Parvamussium conspectum Dijkstra & Kastoro, 1997
DIJKSTRA, H. H. & W. W. KASTORO. 1997. Mollusca Bivalvia: Pectinoidea (Propeamussidae and Pectinidae) from eastern Indonesia. In Crosnier, A. & Bouchet, P. (eds), Résultats des Campagnes MUSORSTOM, Volume 16. Mémoires du Muséum National d'Histoire naturelle 172: p. 245-285, figs. 1-159. [p. 258, figs. 48-61]
1997 Parvamussium conspectum Dijkstra & Kastoro, 1997
H. H. Dijkstra & W. W. Kastoro, 1997, figures 44-67.
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«Parvamussium sp. cf. texturatum - DIJKSTRA, 1991: 17, figs 44-52.
MATERIAL EXAMINED. — Indonesia. KARUBAR, Kai Islands: stn DW 02, 05°47'S, l32°13'E, 209-240 m, 1 lv (paratype POLIPI), 2 rv (paratypes HD, POLIPI). — Stn DW 15, 05°17'S, 132°41'E, 212-221 m, 1 spm. (holotype), 2 lv, 2 rv (paratypes MNHN) — Stn DW 18, 05°18'S, 133°01'E, 205-212 m, 1 lv (paratype HD). — stn DW 24, 05°32S, 132°51'E, 230-243 m, 2 lv (paratypes MNHN).
TYPE MATERIAL. — Holotype, live taken, MNHN. Paratypes: 2HD, 2 POLIPI, 5 MNHN.
TYPE LOCALITY. — Kai Islands, E Indonesia, KARUBAR, stn DW 15, 050°17'S, 132°41'E,212-221 m.
DISTRBUTION. — Eastern Indonesia; shells in 100-290 m, alive in 212-250 m.
DESCRIPTION. — Shell small, up to ca. 5 mm high, fragile, semi-transparent, valves equally convex, elongate, inequivalve, slightly inequilateral, auricles unequal in size, umbonal angle ca. 90°. Prodissoconch ca.190 μm in height. Left valve sculptured with ca. 20 primary and secondary inegularly spaced radial riblets, ca. 10 closely set commarginal lamellae in early growth stage (before pre-radial stage), widely spaced on central part of disc and more closely so towards ventral margin. Intersections of radial riblets and commarginal lamellae strongly squamous. Anterior auricle larger than posterior and provided with closely spaced, strongly irregularly developed concentric lamellae, more prominent anteriorly. A row of small lamellae produced near disc flank. Right valve sculptured with ca. 20 widely spaced concentric lamellose lirae. Sculpture of auricles similar to that of left valve. A radial lira on anterior auricle near byssal fasciole. Internal ribs 9, commencing 1 mm below resilifer and developed towards 0.5 mm above periphery, with a small auricular riblet on each side. Hinge line straight. Resilifer triangular. Byssal fasciole and notch small. Ctenolium absent. Left valve creamy-orange, right valve transparent white. Inner side of both valves glossy. Dimensions (holotype): H 5.1, L 4.7, D 1.1 mm.
REMARKS. — Parvamussiurn sp. cf. texturatum of DIJKSTRA (1991: 17, figs 44-52) differs from the present material only in the internal ribs being shorter and slightly more numerous (10 instead of 9). P. texturatum (Dautzenberg & Bavay, 1912) differs by having a more orbicular shape, a weaker sculpture of commarginal lamellae on the left valve, and in having more numerous internal ribs (15). P. vesiculatun Dijkstra, 1995, differs by having a more nodose sculpture at intersections on the left valve, more numerous closely spaced concentric lamellae on the right valve, and less developed internal riblets (only a few rudimentary near the anterior and posterior margins). P. undisonum Dijkstra, 1995 differs in size (larger, up to ca. 14 mm), is more oblique, and more weakly sculptured with more close-set commarginal lamellae on the left valve.
ETYMOLOGY. — Lat. conspectus, adj. = conspicuous.»
HENK H. DIJKSTRA & WORO W. KASTORO, 1997
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«Habitat. Living in the bathyal zone, free on soft sediment (sand and mud).
Distribution. Indonesia, 100–290 m (Dijkstra, 1991; Dijkstra & Kastoro, 1997). Maximum depth range of live-taken specimens is 212–290 m. Present specimens from eastern Australia dead in 187 m.
Remarks. This species is morphologically close to Parvamussium texturatum (Dautzenberg & Bavay, 1912), known from the Sulu Sea. Parvamussium texturatum is circular and P. conspectum more elongate in shape. Moreover, typical P. texturatum has more numerous internal riblets (15), P. conspectum fewer (9). The sculpture on the left valve of P. texturatum is somewhat weaker than that of P. conspectum.
The present specimens from the Great Barrier Reef are identical to the type specimens, apart from being somewhat more circular in shape, and some specimens have one more internal rib or one or two more rudimentary interstitial riblets. Moreover, typical specimens have somewhat more prominent commarginal lamellae in the early growth stage. Parvamussium conspectum is a new record for Australia.» DIJKSTRA, H. H. & A. G. BEU. 2018. Living scallops of Australia and adjacent waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae). Records of the Australian Museum, 70 (2): 113-330, figs. 1-102. [p. 133]
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Parvamussium conspectum Dijkstra & Kastoro,; H. H. Dijkstra & A. G. Beu, 2018, Living scallops of australia and adjacent waters, figures 7A-7E.
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