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 : 30-32

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

Figs 3A–G , 4A–B

Material examined (all sequenced)

PHILIPPINES • 1 lv; 15°20′ N, 121°37′ E; depth 593–600 m; AURORA 2007, stn CP2729; MNHN- IM-2009-13451 .

SOUTH CHINA SEA • 2 lv; 20°01′ N, 115°02′ E; depth 700–723 m; NanHai 2014, stn CP4118; MNHN- IM-2013-44574 , MNHN-IM-2013-44605 • 1 lv; 20°29′ N, 116°08′ E; depth 590–633 m; DongSha 2014, stn CP4129; MNHN-IM-2013-50215 .

Description

MEASUREMENTS (largest specimen). SL 65.2 mm, AL (with canal) 35.1 mm, AL (without canal) 21.0 mm, SW 18.5 mm.

SHELL. Moderately thick, strong except for fragile outer aperture lip, fusiform, with high spire and long, narrow, straight siphonal canal. Protoconch small, globose, of about 1.5 strongly convex, microshagreened whorls, eroded or missing in all specimens. Early teleoconch whorls weakly to moderately angular at shoulder. Largest available specimen (SL 65.2 mm) of 10.3 teleoconch whorls. Suture shallowly impressed, subsutural ramp broad, weakly concave to flat. All teleoconch whorls with a subsutural row of nodules, corresponding in shape to upper parts of thickened growth lines. Nodules more distinct on upper whorls, increasing in number, up to 30 on penultimate whorl and 37 on last whorl in largest specimen. Subsutural ramp may be completely smooth, or sometimes with very weak spiral striation or dendritic lines. Shoulder with pronounced thickened and rounded nodules, reaching lower suture, weakly opisthocline on upper whorls and more strongly inclined and confluent with growth lines on lower whorls. Nodules evanesce on last and even penultimate whorls at SL over 50 mm and shoulder becomes evenly rounded; their number increase with size from 14–15 on upper whorls to 21–22 on lower whorls. Spiral sculpture of 3–6 moderately pronounced, closely spaced narrow cords on shoulder, crossing shoulder nodules on spire whorls. Last whorl below shoulder with 40–45 cords varying in width, their intervals 0.5–2 times width of cords, also distinct on canal. Shell base gradually narrowing towards long, narrow, nearly straight siphonal canal. Aperture narrow, constricted posteriorly, with narrow and thin parietal callus, outer lip with rounded angle at shoulder, weakly convex below shoulder and weakly concave at transition to canal. Anal sinus moderately deep, subsutural, broadly arcuate, confluent with large forward extension of outer lip. Shell off-white with very light yellowish subsutural band, protoconch pale tan. Periostracum persists on part of shell, light yellowish.

ANATOMY. Foregut similar to that of Sibogasyrinx cf. pyramidalis 2 (see below), except for presence of a large oval accessory salivary gland, adjoining oesophagus, with rather thick duct, entering proboscis and following along its wall.

RADULA (n = 2; MNHN-IM-2009-13451, MNHN-IM-2013-50215). Comprising approximately 40 rows of teeth, 15 nascent, short, length ca 2.5 mm (15% of AL without canal). Radula width up to 530 μm (3.3% of AL without canal). Central tooth with broad, subrectangular basal plate and anteriorly broadly concave, borders distinct and with narrow but rather long, sharply pointed cusp. Marginal teeth with strongly thickened posterior edges, folded longitudinally. When immature, teeth nearly flat with elevated posterior edge, on developing part of radular tooth folding clearly visible (on Fig. 4A not fully folded teeth are marked by white arrows), bringing posterior and anterior edges close together. During tooth maturation the edges, particularly posterior one, progressively thicken, so that fully formed tooth appears duplex ( Fig. 4B ).

Distribution

The confirmed distribution is the South China Sea and the Philippines Sea, at 590– 700 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).