Sibogasyrinx cf. pyramidalis ( Schepman, 1913 )

Kantor, Yuri I. & Puillandre, Nicolas, 2021, Rare, deep-water and similar: revision of Sibogasyrinx (Conoidea: Cochlespiridae), European Journal of Taxonomy 773, pp. 19-60 : 32-35

Sibogasyrinx cf. pyramidalis ( Schepman, 1913) 2 (= PSH 1)

Figs 3J–Q , 4C–D , 5

Material examined (all sequenced)

PAPUA NEW GUINEA • 2 lv; off Manus I.; 02°16′ S, 147°29′ E; depth 679–685 m; BIOPAPUA, stn CP3689; MNHN-IM-2009-16972 , MNHN-IM-2009-16973 • 1 lv; N of Rabaul; 04°04′ S, 151°56′ E; depth 585–601 m; BIOPAPUA, stn CP3671; MNHN-IM-2009-16988 • 1 lv; N of Rabaul; 04°04′ S, 151°50′ E; depth 702–724 m; BIOPAPUA, stn CP3672; MNHN-IM-2009-17000 • 1 lv; Bismarck Sea , N of Long I.; 05°11′ S, 147°03′ E; depth 688 m; PAPUA NIUGINI, stn CP3981; MNHN-IM-2013-19716 • 1 lv; Bismarck Sea , N of Long I.; 05°10′ S, 147°03′ E; depth 724 m; PAPUA NIUGINI, stn CP3982; MNHN-IM-2013-19745 • 1 lv; Bismarck Sea , NW of Long I.; 05°12′ S, 146°59′ E; depth 470–508 m; PAPUA NIUGINI, stn DW3983; MNHN-IM-2013-19768 • 1 lv; New Ireland, 02°42′ S, 150°02′ E; depth 827–966 m; KAVIENG 2014, stn CP4483; MNHN-IM-2013-58845 .

Description

MEASUREMENTS (largest specimen). SL 65.2 mm, AL (with canal) 34.7 mm, AL without canal 22.9 mm, SW 18.0 mm.

SHELL. Extremely similar to that of Sibogasyrinx cf. pyramidalis 1. The only slight difference is the larger number of spiral cords crossing the shoulder nodules. Penultimate whorl of S. cf. pyramidalis 1 with 5–6 cords (increasing with SL), 6–8 in S. cf. pyramidalis 2.

ANATOMY (n = 2, MNHN-IM-2009-16972, MNHN-IM-2009-17000). Head with long, cylindrical tentacles, rounded on tips with closely spaced bases, eyes absent.One specimen(MNHN-IM-2009-17000) male, with long penis with obliquely truncated tip. Seminal papilla occupies entire tip and is surrounded by circular fold. Proboscis long, coiled, with broad conical base, occupied by large bulbous buccal mass, spanning posterior ¼ of proboscis and protruding backwards from proboscis. Proboscis sheath with very thin transparent walls. Remaining anterior part of proboscis narrow, gradually diminishing in diameter towards its tip. Proboscis retractors well defined, powerful and numerous, attached to posteriormost edge of rhynchodeum. Radular sac and short oval odontophore situated on right side of buccal mass, posterior to rear of proboscis. Oesophagus adjoining buccal mass slightly constricted and forming a moderately long loop before passing through nerve ring. Salivary glands irregularly shaped, covering dorsal portion of nerve ring. Accessory salivary gland not traced. Venom gland thick, long, strongly convoluted, opens dorsally into oesophagus, immediately posterior to nerve ring ( Fig. 5B ). Muscular bulb oval, of moderate size, situated to the right of oesophagus.

RADULA (n = 2; MNHN-IM-2009-16972, MNHN-IM-2009-17000). Comprising approximately 40 rows of teeth, 15 nascent, short, length (measured only in MNHN-IM-2009-16972) ca 1.7 mm (14% of AL without canal). Radula width up to 300 μm (2.5% of AL without canal). Shape of teeth very similar to that of Sibogasyrinx cf. pyramidalis 1, central tooth has less rounded posterior margin and in one specimen (MNHN-IM-2009-17000, Fig. 4D ) the cusp is obtuse.

Remarks

Despite the similarities in shell and radular morphology, Sibogasyrinx cf. pyramidalis 1 and Sibogasyrinx cf. pyramidalis 2 are clearly distinct from a molecular perspective. One morphological character of the foregut that separates the two species is the presence of an accessory salivary gland in the former.

Distribution

The confirmed distribution is Papua New Guinea, at 585– 827 m.

Figures

Fig. 3. Sibogasyrinx pyramidalis (Schepman, 1913) complex. A–G. Sibogasyrinx cf. pyramidalis 1. A–C. South China Sea, MNHN-IM-2013-44605, SL 65.2 mm. D–F. Philippines, MNHN- IM-2009-13451, SL 46.8 mm. G. South China Sea, MNHN-IM-2013-44574, SL 53.9 mm. H–I. Surcula pyramidalis Schepman, 1913, holotype, ZMA.MOLL.136836, SL 45 mm (photos by K. Hasegawa, copyright Naturalis, Leiden). J–Q. Sibogasyrinx cf. pyramidalis 2, Papua New Guinea. J–L. MNHN- IM-2013-19745, SL 65.2 mm.M–O. MNHN-IM-2009-17000, SL 59.2 mm. P. MNHN-IM-2009-16973, SL 41 mm. Q. MNHN-IM-2009-16988, SL 43 mm. R–T. Sibogasyrinx archibenthalis (Powell, 1969), holotype, USNM 238773, SL 41.8 mm. All shells to same scale.

Fig. 4. Radulae of species of Sibogasyrinx Powell, 1969. A–B. S. cf. pyramidalis (Schepman, 1913) 1, MNHN-IM-2009-13451 (shell seen on Fig. 3D–F). A. Part of radula with marginal teeth not fully formed; white arrows indicate teeth that are not fully folded longitudinally (ae = anterior tooth edge; pe = posterior tooth edge). B. Part of radula with fully formed marginal teeth. C. S. cf. pyramidalis 2, MNHN-IM-2009-16972. D. S. cf. pyramidalis 2, MNHN-IM-2009-17000 (shell seen on Fig. 3M–O). E. S. subula sp. nov., MNHN-IM-2007-17703. F. S. subula sp. nov., MNHN-IM-2009-13568 (shell seen on Fig. 6H–I).

Fig. 5. Anterior foregut of Sibogasyrinx cf. pyramidalis (Schepman, 1913) 2, MNHN-IM-2009-16972. A. Right latero-dorsal view. B. Dorsal view of the nerve ring and opening of the venom gland. Abbreviations: mb = muscular bulb of the venom gland; nr = circumoesophageal nerve ring; od = odontophore; oe = oesophagus; pr = proboscis; prr = proboscis retractors; rs = radular sac; sd = salivary duct; sg = salivary gland; vg = venom gland.