Beauvoisina carinata, Kiel & Campbell & Gaillard, 2010

Kiel, Steffen, Campbell, Kathleen A. & Gaillard, Christian, 2010, New and little known mollusks from ancient chemosynthetic environments, Zootaxa 2390 (1), pp. 26-48 : 41-42

Beauvoisina carinata sp. nov.

( Fig 10 )

1985 large bivalves, Gaillard et al., pl. 1, fig. 7.

1990 Lucinacea , Rolin et al., figs. 5, 6.

1992 Lucinid bivalve, Gaillard et al., fig. 7a.

Diagnosis: As for the genus.

Holotype: FSL 286 459, L = 42 mm, H = 34 mm, W = 22 mm; illustrated on Figs. 10A, J .

Paratypes: The figured specimens FSL 286 460 – 286 463.

Type locality: Seep deposits at Beauvoisin, Drôme, France, 44°18’N, 5°12’E; Late Jurassic, Oxfordian .

Material: The type material and numerous additional specimens from the late Jurassic seep carbonates at Beauvoisin, southeastern France, deposited in the FSL .

Etymology: For its carinate lunule.

Remarks: Beauvoisina carinata is the earliest record of a lucinid from a methane seep. Shells larger than ca. 50 mm are usually crushed. The adductor muscle scars are extremely weak: although several wellpreserved internal molds were available, neither the scars nor the pallial line could be detected (see figs. 10H, I, K, L). In this respect this species resembles a similarly shaped lucinid from the Early Cretaceous (Hauterivian) Crimean methane seep site, which also has very weak muscle attachment scars ( Kiel and Peckmann 2008). The Crimean species differs by lacking the elongate nymph of the Beauvoisin species. The hinge of Beauvoisina carinata differs from that of the Late Cretaceous North American Nymphalucina occidentalis Morton, 1842 by its much narrower nymph; further, N. occidentalis has a small cardinal tooth pointing posteriorly, that is lacking in Beauvoisina carinata ( Speden 1970) . The large, mid-Cretaceous lucinid Ezolucina inflata ( Kanie and Nishida, 2000) has a much higher umbo than B. carinata and a more angular shape, resembling that of vesicomyids rather than oval shape of B. carinata (see Amano et al. 2008). Another large, seep-related lucinid with late Mesozoic members is Nipponothracia , which differs from B. carinata by its edentulous hinge (Kanie and Sakai 1997; Kiel et al. 2008). Along with the tall gastropod that we describe as Humptulipsia macsotayi herein, Thieuloy (1972) reported a large bivalve from the early Cretaceous seeps at Rottier, southeastern France. This bivalve was identified (but not figured) by Macsotay (1980) as the lucinid Pseudomiltha aff. germani. The published figures of this species are insufficient for identification and our own sampling at this site revealed only fragmentary material. However, Thieuloy’s (1972) image shows a specimen with radial sculpture, which is not seen in B. carinata .

Figures

FIGURE 10. The lucinid Beauvoisina carinata gen. et sp. nov., from the late Jurassic seep carbonates at Beauvoisin, southeastern France. A. Dorsal view of the holotype (FSL 286 459) showing the lunular ridge. B. Another moderately sized specimen in dorsal view (FSL 286 460). C-G. Rubber cast of a small specimen with partially preserved hinge (FSL 286 461). H, I. Internal mold of elongate-oval specimen, showing radial striations and commarginal incisions (FSL 286 462). J. Lateral view on the holotype. K, L. Internal mold of oval specimen (FSL 286 463).