Barbierella louisensis ( Viader, 1951 )

Taylor, John D. & Glover, Emily A., 2018, Hanging on - lucinid bivalve survivors from the Paleocene and Eocene in the western Indian Ocean (Bivalvia: Lucinidae), Zoosystema 40 (7), pp. 123-142 : 130

Barbierella louisensis ( Viader, 1951)

( Fig. 4A-W )

Lucina (Bellucina) louisensis Viader, 1951: 133 , pl. 3, fig. 6.

Barbierella scitula Oliver & Abou-Zeid, 1986: 222 , pl. 23, figs 1-4.

Barbierella louisensis – Huber 2015: 430.

TYPE MATERIAL. — Lucina (Bellucina) louisensis : 3 syntypes (Via- der mentioned 5 valves), single left valves, L 6.2 mm, H 5.2 mm; L 5.5 mm, H 4.7 mm (Viader figured shell); broken valve H 5.4 mm ( AMS C 305545) . Barbierella scitula : holotype, off Ras Budran, Gulf of Suez, Red Sea, 30 m, L 8.2 mm, H 7.4 mm ( NMW Z 1982.68.1) . Paratypes: ( NMW.Z. 1986.11.1), L 9.4 mm, H 8.7 mm; ( NHMUK 1986030), L 8.7 mm, H 7.7 mm .

TYPE LOCALITY. — Off Port Louis, Mauritius.

OTHER MATERIAL EXAMINED. — Northern Mozambique Channel: Banc de la Zélée, Expédition BENTHEDI, stn R110, lagoon with sandy bottom and dense seagrass Thalassodendron ciliatum . 12°25’6S, 46°16’2 E, 24 m, 10.IV.1977, 1 pv, co-occurs with Gibbolucina zelee n. sp. ( MNHN). Mozambique: Inhaca Island, “Nord de la Passe”, Expédition INHACA stn MD13, 26°03.1’S, 33°01.0’E, 50-53 m, 30.XI.2011, 9 v ( MNHN).

DISTRIBUTION. — Northern Red Sea, Mozambique Channel, Mozambique, Mauritius, Réunion.

DESCRIPTION

Small, L to 9.4 mm, H to 8.7 mm, longer than high. Anteriorly extended, anteriorly rounded but posteriorly truncate, anterior dorsal margin long. Umbones prominent. Sculpture of prominent, dorsally recurved, nodulose, commarginal lamellae with narrow, deep interspaces. Lobate nodules on lamellae aligned to give appearance of radial ribbing. Posterior sulcus with lower, sharper lamellae and forming a curved marginal sinus. Shallow anterior sulci present. Anterior and posterior margins of posterior sulcus with some lamellae projected into blunt spines. Microsculpture finely punctate. Protoconch (Inhaca specimen) ( Fig. 4W ): PI + PII = 190 µm, PI = 172 µm smooth, PII a narrow rim. Lunule short, deeply scooped, smooth. Ligament short, in shallow groove. Hinge teeth: right valve with single cardinal tooth, left valve with central socket, anterior cardinal possibly fused with edge of lunule; lateral teeth absent. Anterior adductor muscle scar short, detached for about 1/3 of length, posterior scar ovate. Pallial line entire. Inner shell margin coarsely dentate. Colour white.

REMARKS

This is a rare species in the western Indian Ocean and Red Sea. Despite intensive sampling ( Zuschin & Oliver 2003) there have been no other Red Sea records except that of Oliver & Abou-Zeid (1986). Around Mauritius, the species has not been recorded since Viader’s (1951) original description nor from intensive sampling around southern Madagascar (ATIMO VATAE Expédition MNHN 2010). The shell from Réunion illustrated as B. louisensis (http://vieoceane.free.fr) is a species of Notomyrtea Iredale, 1924 but the Barbierella sp. is B. louisensis . Major features of the anatomy of B. scitula were described and illustrated by Oliver & Abou-Zeid (1986). These features are common to most lucinids and include ctenidia with single demibranchs, vermiform foot, short length of posterior mantle fusion, the inhalant aperture fringed with papillae and the exhalant introvert ‘siphon’.

Figures

FIG. 4. — Barbierella louisensis (Viader,1951): A-D, Lucina (Bellucina) louisensis Viader,1951 syntypes (AMS C.305545),off Port Louis, Mauritius,L (A, B) 6.2 mm, (C) 5.5 mm, H (D) 5.4 mm. Images by A. C. Miller, Copyright:Australian Museum; E-G, Barbierella scitula Oliver & Abou-Zeid, 1986, holotype (NMW.Z.1982.68.1) exterior of right and interior of right and left valves (gold coated for SEM), off Ras Budran, Gulf of Suez, Red Sea, 30 m, L 8.2 mm, Images copyright NMW; H-K, Barbierella louisensis, Banc de la Zélée, Mozambique Channel, BENTHEDI stn 110, 24 m; H, I, exterior and interior of left valve, L 7.8 mm; J, K, interior and exterior of right valve, L 7.8 mm; L-W, Barbierella louisensis Inhaca, Mozambique, INHACA stn MD13, 50-53 m (MNHN); L, M, interior and exterior of right valve, L 6.0 mm; N, O, exterior and interior of left valve, L 5.9 mm; P, Q, interior and exterior of right valve, L 5.9 mm; R, exterior of right valve coated SEM im- age, L 6.5 mm; S, T, detail of hinge area of right and left valves; U, detail of lunule and dentition of right valve; V, detail of sculpture of R,; W, protoconch. Scale bars, S, T, 1 mm; U, V, 500 µm; W, 100 µm.