Epicodakia nodulosa, Glover & Taylor, 2007

Glover, Emily A. & Taylor, John D., 2007, Diversity of chemosymbiotic bivalves on coral reefs: Lucinidae (Mollusca, Bivalvia) of New Caledonia and Lifou, Zoosystema 29 (1), pp. 109-181 : 138-142

Epicodakia nodulosa n. sp.

( Figs 18C ; 19 )

Codakia reevei – Hedley 1909: 426. “ Lucina ” reevei – Lamprell & Whitehead 1992: pl. 20, fig. 124.

TYPE MATERIAL. — Holotype: 1 sh, L 16.6 mm, H 15.2 mm, T 4.0 mm ( MNHN).

Paratypes: Loyalty Islands, Lifou, Baie du Santal, stn 1421, 20°52.4’S, 167°08.5’E, 1 sh, L 12.5, H 11.1 mm, T 2.7 mm ( BMNH 20050572 ). — Atoll de Surprise , stn 449, 18°22’S, 163°09’E, 21 m 2 sh, L 14.2 mm, H 12.8 mm,T 3.2 mm ; L 11.5 mm, H 9.6 mm,T 2.5 mm ( MNHN).

TYPE LOCALITY. — New Caledonia, Koumac, Chenal de l’Infernet, stn 1304, 20°38.6’S, 164°13.2’E, 12- 15 m.

ETYMOLOGY. — Nodulosa refers to the nodulose sculpture.

MATERIAL EXAMINED. — Koumac. 3 stn, 0-15 m, 6 v. Lifou. 11 stn, 4-30 m, 14 v. Chesterfield Islands. CHALCAL 1, stn DC 17, 19°12’S, 158°56’E, 44 m, 1 sh. — Stn DC 24, 19°11’S, 158°11’E, 38 m, 2 v. CORAIL 2, stn DW 31, 19°25’S, 158°45’E, 57 m, 1 v. — Stn DW 40, 19°30’S, 158°35’E, 58 m, 1 v. — Stn DW 42, 19°22’S, 158°29’E, 45 m, 5 v. — Stn DW 44, 19°22’S, 158°23’E, 40 m, 1 v. — Stn DW 60, 19°15’S, 158°57’E, 45 m, 3 v. — Stn DW 72, 19°15’S, 158°21’E, 32 m, 2 v. — Stn DW 73, 19°12’S, 158°23’E, 41 m, 2 v. — Stn DW 76, 19°12’S, 158°33’E, 53 m, 1 v. — Stn DW 87, 19°06’S, 158°60’E, 31 m, 1 v. — Stn DW 94, 19°06’S, 158°50’E, 36 m, 3 v. — Stn DW 96, 19°06’S, 158°42’E, 41 m, 1 v. — Stn DW 101, 19°09’S, 158°26’E, 37 m, 5 v. — Stn DW 110, 19°09’S, 158°56’E, 40 m, 1 v. — Stn DW 122, 19°28’S, 158°17’E, 32 m, 2 v. — Stn DW 126, 19°28’S, 158°27’E, 46 m, 1 sh. — Stn DW133, 19°31’S, 158°25’E, 45 m, 1 v. — Stn DW 155, 19°49’S, 158°25’E, 42 m, 1 v. — Stn DW 156, 19°49’S, 158°21’E, 42 m, 2 v. — Stn DW 160, 19°46’S, 158°23’E, 35 m, 1 v. — Stn DW 163, 19°42’S, 158°16’E, 23 m, 1 v.

Other New Caledonia. LAGON, stn 60, secteur de Nouméa, 22°12’S, 166°11’E, 1 m, 2 v. — Stn 449, Atoll de Surprise, 18°22’S, 163°09’E, 21 m, 1 v. — Stn 1063, secteur des Belep, 20°03’S, 163°47’E, 31 m, 3 v. — Stn 1088, 19°46’S, 163°58’E, 23 m, 1 v. — Stn 1096, 19°51.4’S, 163°41’E, 27 m, 3 v. — Stn 1104, 19°42’S, 163°59’E, 22 m, 3 v. — Stn 1105, 19°40’S, 163°57’E, 25 m, 5 v. — Stn 1118, 19°35’S, 163°52’E, 30 m, 2 v. — Stn 1154, 19°09’S, 163°19’E, 40 m, 1 v. — Stn 1158, 19°10’S, 163°07’E, 48 m, 1 v. — Stn DW 1396, 18°21’S, 16305’E, 39 m, 1 v.

Loyalty Islands. MUSORSTOM 6, stn DW 433, 20°20’S, 169°09’E, 24 m, 1 v. — Stn DW 435, 20°21’S, 166°08’E, 32 m, 6 v. — Stn DW 436, 20°20’S, 166°07’E, 33 m, 1 v.

Australia. Big Sandy Cay, Swain Reefs, Queensland, 21°48’S, 151°52’E, 10 m ( AMS C.066765).

DISTRIBUTION. — Australia (Great Barrier Reef), Irian Jaya, Solomon Islands, New Caledonia.

DESCRIPTION

Shell medium size, H to 15.2 mm, L to 16.6 mm, ovate, longer than high, H/L 0.90, not inflated, T/L 0.22, yellow to white. Anteriorly extended, low umbones lie posterior of centre. Sculpture of around 20 strong, rounded, radial ribs separated by wide interspaces. Ribs crossed by regular commarginal lamellae producing thick scales or nodules on summits ( Fig. 19E ). Lamellae thinner and less prominent in interspaces between ribs. Periostracum surface micro-vesicular ( Fig. 19H ). Lunule long, shallow, lanceolate, slightly asymmetrical. Ligament short, external, set in shallow groove. RV with two cardinal teeth, the posterior larger and slightly bifid; single anterior and posterior lateral teeth. LV with two cardinals and two anterior and posterior lateral teeth. Anterior adductor muscle scar medium long, detached from pallial line for about 2/3 of length. Posterior adductor scar small, ovate. Pallial line entire. Shell interior radially undulose with impressions of ribbing; shell outside pallial line glossy with smooth margin.

REMARKS

Although this species has been occasionally referred to as “ Lucina ” reevei Deshayes (e.g., Hedley 1909; Lamprell & Whitehead 1992), the original description of Lucina reevei Deshayes, 1863 (pl. 3, figs 8, 9), from Réunion (holotype MNHN) is of a Ctena species with strong, bifurcating radial ribs and an inset, triangular ligament. Epicodakia nodulosa n. sp. is most similar to E. sweeti but has fewer radial ribs (20 vs. 40) that are crossed by more widely spaced, commarginal lamellae that produce thick, nodulose scales on the ribs.

Epicodakia sweeti ( Hedley, 1899) ( Figs 18B ; 20 )

Cardita sweeti Hedley, 1899: 495 , fig. 5.

Ctena transversa Dall, Bartsch & Rehder, 1938: 131 , pl. 35, figs 9-12.

Epicodakia sweeti – Paulay 2003: 233.

TYPE MATERIAL. — Cardita sweeti : holotype, 1 sh, L 13.9 mm, H 12.2 mm, T 4.2 mm ( NMV F27464C). Ctena transversa : holotype, off Waikiki, Oahu, Hawaiian Islands ( USNM 337409).

TYPE LOCALITY. — Funafuti Atoll, Tuvalu.

MATERIAL EXAMINED. — Koumac. 3 stn, 12-120 m, 3 v. Touho. 3 stn, 0-35 m, 8 v. Lifou. 9 stn, 0-30 m, 16 v. Other New Caledonia. LAGON, stn 383, Grand Récif Sud, 22°32’S, 167°13’E, 62 m, 1 v. — Stn 1104, secteur de Belep, 19°42’S, 163°59’E, 22 m, 1 v. Chesterfield Islands. CORAIL 2, stn DW 09, 20°53’S, 161°35’E, 62 m, 1 v. — Stn DW 60, 19°15’S, 158°57’E, 45 m, 1 v. — Stn DW 136, 19°31’S, 158°16’E, 37 m, 2 v. — Stn DW 144, 19°28’S, 158°23’E, 50 m, 2 v.

DISTRIBUTION. — Amirante Islands (Indian Ocean), Bali, Great Barrier Reef, Hawaii, Marquesas.

DESCRIPTION

Shell medium sized, white or yellowish; H to 17.0 mm, L to 18.3 mm, oval, longer than high, moderately inflated, T/L 0.27. Sculpture of about 40 closely-spaced, rarely bifurcate, radial ribs that become more widely-spaced, asymmetric and steeper to anterior. Ribs crossed by closely spaced commarginal lamellae, producing low, regular, rounded scales on summits of ribs ( Fig. 20F ). Lunule shallow, lanceolate, slightly asymmetrical, RV protruding. Ligament short, external. Hinge plate narrow, RV with 2 cardinal teeth, large posterior cardinal bifurcate, with single anterior and posterior lateral teeth. LV with 2 cardinal teeth, larger is bifurcate, and 2 anterior and posterior laterals. Anterior adductor muscle scar medium long, detached for half of length. Pallial line entire. Shell outside pallial line fluted from impression of ribbing, glossy, margin finely denticulate.

REMARKS

This species is similar in shape and hinge characters to E. consettiana but can be easily distinguished by the fewer and more prominent radial ribs. The other Epicodakia species from New Caledonia, E. nodulosa n. sp., has fewer ribs (around 20) than E. sweeti as well as distinctive nodulose scales.

From the original illustration, Lucina minuata Deshayes, 1863 (p. 20, pl. 3, figs 4, 5), from Réunion, appears similar to E. sweeti , but the figured specimen is not same as the putative type specimen (MNHN) which is a Ctena species resembling C. bella (also see Lamy 1921: 258).

Figures

FIG. 18. — Outline drawings of interiors of right valves of Epicodakia Iredale,1930 species:A, E. consettiana Iredale,1930; B, E. sweeti (Hedley, 1899); C, E. nodulosa n. sp. Not to scale.

FIG. 19. — Epicodakia nodulosa n. sp.: A-D, holotype (MNHN), Koumac, stn 1304, Chenal de l’Infernet, New Caledonia; A, B, exterior of right and left valves; C, D, interior of left and right valves;E, paratype,detail of anterior sculpture;F, G, paratype (BMNH 20050572), Lifou, stn 1421, details of hinge teeth; H, detail of shell surface. Scale bars: A-D, 10 mm; E, 1 mm; F, G, 2 mm; H, 100 µm.

FIG. 20. — Epicodakia sweeti (Hedley, 1899): A, B, holotype, Funafuti (NMV F27464C), exterior of right valve and interior of left valve; C, exterior of right valve, Grand Récif du Sud, New Caledonia, stn 383, 22°32’S, 167°13’E, 62 m (MNHN); D, detail of sculpture of C; E, F, interior of left and right valves of C; G, H, details of hinge teeth of D and E. Scale bars: A-C, E, F, 10 mm; D, 500 µm; G, H, 2 µm.