Sibogasyrinx sangeri Kantor, Fedosov & Puillandre, 2018

Kantor, Yuri I. & Puillandre, Nicolas, 2021, Rare, deep-water and similar: revision of Sibogasyrinx (Conoidea: Cochlespiridae), European Journal of Taxonomy 773, pp. 19-60 : 38-40

Sibogasyrinx sangeri Kantor, Fedosov & Puillandre, 2018 (= PSH 7)

Figs 7 , 8A–B

Sibogasyrinx sangeri Kantor, Fedosov & Puillandre, 2018: 58 , figs 5e–n, 6c–d.

Material examined

Holotype PAPUA NEW GUINEA • 07°52′ S, 148°03′ E; depth 575–655 m; BIOPAPUA, stn CP3729; MNHN- IM-2009-17022 (sequenced).

Other material (all sequenced)

PAPUA NEW GUINEA • 2 lv; 04°04′ S, 151°56′ E; depth 585–601 m; BIOPAPUA, stn CP3671; MNHN-IM-2009-16989 , MNHN-IM-2013-52052 • 1 lv; 04°24′ S, 151°50′ E; depth 788–805 m; BIOPAPUA, stn CP3674; MNHN-IM-2009-16995 • 1 lv; off Woodlark Is. ; 09°08′ S, 152°19′ E; depth 448–470 m; BIOPAPUA, stn CP3742; MNHN-IM-2009-17057 • 1 lv; 05°39′ S, 153°59′ E; depth 654– 660 m; BIOPAPUA, stn CP3750; MNHN-IM-2009-17021 • 1 lv; N of Long I.; 05°10′ S, 147°03′ E; depth 724 m; PAPUA NIUGINI, stn CP3982; MNHN-IM-2013-19752 • 1 lv; Dampier Strait , E of Umboi I.; 05°35′ S, 148°13′ E; depth 630–870 m; PAPUA NIUGINI, stn CP4014; MNHN-IM-2013-19961 .

PHILIPPINES • 1 lv; 15°45′ N, 121°45′ E; depth 562 m; AURORA 2007, stn CP2663; MNHN- IM-2009-13434 .

SOLOMON ISLANDS • 1 lv; Sta Isabel I.; 08°47′ S, 159°40′ E; depth 645–840 m; SALOMON 2, stn CP2181; MNHN-IM-2009-16766 • 2 lv; Rendova I. ; 08°36′ S, 157°27′ E; depth 509–520 m; SALOMON 2, stn CP2288; MNHN-IM-2007-42523 , MNHN-IM-2009-16779 .

Description

MEASUREMENTS. Holotype: SL 54.1 mm, AL (with canal) 31.3 mm, AL (without canal) 16.4 mm, SW 14.1 mm. Largest available specimen attains SL 55.8 mm (MNHN-IM-2009-16779; Fig. 7D–E ).

SHELL. Thin, fragile, variable in shape, from narrowly fusiform to moderately broad (SW/SL ratio from 0.22 to 0.27), with rather high spire and long, narrow, straight siphonal canal. Protoconch small, globose, of 1.75 strongly convex, microshagreened whorls. Protoconch/teleoconch transition indistinct. Protoconch diameter about 1.1 mm, height 1.2 mm. Early teleoconch whorls angular, usually in lower part just above suture, but sometimes at mid-whorl; last whorl strongly to very weakly angled or evenly rounded, even in specimens of the same size. Teleoconch comprising up to 10 whorls. Suture shallow, subsutural ramp with a row of distinct, closely spaced nodules, 10 on first whorl, 14 on second whorl, becoming more broadly spaced and less discernible on later whorls, sometimes obsolete on last whorl of largest specimens. Subsutural zone very weakly concave, nearly straight on penultimate and last whorls, smooth except for a few irregularly spaced and indistinct spiral threads (sometimes oblique), or several rather pronounced flattened spiral cords ( Fig. 7J ; MNHN-IM-2009-13434). Lower part of whorls with a row of larger, more pronounced nodules, just above suture in upper whorls or sometimes nearer midwhorl. In some specimens nodules absent on last whorl. Last whorl may bear low carina at periphery (in specimens with nodules absent), giving it very weakly angled outline. Below periphery 2–3 distinct spiral cords on penultimate whorl and about 30 cords below carina on last whorl and 20 on canal. Shell base gradually narrowing towards long, nearly straight siphonal canal. Aperture narrow, constricted posteriorly with broad, very thin parietal callus, outer lip partially broken, convex and weakly angled in upper part and slightly convex below shoulder, and shallowly concave at transition to canal. Anal sinus moderately deep, subsutural, broadly arcuate, growth lines confluent with large forward extension of outer lip. Growth lines thin but distinct. Shell uniformly off-white, protoconch light tan.

ANATOMY (n = 1, MNHN-IM-2009-16995). Proboscis of moderate length in contracted stage, buccal mass situated outside proboscis. Oesophagus very broad, forming short loop before passing through nerve ring. Venom gland opening into oesophagus ventrally and immediately posterior to nerve ring.

RADULA (n = 1, MNHN-IM-2009-16995) ( Fig. 8A–B ). Relatively short, comprising ca 40 rows of teeth, with long nascent part (15–16 rows). Radula length 2.2 mm (16% of AL without canal), width up to 365 μm (2.7% of AL without canal). Central tooth with subrectangular basal plate, very shallowly arcuate anteriorly, with distinct borders and weak cusp. Marginal teeth flat when formed, becoming trough-shaped during maturation, folded longitudinally when fully formed. On developing part of radula, folding of teeth occurs abruptly, within one subsequent row (on Fig. 8B white arrow indicates last still unfolded tooth, while black arrow with white outline indicate the first folded tooth). Folding evident at 17 th row in radula studied. Resulting folded tooth moderately broad, with sharp pointed tip, formed by overlapping of both thickened margins (on Fig. 8A these overlapping parts are marked by hollow white arrows).

Distribution

This species is known from the Solomon Islands, Papua New Guinea and the Philippines, over a relatively broad bathymetric range, from 448 to 788 m.

Figures

Fig. 7. Sibogasyrinx sangeri Kantor, Fedosov & Puillandre, 2018. A–B. Holotype, Papua New Guinea, MNHN-IM-2009-17022, SL 54.1 mm. C. Papua New Guinea, MNHN-IM-2009-16995, SL 47.7 mm (radula seen on Fig. 8A–B). D–E. Solomon Islands, MNHN-IM-2009-16779, SL 55.8 mm. F. Papua New Guinea, MNHN-IM-2009-17021, SL 53.7 mm.G–H. Papua New Guinea, MNHN-IM-2009-17057, SL 38.8 mm. I–J. Philippines, MNHN-IM-2009-13434, SL 36.9 mm. K. Solomon Islands, MNHN- IM-2009-16766, SL 26.3 mm. All shells to the same scale.

Fig. 8. Radulae of species of Sibogasyrinx Powell, 1969. A–B. Sibogasyrinx sangeri Kantor, Fedosov & Puillandre, 2018, MNHN-IM-2009-16995 (shell seen on Fig. 7C). A. Part of radula with fully formed marginal teeth; white hollow arrow indicates overlapping edges of the tooth at its tip. B. Part of radula showing transition between unfolded (white arrow) and completely longitudinally folded (black arrow) marginal teeth (ae = anterior tooth edge; pe = posterior tooth edge). C. Sibogasyrinx filosa Ardovini, 2021, Solomon Islands, MNHN-IM-2009-16831 (shell seen Fig. 9E–F). D. Sibogasyrinx lolae sp. nov., MNHN-IM-2009-29311. E. Sibogasyrinx maximei sp. nov., holotype, MNHN-IM-2013-45883, anterior end of radula. F. Sibogasyrinx pagodiformis sp. nov., MNHN-IM-2009-11327.