Seila quinquecarinata, Bouchard & Wesselingh & Pouwer & Landau, 2025

Bouchard, Blanche, Wesselingh, Frank P., Pouwer, Ronald & Landau, Bernard, 2025, The Gelasian gastropod fauna of Selsoif (Manche, France), Geodiversitas 47 (3), pp. 39-91 : 55

Seila quinquecarinata n. sp.

( Fig. 6C 1-C 4 , D 1-D 3 )

urn:lsid:zoobank.org:act:728DCCE3-1D4E-4A21-B87B-CD41D41CAA98

TYPE MATERIAL. — Holotype: MNHN.F.A91316 , height 8.1 mm (incomplete), width 2.7 mm, leg. AWJ . — Paratypes: paratype 1, RGM.1365312 , height 3.9 mm (incomplete), width 1.5 mm, leg. AWJ ; paratype 2, RGM.1364992 , height 4.8 mm (incomplete), leg. AWJ ; paratype 3, RGM.1365010 , height 5.5 mm (incomplete), leg. AWJ .

OTHER MATERIAL. — Maximum height 8.1 mm (incomplete), width 2.7 mm. — RGM.1365119 (26 fragments), leg. AWJ; RGM.1365015 (14 fragments), leg. ACJ; RGM.1364931 (1), leg. WG.

ETYMOLOGY. — Named reflecting the spiral sculpture consisting of five cords on later adult whorls.

TYPE LOCALITY. — Selsoif , Saint-Sauveur-le-Vicomte, Manche department, NW France.

STRATUM TYPICUS. — Gelasian, Early Pleistocene

DIAGNOSIS. — Small Seila species with paucispiral protoconch of one rounded whorl, strongly convex teleoconch whorls with five spiral cords on later adult whorls.

DISTRIBUTION. — Lower Pleistocene: Atlantic, endemic to Selsoif, NW France (this paper).

DESCRIPTION

Shell small, turritelliform. Protoconch paucispiral, consisting of one convex whorl with raised nucleus. Teleoconch of at least seven strongly convex whorls separated by moderately impressed linear suture. Sculpture on first teleoconch whorl of three elevated cords, adapical cord placed on subsutural ramp weakest, middle cord delimiting shoulder strongest, abapical cord slightly weaker than mid-cord. Abapically, upper cord strengthens, so that on third teleoconch whorl three strong primary cords, mid-cord still slightly stronger forming whorl periphery, fourth cord appears on subsutural ramp. On fourth whorl a fifth primary cord appears on subsutural ramp; later whorls with five primary spiral cords, upper two slightly weaker than lower three. Fine, elevated axial lamellae present in spiral interspaces. Last whorl short, strongly convex, with six cords above the level of the insertion of the outer lip plus weak peribasal cord; base smooth. Aperture small, rounded, outer lip simple, oblique in profile.

REMARKS

The late Neogene of NW France is proving fertile hunting ground for endemic Seila species ( Marquet 2001; Landau et al. 2018). Seila quinquecarinata n. sp. is the second Seila species endemic to the Sesoif assemblage. It is immediately separated from all its European Neogene congeners in having five spiral cords on later adult whorls. All the Seila species discussed by Marquet (2001) and Landau et al. (2018) have the more usual number of three spiral cords on all adult whorls. It is also separated from all the present-day Atlantic species discussed by Rolán & Fernandes (1990) that have multispiral protoconchs. It is also unusual in having strongly convex whorls. Most Seila species have relatively flat-sided whorls. The shell is somewhat reminiscent of a Mathilda species, but these are immediately separated by their heterostrophic protoconch.

Figures

FIG. 6. — Gastropods from Selsoif.All illustrated specimens are collected from the Sablière du Grand Marais,Selsoif,France and come from the Early Pleistocene Saint- Nicolas de Pierrepont Formation (continuation): A, Monophorus indet., RGM.1365279, leg AWJ, H = 17.19 mm; B, Seila selsoifensis Marquet 2001, RGM.1365180, leg ACJ, H = 3.4 mm;C, Seila quinquecarinata n. sp. (holotype), MNHN.F.A91316,leg AWJ, H = 4.2 mm;D, Seila quinquecarinata n. sp. (paratype), RGM.1365312, leg AWJ, H = 3.9 mm; E, Cerithiopsis sp., RGM.1365306, leg ACJ, H = 3.5 mm; F, Cerithiopsis indet., RGM.1365309, leg ACJ, H = 2.8 mm; G, Cerithiopsis indet., RGM.1365212, leg ACJ, H = 2.15 mm. Scale bars:A1-A3, 5 mm; B1-B3, C1-C3, D1, D2, E1-E3, G1-G3, 1 mm; B4, 200 μm; F1-F3, C4, D3, 500 μm.

FIG. 1. — Simplified geological map of the Normandy region (after Dugué et al. 2000 and Pareyn 1987) showing the location of Selsoif:1, Precambrian-Palaeozoic basement; 2, Permo-Mesozoic Paris Basin fill; 3, Neogene-Quaternary subbasins.

FIG. 4. — Gastropods from Selsoif. All illustrated specimens are collected from the Sablière du Grand Marais,Selsoif,France and come from the Early Pleistocene Saint-Nicolas de Pierrepont Formation:A, Patella rustica Linnaeus,1758,RGM.1365190,leg.AWJ,H = 7.6 mm; B, Patella vulgata Linnaeus,1758,RGM.1310830, leg. AWJ, L = 15.14 mm; C, Tectura virginea (Müller, 1776), RGM.1365189, leg. ACJ, L = 4.9 mm; D, Diodora graeca (Defrance, 1820), RGM.1365174, leg. AWJ, L = 15.04 mm; E, Emarginula fissura (Linnaeus, 1758), RGM.1365175, leg. WG, L = 4.6 mm; F, Jujubinus exasperatus (Pennant, 1777), RGM.1365178, leg ACJ, L = 3.5 mm; G, Jujubinus montagui (Wood, 1828), RGM.1365179, leg. AWJ, L = 4.3 mm; H, Steromphala cineraria (Linnaeus, 1758), RGM.1365177, leg. ACJ, L = 8.4 mm; I, Steromphala cineraria (Linnaeus, 1758), RGM.1310831, leg. AWJ, L = 3.6 mm; J, Steromphala tumida (Montagu, 1803), RGM.1310832, leg. SM, L = 4.6 mm; K, Calliostoma normanensis n. sp. (holotype), MNHN.F.A91315, leg. AWJ, L = 8 mm. Scale bars: A, C, D, H, K, 2mm; B, 5 mm; E-G, I, J, 1 mm.

FIG. 3. — Simplified biographic map of South-West of Europe (after Landau et al. 2011).