Retrolucina voorhoevei ( Deshayes, 1857 ) Taylor & Glover, 2018

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 : 135-136

Retrolucina voorhoevei ( Deshayes, 1857) n. comb.

( Figs 6A-H ; 7A, B )

Lucina voorhoevei Deshayes, 1857: 106 , pl. 2, fig, 1. Holotype not located. Dance (1986: 154) lists 1872 sales catalogue of J. Voorhoeve collection where the holotype of Lucina voorhoevei was sold to H. C. R. van Lannep and then later listed in the 1876 sale catalogue of his collection ( Jutting 1939) but its subsequent whereabouts is unknown.

Lucina mirabilis Dunker, 1865: 77 , pl. 26, figs 7-9.

Gibbolucina (Eomiltha) voorhoevei – Chavan 1938: 93. — Kilburn 1974: 343, figs 6, 7.

Eomiltha voorhoevei – Oliver 1995: 236, fig. 1029. — Huber 2015:

106, 458.

TYPE LOCALITY. — Not given in original but cited as Mozambique by Heukolom 1866.

MATERIAL EXAMINED. — Algoa Bay (unlikely) ( NHMUK 20170373) ; Mozambique ( USNM 628930) ; Mozambique ( ANSP 234103) ; Mozambique: Mucoque, near Vilanculos ( MNHN) .

DISTRIBUTION. — Mozambique: Mucoque (MNHN), Inhassoro, Mucoque and Bazaruto Island ( Kilburn 1974); Madagascar: NW Madagascar (ANSP); Kenya: Ukunda ( Huber 2015); Oman: Masirah ( Oliver 1995), Muscat (NMW BV6059).

HABITAT. — No live collected specimens are known. Most records are beach collected and the species is assumed to live subtidally but Huber (2015) records dead shells at 5 m depth in southern Kenya.

DESCRIPTION

Shell large, L to 80 mm, ovoid, tapering to anterior and posterior, thin shelled, relatively flat T 8.3 mm single valve. Umbones small, low. Posterior dorsal area faintly delineated by shallow sulcus. Sculpture generally smooth with irregular growth lines. Lunule small, narrow, triangular. Ligament short, set in shallow groove. Hinge line thin, RV with two cardinal teeth the posterior bifurcate, anterior tooth smaller, LV with two cardinal teeth, anteriormost bifurcate; lateral teeth absent in both valves. Anterior adductor muscle scar long, narrow, curved, extends ventrally to past mid-line of shell, detached and widely separated from pallial line for nearly all of length. Posterior adductor scar reniform. Pallial line narrow, entire. Pallial blood vessel scar visible, terminating ventrally at lower part of anterior adductor scar. Shell interior with fine radial ridges and sometimes exposed organic layers. Shell outside pallial line glossy, margin smooth.

REMARKS

Among living Lucinidae Retrolucina voorhoevei n. comb. has an unusual, elongate, laterally compressed shell shape that is only matched by some deep water taxa such as Gloverina and Elliptiolucina ( Cosel & Bouchet, 2008) or Jorgenia (Tay - lor & Glover, 2009) but these have short anterior adductor muscle scars and molecular results show they belong in the Myrteinae ( Taylor et al. 2014, 2016). By contrast, although details of habitat are lacking, the presence of dead shells on beaches suggests that R. voorhoevei n. comb. is a shallow subtidal species. The Eocene congener, R. defrancei , was also a shallow water species recorded by Courville et al. (2012) from the Paris Basin at Damery (Lutetian), in beds associated with cerithiid and potamidid gastropods.

Figures

FIG. 6. — A-H, Retrolucina voorhoevei n. comb.(Deshayes,1857),Recent;and I-N, R.defrancei (Deshayes,1857),Eocene;A-C, exterior of right and interiors of right and left valves, Mozambique (ANSP 234103),L 70 mm; D, E, exterior and interior of left valve, Mozambique (USNM 628930), L 78 mm; F, dorsal view (NHMUK 20170373), L 78 mm; G, H, details of hinge of right and left valves (NHMUK 20170373),scale bar,10 mm; I, J, Retrolucina defrancei (Deshayes,1857) exterior and interior of left valve Eocene,Lutetian,Chaumont-en-Vexin,Oise,France (MNHN.F.J07396), L 35 mm;K, L, Retrolucina defrancei (Deshayes,1857),Eocene,Lutetian,Chaussy,Seine et Oise, France, (RBINS IG10591), L 71 mm;M, N, Retrolucina defrancei (Deshayes,1857), Eocene,Lutetian,Parnes,France,Deshayes collection (NHMUK 33283a),L 50.4 mm.

FIG. 7. — Eomiltha Cossmann,1912 and Retrolucina n. gen., outline drawings of interiors of valves:A, Retrolucina voorhoevei n. comb.(Deshayes,1857), Recent, Mozambique (USNM 628930); B, Retrolucina voorheoevi Recent, Mozambique (ANSP 234103); C, Retrolucina defrancei (Deshayes, 1857) Eocene, Lutetian, Chaumont-en-Vexin, France (MNHN.F.J07396); D, Retrolucina defrancei (Deshayes, 1857) Eocene. Lutetian, Parnes (NHMUK 33283a); E, F, Eomiltha contorta (Defrance,1825) Paleocene,Thanetian,Abbecourt (MNHN);G, ‘Eomiltha’ pandata (Conrad,1833) Eocene,Claiborne Formation,USA (NHMUK L 4402).Not to scale.