Cyclochlamys aperta, Dijkstra & Maestrati, 2012

Dijkstra, Henk H. & Maestrati, Philippe, 2012, Pectinoidea (Mollusca, Bivalvia, Propeamussiidae, Cyclochlamydidae n. fam., Entoliidae and Pectinidae) from the Vanuatu Archipelago, Zoosystema 34 (2), pp. 389-408 : 394

Cyclochlamys aperta n. sp. ( Fig. 1 A-E)

TYPE MATERIAL. — Vanuatu. SANTO 2006, stn DS93, 15°33.6’S, 167°16.5’E, 70 m, holotype spm ( MNHN 24271 ). — Stn DS104, 15°34.1’S, 167°16.0’E, 10-80 m, 2 paratypes lv ( MNHN 24272 ).

TYPE LOCALITY. — Vanuatu Archipelago, west of Tutuba Island , 15°33.6’S, 167°16.5’E, 70 m (SANTO 2006 stn DS93) .

DISTRIBUTION. — Known only from the type locality, alive at 70 m depth.

ETYMOLOGY. — A micro-scallop with a smooth disc (Latin “apertus”, adjective meaning uncovered or laevis).

DESCRIPTION

Shell up to c. 1.20 mm high, fragile, posteriorly oblique, inequivalve, inequilateral, left valve more inflated than right valve, wider than high, translucent.

Left valve disc and auricles smooth with a few commarginal growth lines. Posterior auricle slightly larger than anterior one. Prodissoconch c. 310 µm wide, conical, sculptured with crisp radial threads.

Right valve disc and ventral half of posterior auricle with outer layer of commarginally elongate, hexagonal prisms that form broad, flexible ventral apron. Anterior auricle with three weak radial threads with small tubercles. Byssal notch moderately deep.

Dimensions of holotype: H 1.2 mm, W 1.8 mm, D 0.8 mm.

REMARKS

Cyclochlamys aperta n. sp. is morphologically closest to Cyclochlamys australense Dijkstra & Maestrati, 2010 , from the Austral Islands (lives in 3-52 m).Both species are almost the same size ( C. aperta n. sp. 1.2 mm in height, C. australense 1.8 mm), and are posteriorly oblique. However, C. aperta n. sp. is almost smooth with only a few very weak commarginal growth lines. Cyclochlamys australense has a commarginal vesicular sculpture in late growth stage.

Figures

FIG. 1. — A-E, Holotype of Cyclochlamys aperta n. sp. (MNHN 24271); A, B, external views of left and right valve; C, left valve prodissoconch; D, right valve detail; E, right valve prodissoconch; F-J, Micropecten excuratus n. gen., n. sp.; F, holotype (MNHN 24273), external view of left valve; G, paratype (MNHN 24274), external view of right valve; H, holotype, left valve prodissoconch; I, paratype, right valve detail; J, paratype, right valve prodissoconch. Scale bars: A, B, F, G, 500 µm; C-E, H-J, 100 µm.