elongate, its length 1.7 (1.7-2.0) times larger than length of pectoralfin inner margin, and 1.3 (1.2-1.5) times greater in length than pectoral-fin posterior margin. Pectoral-pelvic space 0.6 (0.5-0.9) times pelvic-caudal distance. Pelvic fins small, its length 12.7% (10.4-12.2%) TL; pelvic-fin margins convex; pelvic-fin free rear tips rounded and lobe-like; origin of pelvic fins placed at midline between first and second dorsal fins, slightly nearest to first dorsal fin. Claspers rather thick and short, its inner length 1.1 (1.1-1.3) times more elongate than length of pelvic-fin inner margin; clasper groove longitudinal, dorsal and small; apopyle and hypopyle constricted, placed anterior and posteriorly in the clasper groove, respectively; rhipidion flap-like, short, and conspicuously thin, located medial-distally at the clasper.

Caudal fin ( Fig. 5 )

Caudal keel prominent, located laterally in the caudal peduncle from vertical traced at insertion of second dorsal fin to behind origin of caudal fin. Caudal fin small, its dorsal caudal margin length 0.9 (0.7-0.9) times head length, and 2.2 (1.8-4.2) times larger than length of preventral caudal margin; dorsal caudal margin straight; upper postventral caudal margin somewhat convex to straight; lower postventral caudal margin straight; preventral caudal margin convex; dorsal caudal tip pointed; ventral caudal tip pointed to weakly rounded; caudal fin very thin on upper and lower lobes, its width at caudal fork 6.3% (5.7-6.7%) TL.

Dermal denticles

Tricuspid and imbricate dermal denticles, very broad at crown with its length slightly greater than its width; cusps pointed and posterior; lateral cusps smaller than median cusp, although almost reaching its tip; median ridge elongate and thick, turning thin distally; lateral ridges thin and as large as median ridge; anterior margin of the crown arrow-shaped with anterior furrow oval and shallow; small lateral ridges aside anterior furrow may be present in some denticles ( Fig. 8 ).

Coloration

Body greyish brown dorsally and whitish grey ventrally ( Fig. 1 ); both dorsal fins grey, light grey at fin base, and narrowly dark grey at the apex; dorsal-fin free rear tips slightly white. Dorsal-fin spines light brown, dark brown anteriorly and white at tips ( Fig. 3 ). Pectoral fins dark grey with pectoral-fin posterior margin somewhat whitish, although not uniform; pectoral fins light grey ventrally and white at its base ( Fig. 4 ). Pelvic fins dark grey dorsally and whitish grey ventrally; pelvic-fin posterior margins slightly white. Caudal fin mostly grey, light grey over vertebral column; dorsal caudal margin with black upper caudal fringe small, placed distally, although not reaching dorsal caudal tip; upper postventral caudal margin broadly white till caudal fork; lower postventral caudal margin black; lower caudal lobe conspicuously black with white basal marking at origin of preventral caudal margin; black caudal stripe absent ( Fig. 5 ).

Vertebral counts

41 (41-41) monospondylous vertebrae; 85 (90-94) precaudal vertebrae; 29 (26-28) caudal vertebrae; 114 (118-120) total vertebrae.

REMARKS

Squalus melanurus is known to occur on upper insular slopes at depth range between 34-480 m ( Fourmanoir 1979; Four- manoir & Rivaton 1979; Kulbichi et al. 1990; Compagno et al. 2005; Fricke et al. 2011). It is also observed in shallow waters in Chesterfield Islands (at 34 m), and at medium to deeper waters (between 223-790 m) in New Caledonia and Vanuatu. Biology of this species is poorly known with little information about its reproduction and feeding habits available in the literature (e.g. Fourmanoir & Rivaton 1979; Fowler & Séret 2003). Studies on life-history traits such as maturation and offspring size associated to population dynamics on growth and density are of urgent concern for conservation purposes of Squalus melanurus . Paratypes of S. melanurus are apparently lost even though 17 specimens, measuring between 620-750 mm TL, were mentioned in Fourmanoir & Rivaton (1979).

Figures

FIG. 1. — Squalus melanurus Fourmanoir,1979 in lateral view:A, MNHN-IC-1980-0460 (holotype of S. melanurus), adult male,670 mm TL;B, MNHN-IC-1978-0693 (holotype of S. rancureli Fourmanoir, 1979), adult male,680 mm TL;C, MNHN-IC-2002-1392, adult female,665 mm TL; D, MNHN-IC-1997-3619, juvenile female, 527 mm TL. Scale bars: 50 mm.

FIG. 2. — Head in ventral view of Squalus melanurus Fourmanoir, 1979. A, MNHN-IC-1997-3619, juvenile female, 527 mm TL. B, MNHN-IC-1980-0460 (holotype of S. melanurus), adult male, 670 mm TL; C, MNHN-IC-1978-0693 (holotype of S. rancureli Fourmanoir, 1979), adult male, 680 mm TL. Scale bars: 50 mm.

FIG. 3. — First and second dorsal fins of Squalus melanurus Fourmanoir,1979:A, B, MNHN-IC-1997-3619, juvenile female,527 mm TL;C, D, MNHN-IC-2002-1196, adult male, 655 mm TL; E, F, MNHN-IC-1978-0693 (holotype of S. rancureli Fourmanoir, 1979), adult male, 680 mm TL. Scale bars: 20 mm.

FIG. 4. — Pectoral fins of Squalus melanurus Fourmanoir, 1979 in ventral view: A, MNHN-IC-1997-3619, juvenile female, 527 mm TL; B, MNHN-IC-2002-1196, adult male, 655 mm TL; C, MNHN-IC-1978-0693 (holotype of S. rancureli Fourmanoir, 1979), adult male, 680 mm TL. Scale bars: 20 mm.

FIG. 5. — A, B, Caudal fin of Squalus melanurus Fourmanoir, 1979, showing black lower caudal lobe: A, MNHN-IC-1997-3619, juvenile female, 527 mm TL; B, MNHN-IC-2002-1197, adult male, 655 mm TL; C, caudal fin of holotype of S. rancureli Fourmanoir, 1979 (MNHN-IC-1978-0693). Scale bars: 20 mm.

FIG. 6. — Upper (A) and lower (B) teeth of Squalus melanurus Fourmanoir,1979 (MNHN-IC-1997-3626) in labial view. Scale bars: 1 mm.

FIG. 7. — External dorsal view of right clasper of holotype of Squalus melanurus Fourmanoir, 1979 (MNHN-IC-1980-0460, adult male, 670 mm TL). Abbreviations: cg: clasper groove; hp: hypopyle; P2: pelvic fin; rh: rhipidion. Scale bar: 20 mm.

FIG. 8. — Scanning electron microscopy of dermal denticles of Squalus melanurus Fourmanoir,1979,MNHN-IC-1997-3627, adult female,690 mm TL.Scale bars: A, 100 μm; B, 200 μm.

FIG. 15. — Map of distribution of Squalus melanurus Fourmanoir, 1979 (●) and S. bucephalus Last, Séret & Pogonoski, 2007 (●) in the Coral Sea. A: holotype of S. melanurus.