Cyclochlamys corrugata, Dijkstra & Maestrati, 2017

Dijkstra, Henk H. & Maestrati, Philippe, 2017, New species and new records of littoral and bathyal living Pectinoidea (Bivalvia: Propeamussiidae, Cyclochlamydidae, Pectinidae) from the western and southwestern Pacific, Zoosystema 39 (4), pp. 473-485 : 479-480

Cyclochlamys corrugata n. sp.

( Fig. 3 A-H)

TYPE MATERIAL. — Papua New Guinea. KAVIENG 2014, stn KB20, 02°45.2’S, 150°41.7’E, – 8 m, alive, 5 paratype spms ( MNHN- IM-2013-50881, 50883, 50885, 50887, 50889). — Stn KS35, 02°38.8’S, 150°40.7’E, 4-5 m, alive, 3 paratype spms ( MNHN- IM-2013-53544, 53545, 53547). — Stn KB66, 02°35.2’S, 150°50.3’E, – 17 m, alive, holotype spm (MNHN-IM-2013-55062). — Same stn, alive, 2 paratype spms (MNHN-IM-2013-55060, 55061).

OTHER MATERIAL. — Papua New Guinea. KAVIENG 2014, Stn KB08, 02°33.2’S, 150°48.2’E, – 13 m, 1 lv. — Stn KB10,

02°33.5’S, 150°47.4’E, – 13 m, alive, 2 spms (1 MNHN, 1 NBC). — Stn KB20, 02°45.2’S, 150°41.7’E, – 8 m, alive, 1 spm, 4 lv. — Stn KB34, 02°43.7’S, 150°37.1’E, – 43 m, 1 lv. — Stn KS35, 02°38.8’S, 150°40.7’E, 4-5 m, alive, 1 spm. — Stn KS61, 02°35.2’S, 150°43.1’E, 9-13 m, 3 lv. — Stn KS63, 02°45.2’S, 150°41.7’E, 10-12 m, alive, 2 spms, 4 lv. — Stn KB68, 02°45.2’S, 150°41.7’E, 22-27 m, 1 lv, 1 rv. — Stn KB74, 02°45.2’S, 150°44.5’E, – 20 m, alive, 1 spm. — PAPUA NIUGINI 2012, stn PB16, 05°04.7’S, 145°48.8’E, – 5 m, alive, 4 spms (3 MNHN, 1 NBC). — Stn PB40, 05°15.9’S, 145°47.1’E, 9-11 m, alive, 1 spm, 1 lv. — Stn PS41, 05°15.9’S, 145°47.1’E, – 10 m, 3 lv. — PD51, 05°10.1’S, 145°50.3’E, 3-12 m, 1 lv. — Stn PD63, 05°09.9’S, 145°48.3’E, 0-15 m, 1 lv. (MNHN).

TYPE LOCALITY. — Papua New Guinea, New Ireland, mainland, N-coast, 02°35.2’S, 150°50.3’E, – 17 m, alive in sand and rubble, 24.VI.2014 (KAVIENG 2014, stn KB66).

ETYMOLOGY. — Left valve commarginally wrinkled and ruffled (Latin corrugata , adjective meaning wrinkled or ruffled).

DISTRIBUTION. — Papua New Guinea, live in 4-20 m (maximum depth range), 5-20 m (minimum depth range).

DESCRIPTION

Shell

Up to 2.8 mm high, fragile, strongly posteriorly oblique, inequivalve, inequilaterial, wider than high, lv opaque whitish, rv translucent. Shape irregular, variable, typically changing during ontogeny, commonly associated with change in spacing of commarginal lamellae (habitat constriction).

Prodissoconch

220 µm long, lv larval shell conical and granular, rv larval shell almost flat with irregularly spaced ridges and weak radial grooves.

Left valve

Disc with 3-6 weak radial plicae, lacking in some specimens, in early ontogeny smooth (c. 0.3-0.5 mm high), after that very closely spaced commarginal lamellae commence and develop to the periphery; on lamellae, very closely set small nodules present at intersections, resembling pearl strands; auricles similarly sculptured and continuous with disc, posterior auricle distinctly larger than anterior; interlamellar spaces narrow, with very closely spaced radial threads with convex crests, lacking in some specimens; ventral margin weakly angular to slightly convex.

Right valve

Disc and all but dorsal border of posterior auricle with outer layer of commarginal hexagonal prisms, more elongate in late ontogeny. Posterior auricle continuous with disc, smooth; anterior auricle distinctly demarcated from disc with 3-4 nodulous radial threads. Byssal notch of moderate depth, byssal fasciole rather broad.

Dimension of holotype

H 2.8 mm, W 3.4 mm, D 0.9 mm. REMARKS

The present species resembles three congeneric species, viz. Cyclochlamys nepeanensis (Pritchard & Gatliff, 1904) , known from southeastern and southern Australia, Cyclochlamys incubata ( Hayami & Kase, 1993) from Japan, and Cyclochlamys irregularis Dijkstra & Marshall, 2008 from New Zealand. All of these species have nodules on the intersections of the commarginal lamellae and radial riblets of the left valve, although much more widely spaced than on the left valve of the present species ( C. corrugata n. sp. combined together, C. nepeanensis , C. incubata , and C. irregularis with strongly variable interspaces, 6-10 per mm on central part of disc). Moreover, the shape of C. corrugata n. sp. is strongly posteriorly oblique and in most specimens with a more or less angular ventral margin, with angulations caused by the radial plicae ( C. nepeanensis is circular, C. incubata weakly posteriorly oblique, and C. irregularis circular to slightly posteriorly oblique; all lack radial plicae).

Smooth specimens from stn KB50 (lv) and KS61 (2 lv) are close to or a smooth variant of C. corrugata n. sp., viz. the faint granular sculpture on the anterior auricle of the left valve of stn KB50 is very similar to that of C. corrugata n. sp.

Figures

FIG. 3. — A-H, holotype of Cyclochlamys corrugata n. sp. (MNHN-IM-2013-55062); A, exterior rv; B, interior rv; C, exterior lv; D, interior lv; E, prodissoconch and early ontogeny of lv shell disc; F, prodissoconch and early ontogeny of rv shell disc; G, exterior detail lv; H, exterior detail rv. Abbreviations: see Material and methods. Scale bars: A-D, 500 µm; E, F, G, H, 100 µm.