Micropecten reticulatus, 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 : 482

Micropecten reticulatus n. sp.

( Fig. 4 I-P)

TYPE MATERIAL. — Papua New Guinea. KAVIENG 2014, stn KB20, 02°45.2’S, 150°41.7’E, 8 m, alive, holotype spm ( MNHN- IM-2013-50885). — Same data, 4 paratype spms ( MNHN- IM-2013-50879, 50884, 50886, 50888. — Stn KB60, 02°32.5’S, 150°35.3’E, 20 m, alive, paratype spm (MNHN-IM-2013-55048). — Stn KS61, 02°35.2’S, 150°43.1’E, 9-13 m, 3 lv paratypes (2 MNHN- IM-2000-33118, 1 RMNH.MOL.290914).

TYPE LOCALITY. — Papua New Guinea, Kavieng Lagoon, S-coast of Baudison Island, 02°45.2’S, 150°41.7’E, – 8 m, live, wall with large ledges, 09.VI.2014 (KAVIENG 2014), stn KB20.

ETYMOLOGY. — Left valve with reticulate shell disc (Latin reticulatus , adjective meaning made like a net; with a hair-net).

DISTRIBUTION. — Papua New Guinea, live in 8- 20 m.

DESCRIPTION

Shell

Up to c. 2.1 mm high, fragile, hyaline, circular to slightly posteriorly oblique, inequivalve, almost equilateral, left valve more inflated than right valve; translucent whitish.

Prodissoconch

280 µm long, lv larval shell conical and with granular sculpture, rv larval shell flat, also granular, in dissoconch stage more radially sculptured with irregularly spaced ridges.

Left valve

Left valve disc and auricles sculptured with numerous narrow antimarginal lirae, secondary riblets in interspaces increasing to periphery, and delicate closely spaced commarginal lirae of similar strength to antimarginal ones, commencing in early growth stage (c. 0.5-0.8 mm below umbonal top). Auricles subequal, anterior slightly larger than posterior.

Right valve

Right valve disc and ventral half of posterior auricle similarly sculptured with very narrow antimarginal threads. Delicate hexagonal microstructure of simple calcite prismatic outer layer. Posterior auricle continuous with disc, anterior auricle demarcated, sculptured with a 3-4 fine nodulous radial riblets, spinose on dorsal margin. Byssal notch relatively deep, byssal fasciole broad.

Dimension of holotype

H 1.8 mm, W 1.8 mm, D 0.6 mm.

REMARKS

The most closely similar congener is Micropecten excuratus Dijkstra & Maestrati, 2012 , known from shallow waters around the Vanuatu Archipelago and the Berau Islands (see Dijkstra & Moolenbeek 2008: 17-18, figs 5-6, as “ Cyclochlamys sp.”). Micropecten reticulatus n. sp. and M. excuratus are similar in size and shape, and their reticulate sculpture on the left valve is matching more or less. Micropecten reticulatus n. sp. has slightly more prominent sculpture with small, solid nodules on the crests, whereas M. excuratus has weaker sculpture with more irregularly spaced commarginal lirae. Micropecten reticulatus has very delicate antimarginal sculpture on the right valve, consisting of numerous fine threads, whereas M. excuratus has more prominent antimarginal sculpture of more strongly developed ridges. Another similar congener is Micropecten plectofilum ( Oliver & Holmes, 2004) , known from shallow waters around Rodrigues (Indian Ocean). Micropecten reticulatus n. sp. differsfrom M. plectofilum by having regularly developed reticulate sculpture on the left valve, whereas M. plectofilum has irregularly spaced antimarginal sculpture with weaker commarginal threads. Micropecten reticulatus n. sp. also has very delicate, closely spaced antimarginal sculpture throughout on the right valve, whereas M. plectofilum has more prominent, widely spaced antimarginal riblets in late ontogeny.

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.