Parvamussium marquesanum Dijkstra & Maestrati, 2008
DIJKSTRA, H. H. & P. MAESTRATI. 2008. New species and new records of deep-water Pectinoidea (Bivalvia: Propeamusiidae, Entoliidae and Pectinidae) from the South Pacific. In: V. Héros, R. H. Cowie & P. Bouchet (Eds.), Tropical Deep-Sea Benthos 25. Mémoires du Muséum national d'Histoire naturelle, 196: 77-113, figs. 1-55. Paris [p. 89, figs. 20-25]
2008 Parvamussium marquesanum Dijkstra & Maestrati, 2008
H. H. Dijkstra & P. Maestrati, 2008, figures 20-31.
|
«TYPE MATERIAL. — Holotype (spm) MNHN 20455 and 8 paratypes MNHN 20456-20458, 1 HD.
TYPE LOCALITY. — Marquesas Islands, Eiao, 07˚55’S, 140˚44’W, 660-680 m [MUSORSTOM 9: stn CP 1272].
MATERIAL EXAMINED. — Marquesas. MUSORSTOM 9: stn CP 1271, 07˚54’S, 140˚42’W, 600 m, 2 spms, 1 lv, 1 rv (paratypes MNHN 20456); stn CP 1272, 07˚55’S, 140˚44’W, 660-680 m, 5 spms (holotype MNHN 20455 and 3 paratypes MNHN 20457, 1 HD); stn CP 1307, 08˚58’S, 140˚16’W, 708-738 m, 1 spm (paratype MNHN 20458).
DISTRIBUTION. — Marquesas Islands; live in 600-708 m.
DESCRIPTION. — Shell up to c. 13 mm in height, fragile, opaque to semi-transparent, flattened, left valve slightly more convex than right valve, nearly circular, slightly wider than high, inequivalve, sculpture of left valve somewhat reticulated, right valve commarginally sculptured, equilateral, auricles unequal in shape and size (anterior larger than posterior).
Left valve sculptured with delicate commarginal lamellae (somewhat curled ventrally), commencing at c. 2 mm from umbonal margin, widely spaced (c. 0.8 mm apart), extending to the ventral margin, closely spaced (c. 0.1 mm apart) and prominently sculptured near the margin. Lamellae overrun irregularly spaced, delicate radial lirae (c. 8 per mm over central part of disc). Anterior auricle with wider set, more prominent commarginal lamellae than posterior. Right valve with closely spaced, regularly arranged commarginal lirae, weak in early growth stage, more lamellated near ventral margin. Marginal apron (c. 1 mm wide) pressed to left valve. Auricles with closely spaced, prominent commarginal lamellae. Hinge line straight. Byssal notch moderately deep and small, byssal fasciole narrow. Internally 11 radial ribs, commencing 3 mm from umbonal margin, extending to marginal apron. Dimensions of holotype: H 12.8, W 12.9, D 3.3. REMARKS. — Parvamussium multiliratum Dijkstra, 1995 is a somewhat similar bathyal species, known from New Caledonia (Dijkstra 1995: 26), Wallis and Futuna and Vanuatu (Dijkstra 2001: 83). The two species are similar in shape (circular) and in the lamellar sculpture of the left valve, but can be differentiated by the following characters:
P. marquesanum P. multiliratum
Height c. 13 mm c. 9 mm
Sculpture lv reticulate commarginal lamellae Internal ribs 11 (coarse) 14+ (delicate) Parvamussium retiaculum Dijkstra, 1995, known from similar localities to P. multiliratum and from the Norfolk Ridge and Kermadec Islands (Dijkstra & Marshall 1997: 81), has somewhat similar internal ribs and reticulate sculpture on the left valve but differs from P. marquesanum in having an elongate shape (higher than wide), a smaller size (up to c. 7 mm in height) and a larger anterior auricle with more prominent sculpture.
ETYMOLOGY. — After the Marquesas Islands.»
HENK H. DIJKSTRA & PHILIPPE MAESTRATI, 2008
|