Squalus bucephalus Last, Séret & Pogonoski, 2007

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 : 168-171

Squalus bucephalus Last, Séret & Pogonoski, 2007

Bighead spurdog; Aiguillat à grosse tête

( Figs 9-15 ; Tables 2-3 )

Squalus bucephalus Last, Séret & Pogonoski, 2007: 23-29 (original description; illustrated. Type by original designation. Type locality Norfolk Ridge, south of New Caledonia, 405-411 m depth). — Ebert et al. 2013: 78, 86 (cited, description; Southwest Pacific Ocean). — Weigmann 2016: 903 (listed; Southwestern Pacific Ocean). — Bernot & Boxshall 2017: 275-276, 288 (cited, listed; New Caledonia).

Squalus sp. – Séret 1994: 7 (listed; New Caledonia).

MATERIAL EXAMINED. — MNHN-IC-1997-3634, juvenile ♂, 520 mm TL, Norfolk Ridge, New Caledonia, 24°43’1”S, 168°6’0”E, 500-600 m depth ; MNHN-IC-1997-3635, juvenile ♀, 476 mm TL, Norfolk Ridge, New Caledonia, 24°43’1”S, 168°6’0”E, 500- 600 m depth ; MNHN-IC-1997-3636, juvenile ♀, 495 mm TL, Norfolk Ridge, New Caledonia, 24°43’1”S, 168°6’0”E, 500-600 m depth ; MNHN-IC-1997-3641 (paratype of S. bucephalus ), juvenile ♀, 430 mm TL, Norfolk Ridge, New Caledonia, 23°39’0”S, 167°43’59”E, 420-470 m depth ; MNHN-IC-1997-3657, adult ♂, 705 mm TL, New Caledonia, 23°43’1”S, 168°15’0”E, 405-411 m depth ; MNHN-IC-1997-3659, adult ♂, 805 mm TL, Stylaster Seamount, Norfolk Ridge, New Caledonia, 23°37’1”S, 167°39’0”E, 486-962 m depth ; MNHN-IC-1997-3662, adult ♂, 795 mm TL, Stylaster Seamount, Norfolk Ridge, New Caledonia, 23°36’0”S, 167°40’59”E, 448-880 m depth ; MNHN-IC-1998-1017, adult ♂, 810 mm TL, New Caledonia, 23°43’1”S, 168°15’0”E, 405-411 m depth ; MNHN-IC-2006-1754 (holotype of S. bucephalus ), juvenile ♂, 550 mm TL, Norfolk Ridge, south of New Caledonia, 23°43’S, 168°16’E, 405-411 m depth, collected on 28.XI.1993 ; NMNZ P 34030 (paratypes of S. bucephalus ), two adult ♂, 787-802 mm TL, Stylaster Seamount, Norfolk Ridge, New Caledonia, 23°35’S, 167°42’E, 448-880 m depth .

GEOGRAPHICAL DISTRIBUTION. — Squalus bucephalus is endemic to New Caledonia in the Southwestern Pacific Ocean ( Fig. 15 ).

DIAGNOSIS. — Short-snouted dogfish shark from New Caledonia that it is distinguished from its congeners by: head conspicuously humped dorsal-posteriorly and wide, its width at mouth 13.5% (12.1-13.9%) TL; anterior margin of nostrils conspicuously bilobate and broad; mouth straight and wide, its width 8.7% (7.6-8.8%) TL; caudal fin very slender on upper and lower lobes; caudal fin elongate, its dorsal caudal margin length 24.2% (21.7-23.9%); smaller pelvic-caudal space 24.9% (23.1-

26.3%) TL. It is clearly separated from S. melanurus by snout conspicuously short, its prenarial length 1.0-1.1 times distance nostril-upper labial furrow (vs snout conspicuously elongate, its prenarial length 1.4-1.7 times distance nostril-upper labial furrow in S. melanurus ), prespiracular length (12.2-14.0% TL for S. bucephalus vs 14.7-16.8% TL for S. melanurus ), and preoral length (9.2-10.9% TL for S. bucephalus vs 12.6-14.3% TL for S. melanurus ). It is further distinct from this species by having lower caudal lobe conspicuously white (vs conspicuously black), and dermal denticles unicuspidate and lanceolate (vs tricuspidate and rhomboid). Squalus bucephalus is also separated from S. melanurus by number of monospondylous (49 vs 41 for S. melanurus ), caudal (31 vs 26-29 for S. melanurus ), and total vertebrae (124 vs 114-120 for S. melanurus ).

REMARKS

Squalus bucephalus is a deep-water dogfish shark that occurs in the continental slope between 405-962 m depth, although it is often caught at depths between 405-600 meters. It is a species with very restrict geographical distribution and whose biology is totally unknown. Females are rarely caught in New Caledonia, arousing attention for conservation and fisheries management. Studies on population size and trends, maturation, feeding and reproduction are imperative for threatened assessments of this species.

Figures

FIG. 9. — Squalus bucephalus Last, Séret & Pogonoski, 2007 in lateral view: A, MNHN-IC-1998-1017, adult male, 810 mm TL; B, MNHN-IC-1997-3636, juvenile female, 495 mm TL. Scale bars: 50 mm.

FIG. 10. — Detail of head in anterior dorsal view (A) and right nostrils (B) of holotype of Squalus bucephalus Last, Séret & Pogonoski,2007 (MNHN-IC-2006-1754, juvenile male, 550 mm TL). Scale bar: A, 20 mm; B, not to scale.

FIG. 11. — First (A, C) and second (B, D) dorsal fins of Squalus bucephalus Last, Séret & Pogonoski, 2007: A, B, MNHN-IC-1998-1017, adult male, 810 mm TL; C, D, MNHN-IC-1997-3636, juvenile female, 495 mm TL. Scale bars: 20 mm.

FIG. 12. — Pectoral fin in ventral view (A) and right clasper in dorsal view (B) of Squalus bucephalus Last, Séret & Pogonoski, 2007: A, MNHN-IC-1998-1017, adult male, 810 mm TL; B, NMNZ P 34030 (paratype), adult male, 787 mm TL. Abbreviations: ap, apopyle; cg, clasper groove; hp, hypopyle; P2, pelvic fin; rh, rhipidion. Scale bar: 20 mm.

FIG. 13. — Upper (A) and lower (B) teeth of Squalus bucephalus Last, Séret & Pogonoski,2007 (MNHN-IC-1997-3662, adult male,795 mm TL) in labial view. Scale bars: 1 mm.

FIG. 14. — Caudal fin of paratype of Squalus bucephalus Last,Séret & Pogonoski, 2007 (NMNZ P 34030, adult male, 787 mm TL). Scale bar: 20 mm.

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.