Clavus boucheti, Kilburn, Richard N., Fedosov, Alexander & Kantor, Yuri, 2014

Kilburn, Richard N., Fedosov, Alexander & Kantor, Yuri, 2014, The shallow-water New Caledonia Drilliidae of genus Clavus Montfort, 1810 (Mollusca: Gastropoda: Conoidea), Zootaxa 3818 (1), pp. 1-69 : 14-16

Clavus boucheti new species

( Figs. 2 G, H, 5 A–F)

Type material. Holotype: New Caledonia, LAGON, Grand récif Sud, Stn. 548, 22°56’S, 166°55’E, 32 m, MNHN IM–2000–26915. Paratypes: LAGON, Stn. 296, 22°41’S, 166°44’E, 26 m (1 specimen—MNHN IM–2000–26916), Stn. 339, 22°46’S, 166°48’E, 26 m (1 specimen—MNHN IM–2000–26917), Stn. 551, 23°00’S, 166°59’E, 9 m (1 specimen—MNHN IM–2000–26918).

Other material examined (total 17 lots, 22 spms, including type material):

New Caledonia, LAGON Stns. 290 (1 spm), 291 (1 spm), 297 (1 spm), 305 (2 spms), 546 (2 spms), 564 (1 spm), 305 (2 spms), 560 (1 spm), 572 (2 spms), 724 (1 spm), 762 (1 spm), 763 (1 spm), 771 (3 spms), 822 (1 spm).

Etymology. Named in honour of Philippe Bouchet, to whose energetic and innovative field programmes, his publications and the facilitation of research by specialists around the world, we owe most of our modern knowledge of the molluscan biodiversity of the New Caledonian region.

Distribution. Known only from New Caledonia, alive in 9– 67 m.

Diagnosis. Shell thick, broadly biconical, breadth/length 0.50–0.53, aperture/total length 0.41–0.49, suture shallow, not fissure-like, strongly undulating; fasciole massive, with shallow false umbilicus, fasciole surrounded by a wide, shallow spiral concavity; columella callus very thick, strongly concave, its base curved to right; outer lip slightly alate, stromboid notch very deep, anal sinus deeply U-shaped, directed slightly adapically, parietal pad relatively weak to absent. Initial four teleoconch whorls somewhat flattened, with axial ribs only indented at about 0.3 below suture; on later whorls ribs evanescing on upper half whorl, which is strongly concave (but rising high up preceding whorl); whorls strongly convex on their lower half where a series of prominent, rounded nodes, 9–11 per whorl; on last whorl these nodes evanesce at parietal level, but towards lip form rib-like extensions that reach fasciole level. Entire surface covered by very low, thin spiral ridge overall, more distant and slightly more angular on rostrum. White with a wide brown median band on last whorl, well-defined posteriorly, fading away gradually on base; columella and aperture white, brown band sometimes visible internally.

Description. Shell thick, broadly biconical, almost biturbinate (breadth/length 0.50–0.53) with relatively low, sharp, initially orthoconoid spire, aperture/total length 0.41–0.49); suture shallowly notched, not fissure-like, strongly undulating; fasciole massive, with shallow false umbilicus, circumscribed by a wide, shallow furrow, above which last whorl is more or less tumid; aperture wide, oblong-ovate, somewhat linear, columella callus very thick, strongly concave, its base curved to right, but not forming a terminal projection; siphonal canal wide, obliquely truncated, shallowly indented. Outer lip slightly alate, in side view weakly convex, serrated, stromboid notch very deep, anal sinus deeply U-shaped, directed slightly adapically, parietal pad relatively weak to absent.

First four whorls weakly convex; later whorls strongly concave below suture, lower half even more strongly convex, whorl periphery median on early whorls, submedian on later ones; subsutural region rising high up preceding whorl, slightly tumid. Axial ribs suture to suture on first four whorls, shallowly indented at about 0.3 below suture, thereafter evanescing in subsutural concavity and anteriorly forming a series of prominent, rounded nodes; on last whorl these evanesce at parietal level, except towards end of whorl, where they form rib-like extensions reaching fasciole level; in t/s ribs are broadly and roundedly angular, wider than intervals, 9–11 on each whorl, one nodule behind lip thickened into a varix. Entire surface covered by very low, thin spiral ridges, equal in width or narrower than their intervals, widely spaced and slightly more angular on rostrum. Collabral lines present, not forming threads.

White with a broad light to medium brown band around middle of last whorl, becoming darker behind outer lip, well defined posteriorly (where shows above suture towards end of penultimate whorl), fading away gradually on base; columella and aperture white, brown band sometimes showing through to interior.

Protoconch more or less worn in all specimens; bluntly conical, of ca two whorls, first depressed, diameter ca 830 Μm.

Measurements. 31.4 x 16.8 mm (holotype); 32.7 x 16.9 mm and 24.6 x 12.6 mm (largest and smallest paratype respectively).

Radula ( Fig. 2 G, H): Rachidian relatively broad, notched anteriorly, with strong median cusp and fine side denticles. Lateral teeth broad, arcuate, with 15 cusps, 2nd–4th from inner side being the longest and gradually diminishing in length towards outer side, where they evanesce. Marginal teeth rather long, with broader short blade, about 1/3 of teeth length. Blade edges thickened. Accessory limb weak. About 30 rows of teeth.

Remarks. This distinctively shaped species varies somewhat in adult size, breadth and in development of a parietal pad. Of New Caledonian species it is most similar to Clavus exasperatus , but it is distinguished by its large, rounded tubercles, the presence of spiral sculpture over the entire surface and a simple suture that is not recessed under the following whorl as in that species. Its large fasciole and prominent, rounded nodules distinguish it from most other Clavus species.

Figures

FIGURE 2. Radulae of Clavus canalicularis, C. exasperatus and C. boucheti. A – D. Clavus canalicularis A, B. EXPÉDITION MONTROUZIER, Koumac, Stn. 1277, SL 30.5 mm; C, D. LAGON, Nouméa Sector, Stn. 289, SL 22.8 mm (shell—Fig. 1 H); E, F. Clavus exasperatus, Loyalty Islands, Lifou, LIFOU 2000, Stn. 1420, SL 25.9 mm (shell—Fig. 4 H); G, H. Clavus boucheti, New Caledonia, LAGON, Grand Recif Sud, Stn. 305, SL 24.5 mm (shell—Fig. 5 F).