Cyclopecten reticulatus, Dijkstra & Beu, 2018

Dijkstra, Henk H. & Beu, Alan G., 2018, Living Scallops of Australia and Adjacent Waters (Mollusca: Bivalvia: Pectinoidea: Propeamussiidae, Cyclochlamydidae and Pectinidae), Records of the Australian Museum (Rec. Aust. Mus.) 70 (2), pp. 113-330 : 152

Cyclopecten reticulatus sp. nov.

Figs 16, 19A–D

Holotype (pr) (H 9.0 mm, W 9.9 mm, D 2.9 mm) AM C.572380, CORAL SEA, 11°35.61'S 145°29.42'E, alive, 1770–1863 m, benthic sled, leg. I. Loch, 22 Aug 1988 (ORV Franklin stn 14) . Paratypes (5 pr): 2 same data as holotype, AM C.572395, C.165220; 3 paratypes (2 AM C.165221 [in part], 1 ZMA Moll.409003): 11°40.98'S 145°36.85'E, alive, 2039–2052 m, benthic sled, ORV Franklin stn 15, coll. I. Loch, 23 Aug 1988. Part of the ventral marginal region of the left valve of the holotype is broken off (height originally somewhat larger than 9.0 mm) .

Description. Shell up to c. 10 mm high, fragile, semitranslucent white, almost circular, compressed, inequivalve, equilateral, left valve somewhat more convex than right, auricles unequal in shape and size, umbonal angle c. 110°, inner surface without riblets, smooth.

Left valve sculptured with prominent commarginal lamellae throughout, c. 5 per mm on central part of disc, somewhat more widely spaced in early growth stage and more narrowly near ventral margin, commencing at c. 1 mm shell height. Unevenly spaced radial riblets commence at c. 2 mm shell height and increase in number to ventral margin, c. 6 per mm on central part of disc. Commarginal sculpture coarse near ventral margin, radial sculpture weaker, near central part reticulate, near anterior margin intersections somewhat noduliferous, near ventral margin more lamellose. Auricles with closely spaced commarginal lamellae and 3–4 delicate radial riblets, anterior auricle larger than posterior. Dorsal margin straight.

Right valve with delicate commarginal lirae throughout, somewhat more closely spaced than on left valve. Anterior auricle with coarse commarginal lamellae, weaker and finer on posterior. Byssal notch relatively deep, byssal fasciole narrow.

Discussion. Cyclopecten reticulatus sp. nov. is most similar to Cyclopecten kermadecensis (E. A. Smith, 1885) from the Kermadec Islands , but differs in shape ( C. kermadecensis more oblong) and is sculptured with more widely spaced commarginal lamellae (more closely spaced and more radially sculptured in C. kermadecensis ) on the left valve. Cyclopecten horridus is smaller in size (c. 6 mm high) than the present species; both are almost circular in shape. Cyclopecten horridus has coarser radial sculpture on the left valve (weak on C. reticulatus ) and weaker commarginal sculpture (more prominent on C. reticulatus ) with hollow spines on the intersections (more noduliferous on C. reticulatus ). Cyclopecten pellucidulus Dijkstra, 1995 is somewhat similar in shape, but smaller in size than C. reticulatus sp. nov. (up to c. 6 mm in height, C. reticulatus c. 10 mm in height) and lacks radial sculpture on the left valve. Cyclopecten kapalae is also smaller in size (up to c. 6 mm in height) and somewhat more oblong than C. reticulatus , with more delicate reticulate sculpture on the left valve.

Habitat. Living in the bathyal and abyssal zones on soft sediment (sand and mud).

Distribution. Coral Sea, 11°35.61'–40.98'S 145°29.42'– 36.85'E. Present specimens alive in 1770–2052 m.

Remarks. The present species is not recorded from the Australian continental shelf.

Etymology. The specific name reflects the reticulate left valve (Latin, adj. reticulatus = a small net).