Cyclopecten comptulus, Dijkstra & Maestrati, 2013

Dijkstra, Henk H. & Maestrati, Philippe, 2013, Pectinoidea (Bivalvia: Propeamussiidae, Entoliidae and Pectinidae) from the Tarava Seamounts, Society Islands and the Tuamotu Archipelago (French Polynesia), Zoosystema 35 (3), pp. 361-375 : 368-370

Cyclopecten comptulus n. sp.

(Fig. 4)

TYPE MATERIAL. — Society Islands . Tarasoc, stn CP 3415, 16˚34’S, 151˚47’W, 614-730 m, alive, holotype spm ( MNHN 25706 ) ; stn DW 3434, 16˚42’S, 151˚03’W, 700-785 m, alive, paratype spm ( ZMA Moll. 398325) .

TYPE LOCALITY. — Society Islands, Bora Bora, 16˚34’S, 151˚47’W, 614-730 m (Tarasoc, stn CP 3415).

ETYMOLOGY. — Shell somewhat overdressed (Latin: comptulus , adjective meaning dressed up).

DISTRIBUTION. — Society Islands, living in 700-730 m (minimum depth range).

DESCRIPTION

Shell up to c. 25 mm in height, fragile, opaque to semi-transparent, whitish, almost circular, inequivalve, nearly equilateral, weakly inflated, left valve slightly more convex than right valve, auricles unequal in shape and nearly equal in size (anterior slightly larger than posterior).Prodissoconch 250 µm long.

Left valve sculptured with strongly developed, closely spaced, commarginal undulated lamellae and laterally closely arranged radial rows of imbricated vesicles (damaged on many specimens), which are part of the commarginal lamellate sculpture, commencing at 1 mm from dorsal margin. Auricles sculptured with prominent, closely spaced, commarginal lamellae forming hollow bands on anterior auricle and radial vesicular sculpture on posterior auricle, continuous with posterior part of disc.

Right valve with sculpture similar to left valve, although somewhat weaker and more closely spaced and with more radial rows of vesicular sculpture. Marginal apron, pressed against left valve, partly broken off. Anterior auricle with very closely spaced commarginal lamellae, posterior more coarsely sculptured with radial rows of vesicles, continuous with disc. Hinge line straight. Byssal notch shallow, byssal fasciole and ctenolium lacking. Very weak interior radial grooves throughout on left valve (c. 20), lacking on right valve. Interior riblets lacking.

Dimensions of the holotype: H 25.4 mm, W 25.0 mm, D 5.9 mm.

REMARKS

The morphologically closest resembling congeneric species is Cyclopecten kermadecensis (E. A. Smith, 1885) , recorded from the Kermadec Islands ( Dijkstra & Marshall 2008: 18). Cyclopecten kermadecensis differs from Cyclopecten comptulus n. sp. in size ( C. kermadecensis up to c. 7.5 mm in height, C. comp-

FIG. 4. — Cyclopecten comptulus n. sp.: A, holotype, external view of the left valve; B, holotype, internal view of the left valve; C, holotype, external view of the right valve; D, holotype, internal view of the right valve; E, prodissoconch of the left valve; F, details of the right valve; G, details of the left valve. Scale bars: A-D, 1 cm; E, 50 µm; F, G, 5 mm.

tulus n. sp. up to c. 25 mm), in sculpture of the left valve ( C. kermadecensis has delicate closely spaced commarginal ridges in early growth stage on the left valve, in C. comptulus n. sp. coarser and wider spaced; C. kermadecensis has rather regularly spaced, outwardly sloping commarginal lamellae with radially arranged hollow vesicles ( Dijkstra & Marshall 2008: fig. 16D) in late growth stage, in C. comptulus n. sp. more irregularly spaced with outwardly sloping coarse undulated lamellae), and also in sculpture of the right valve ( C.kermadecensis has regularly spaced, outwardly sloping commarginal ridges [ Dijkstra & Marshall 2008: fig. 16E], C. comptulus n. sp. has very closely spaced, outwardly sloping roughly formed lamellae). The undulated commarginal lamellae in the early growth stage make Parvamussium undisonum Dijkstra, 1995 similar to the present species, but other characters are different, in size ( P. undisonum up to c. 14 mm in height, C. comptulus n. sp. up to c. 25 mm), in shape ( P. undisonum slightly elongate, C. comptulus n. sp. circular), in sculpture on the left valve ( P. undisonum has radial riblets, C. comptu- lus n. sp. has radial vesicles), and in internal riblets ( P.undisonum has nine-ten plus some rudimentary, lacking in C. comptulus n. sp.).

Commarginal sculpture and radial rows of vesicles are also present on the left valve of P.lamellatum n. sp., but other morphological characters are different, i.e. in size ( P.lamellatum n. sp. up to c. 10 mm in height, C. comptulus n. sp. up to 25 mm), in sculpture on the left valve ( P.lamellatum n. sp. has a more delicate and more closely spaced commarginal sculpture, on C. comptulus n. sp. coarser and more widely spaced), and in internal riblets ( P.lamellatum n. sp. has ten plus one or two rudimentary,lacking in C.comptulus n.sp.).

Family ENTOLIIDAE Teppner, 1922