Cyclochlamys barbatula, 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 : 480-482

Cyclochlamys barbatula n. sp.

( Fig. 4 A-H)

TYPE MATERIAL. — Papua New Guinea. KAVIENG 2014, stn KB36, 02°38.8’S, 150°38.4’E, 3-8 m, alive, paratype spm ( MNHN- IM-2000-33117). — Stn KB08,‰ 2°33.2’S, 150°48.2’E, – 13 m, paratype lv (MNHN-IM-2000-33114). — Stn KS09, 02°36.1’S, 150°45.9’E, 15-16 m, paratype lv (MNHN-IM-2000-33112). — Stn KS35, 02°38.8’S, 150°40.7’E, 4-5 m, paratype lv ( MNHN- IM-2000-33113). — Stn KB60,‰ 2°32.5’S, 150°35.3’E, – 20 m, alive, holotype spm (MNHN-IM-2000-33116), 2 paratypes spms (MNHN-IM-2013-55047, 55049), 3 paratypes spm + 2 lv (4 MNHN-IM-2000-33115, RMNH.MOL.290719).

TYPE LOCALITY. — Papua New Guinea, Kavieng Lagoon, N-side of Wadei Island, 02°38.8’S, 150°38.4’E, 3-8 m, alive in sand and rubble slope, 13.06.2014 (KAVIENG 2014), stn KB36.

OTHER MATERIAL EXAMINED. — Papua New Guinea. MADANG LAGOON (PAPUA NIUGINI 2012), stn PB47, 05°11.3’S, 145°49.6’E, 5 m, alive, 1 spm, 1 rv (MNHN-IM-2013-6365).

ETYMOLOGY. — Left valve sculptured with strong commarginal lamellae like little fringes (Latin barbatula , adjective meaning with a fringe).

DISTRIBUTION. — Papua New Guinea, live in 3-20 m (maximum depth range), 8-20 m (minimum depth range).

DESCRIPTION

Shell

Up to 1.5 mm high, fragile, strongly posteriorly oblique, inequivalve, inequilaterial, wider than high, posterior auricle larger than anterior auricle, translucent whitish. Shape somewhat irregular, variable, typically changing during ontogeny, commonly associated with change in spacing of commarginal lamellae (habitat constriction).

Prodissoconch

235 µm long, lv larval shell conical, with reticulate sculpture, rv larval shell slightly raised, also with reticulate sculpture, in dissoconch stage radially sculptured with irregularly spaced ridges.

Left valve

With smooth disc in early ontogeny (c. up to 0.4-0.6 mm), after that there is a strong reticulate scupture commences, consisting of widely spaced commarginal lamellae and weaker radial riblets (c. 4-5 per mm on central part of disc), developing to the periphery; on lamellae prominent hollow nodules (c. 3-4 per mm) present on intersections of radial and com- marginal sculpture. Auricles with similar, more closely spaced reticulate sculpture; continuous with disc.

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 separated from disc, with 4-5 delicate, nodulous radial threads. Byssal notch of moderate depth, byssal fasciole rather broad.

Dimension of holotype

H 1.5 mm, W 1.7 mm, D 0.6 mm. REMARKS

The present species resembles its congener Cyclochlamys incubata ( Hayami & Kase, 1993: figs 202-212), known from littoral Japanese waters, in the shape of the shell disc and the reticulate sculpture on the left valve. However C. barbatula n. sp. differs from C. incubata by having a smooth disc in early ontogeny ( C. incubata has radial threads immediately after the dissoconch stage), by having more prominent and more widely arranged commarginal and radial sculpture with more strongly developed hollow nodules or vesicles on the crests ( C. incubata with weaker solid nodules).

A somewhat superficially similar congener is Cyclochlamys irregularis Dijkstra & Marshall, 2008 , known from littoral to bathyal waters (shells only) of northern New Zealand. Cyclochlamys barbatula n. sp. differs from C. irregularis in size ( C. barbatula n. sp. up to c. 1.5 mm high, C. irregularis up to c. 3 mm), in having a much more posteriorly oblique outline ( C. irregularis circular to weakly posteriorly oblique), by having a more acutely conical prodissoconch ( C. irregularis more roundly conical), by having a smooth dissoconch ( C. irregularis sculptured with crisp delicate commarginal and radial sculpture), and by having more prominent and widely spaced reticulate sculpture on the left valve.

Figures

FIG. 4. — A, B, E-H, holotype of Cyclochlamys barbatula n. sp. (MNHN-IM-2000-33116): A, exterior lv; B, exterior rv; C, D, paratype (MNHN-IM-2013-55047); C, interior rv; D, interior lv; E, prodissoconch and early ontogeny of rv shell disc; F, prodissoconch and early ontogeny of lv shell disc; G, exterior detail lv; H, exterior detail rv; I-P, Holotype of Micropecten reticulatus n. sp. (MNHN-IM-2013-50885): I, exterior rv; J, interior rv; K, exterior lv; L, interior lv; M, prodissoconch and early ontogeny of lv shell disc; N, prodissoconch and early ontogeny of rv shell disc; O, exterior detail lv; P, exterior detail rv. Abbreviations: see Material and methods. Scale bars: A-D, I-L, 500 µm; E-H, M, N, 100 µm; O, P, 50 µm.