Clavus hylikos, 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 : 46-48

Clavus hylikos new species

( Figs. 23 A–D, 24 C, D)

Type material. Holotype: New Caledonia, EXPÉDITION MONTROUZIER, Touho Sector, Channel NE of Touho Bank, Stn. 1260, 20°44’S, 165°14’E, 49–59 m, MNHN IM–2000–26938; Paratypes: EXPÉDITION MONTROUZIER, Touho Stn. 1260, 20°44’S, 165°14’E, 49–59 m, (3— MNHN IM–2000–26939); Stn. 1261, 20°46’– 20°47’S, 165°15’– 165°16.5’E, 45–56 m (2— MNHN IM–2000–26940); Koumac Stn. 1309, 20°40.5’S, 164°13.4’E, 18 m (3— MNHN IM–2000–26941).

Other material examined (total 4 lots, 15 spms, including type material): New Caledonia, EXPÉDITION MONTROUZIER, Touho Stn. 1260 (5 spms).

Etymology. hylikos : of wood, Greek, for its colour, resembling walnut timber.

Distribution. New Caledonia (Touho and Koumac), dead shells only in ca 45– 59 m.

Diagnosis. Shell small (to ca 10 mm), variable in proportions (breadth/length 0.36–0.43, aperture/total 0.34–0.43), surface slightly glossy, base obliquely truncate, anal sinus roundly U-shaped, directed slightly adapically, parietal pad fairly large, not nodiform, stromboid notch rather deep. Axial ribs strong, from suture to rostrum, on later whorls shallowly notched anteriorly, forming a slight subsutural convexity (not a cord), 7–8 per whorl, sometimes continuous, sometimes not (causing a crenulate suture); terminal varix strong, slightly preceding outer lip, Microsculpture of growth lines and very faint, dense spiral striae. Rostrum with 4–8 declivous spiral ridges. Dark yellowish-brown, early part of spire paler, sometimes with a row of pale dots on ribs below indentation and 1–2 around base of last whorl, back of lip pale, varix with a pale yellowish blotch below suture.

Description. Shell small (to ca 10 mm), biconic-claviform (breadth/length 0.36–0.43), thick, with rather blunt apex and broad but linear aperture (aperture/total length 0.34–0.43), contracted near its base; siphonal canal moderately short and wide, with obliquely truncate base. Outer lip not distinctly alate, in side view gently convex, with rather deep stromboid notch, anal sinus roundly U-shaped, directed slightly adapically, parietal pad fairly large, not nodiform.

Surface only slightly glossy when fresh. Suture simple to crenulated (depending on rib alignment), shallow. Whorls convex with periphery at basal third of whorl, early whorls more strongly convex with median periphery, no distinct subsutural cord or sulcus, but on later whorls the axial ribs (which are suture-to-suture and sometimes continuous) are shallowly indented posteriorly to demarcate a subsutural convexity. Axial ribs strong, opisthocline, sinuous on last whorl, reaching rostrum, in t/s rounded-angular, wider than intervals, 7–8 ribs per whorl. Terminal varix strong, suture to base, slightly preceding outer lip. Microsculpture of growth lines and very faint, dense spiral striae. Rostrum with 4–8 declivous spiral ridges. Teleoconch whorls ca 5.7.

Protoconch narrowly domed, of ca 2.2 slightly convex, smooth, whorls, diameter 800 µm, height 650 µm.

Dark yellowish-brown, early part of spire paler, colour uniform except sometimes for a row of pale dots on ribs below indentation and 1–2 around base of last whorl, back of lip pale, varix with a pale yellowish blotch below suture.

Measurements. Holotype: 7.6 x 2.7 mm; largest and smallest paratypes: 9.4 x 3.3 mm and 7.2 x 3.0 mm, respectively. Largest non-type 9.9 x 3.2 mm.

Radula ( Fig. 24 C, D): Rachidian narrow, length more than three times exceeds width, anterior edge indistinct. Teeth with large single median cusp. Lateral teeth broad, arcuate, with 11 cusps, 2nd–4th from inner side being the longest and gradually diminishing in length towards outer side, where they evanesce. Marginal teeth relatively short and broad, with poorly pronounced blade, about 1/3 of teeth length. Blade edges not thickened. Accessory limb not pronounced. About 40 rows of teeth.

Remarks. Perhaps the most striking character of this inconspicuous little brown species is its variability, not only in proportions and colour pattern, but in development of axial ribs. In some examples the ribs appear strong and aligned, in others (even in the same shell) they alternate, thereby appearing weaker, and distinctly crenulating the suture.

There is some resemblance to Clavus quadrasi (Boettger, 1895) , but it lacks the high gloss of that, and has stronger ribs, which are indented below the suture. The similarly coloured species C. maestratii and C. aeneus (Hedley, 1922) have more convex whorls and a high gloss.

Figures

FIGURE 23. Clavus hylikos n. sp. A. B. Holotype; C. Paratype, MNHN IM – 2000 – 26941, SL 8.7 mm; D. Radula voucher, New Caledonia, EXPÉDITION MONTROUZIER, Touho Stn. 1260, SL 7.5 mm (radula—Fig. 24 C, D).

FIGURE 24. Radulae of Clavus devexistriatu s n. sp., C. hylicos n. sp. and C. maestratii n. sp. A, B. Clavus devexistriatus, New Caledonia, LAGON, Stn. 933, SL 12.8 mm (shell—Fig. 22 C); C, D. Clavus hylikos; New Caledonia, EXPÉDITION MONTROUZIER, Touho Stn. 1260, SL 7.5 mm (shell—Fig. 23 D). E, F. Clavus maestratii, EXPÉDITION MONTROUZIER, Koumac Stn. 1309, SL 9.8 mm (shell—Fig. 25 E).