Myrtina reflexa, Taylor, John D. & Glover, Emily A., 2013

Taylor, John D. & Glover, Emily A., 2013, New lucinid bivalves from shallow and deeper water of the Indian and West Pacific Oceans (Mollusca, Bivalvia, Lucinidae), ZooKeys 326, pp. 69-90 : 80-81

Myrtina reflexa sp. n. Figs 9B, 11

Lucina inanis ( Prashad 1932) - Knudsen 1967: 286, pl. 2 figs 9,11. (non Prashad 1932).

Lucina inanis ' Prashad’ - Cosel and Bouchet 2008: 188, figs 55 A–F.

Type material.

Holotype: 1 whole shell, L 10.5 mm, H 9.4 mm, T 2.5 mm, NHMUK 1968738, John Murray Expedition stn 125, 825m, 5°36'12"S, 39°28'24"E off Zanzibar.

Paratypes: 2 RV, L 10.7 mm H 9.5 mm T 2.5 mm, L 11.8 mm H 10.7 mm T 2.8 mm, NHMUK 1968738 locality as holotype; 17 valves (13 RV, 4 LV), figured paratype (Fig. 11E-F) RV, L 15 mm, H 13.3 mm, NHMUK 20130121, John Murray Expedition stn 106, 183-194 m, 5°38'54"S, 39°18'42"E, off Zanzibar.

Other material.

1 whole shell (live collected) L 14.2 mm, H 12.7 mm, T 3.3 mm, MNHN IM 2009-8733, MIRIKY stn DW3239 14°30'S, 47°26'E, 230-288 m, off NW Madagascar.

Description.

Shells greyish white, H to 13.5 mm, L to 15.2 mm, T 3.8 mm, longer than high H/L = 0.91 ± 0.038 (n=8), T/L = 0.24 ± 0.018 (n=8), subovate, posterior truncate, anterior dorsal area marked by shallow double sulcus, anterior dorsal margin with elevated lamellae, umbones low, sculpture of widely spaced commarginal lamellae that are reflected ventrally, no radial sculpture. Microsculpture of fine growth increments (Fig. 11L). Lunule lanceolate, strongly asymmetric with larger part in LV. Protoconch (Fig. 11M): PI+ PII 183 µm, PII a narrow rim. Hinge (Figs 11J, K): LV with 1 thin cardinal tooth, laterals absent, RV with small, single, cardinal tooth, small anterior lateral tooth, posterior lateral teeth absent. Anterior adductor scar short, detached from pallial line for ¼ of length, posterior scar ovoid. Pallial line discontinuous in short narrow blocks. Shell interior glossy, shell margin smooth.

Distribution.

Western Indian Ocean, off Zanzibar and Madagascar from 200-825 m (Fig. 4).

Etymology.

Latin reflexa means bent or turned back, a reference to the form of the commarginal lamellae. Adjective nominative singular

Remarks.

This species was referred to Lucina inanis (Prashad) by Knudsen (1967) and the same specimens were figured and briefly discussed by Bouchet and Cosel (2008) who thought they more closely resembled species of Alucinoma . The type and other material of Lucina inanis from Indonesia and Philippines differ in shape and lack the regular, reflexed commarginal lamellae ( Glover and Taylor in press). Characters of the new species suggest a placement in Myrtina and this position is corroborated by molecular evidence that places Myrtina reflexa in the subfamily Leucosphaerinae close to species UGS -1(now recognised as a new Myrtina species) from the Philippines ( Taylor et al. 2011). Myrtina occur in offshore habitats from 30-1200 m from the Philippines and New Caledonia and are likely present in organically enriched sediments throughout the tropical Indo-West Pacific.

Myrtina reflexa differs from the genotype, Myrtina porcata , by the more widely spaced and reflexed commarginal lamellae. It is most similar to a new Myrtina species ( Glover and Taylor in press) from 200-1200 m around the Philippines but is larger and has more prominent and reflexed commarginal lamellae.