Flexopteron constantinense Merle, Pacaud, Ledon & Goret, 2024, n. sp.

Flexopteron constantinense n. sp. (Figs 20 A-D; 27M, N) urn:lsid:zoobank.org:act: E9257B15-F0B3-4134-9514-789263749385 TYPE MATERIAL. — Holotype. France • Normandy, Manche, Rauville-la-Place (Cauvin); Argiles à Corbules Formation; late Eocene (Priabonian); MNHN.F.A77760 (MNHN coll.), H: 9.2 mm (fragment of last whorl) (Figs 20C, D; 27N). Paratypes. France • 1 spm (juvenile); same as for the holotype; MNHN.F.A77761 (MNHN coll.), juvenile (Figs 20A, B; 27M) • 10 spm (juveniles); idem; MNHN.F.A90551 (MNHN coll.). ETYMOLOGY. — From the Latin adjective Constantinus in reference to the type region of the species (pagus constantinus of the GalloRoman), the Cotentin (Manche). TYPE HORIZON. — Argiles à Corbules Formation, late Eocene (Priabonian), stratigraphic data given by Cavelier (1979) and Chateauneuf (1980). TYPE LOCALITY. — France, Normandy, Manche, Rauville-la-Place (Cauvin), Cavelier (1979). DISTRIBUTION. — Normandy (France), late Eocene (Priabonian). DESCRIPTION Smooth, paucispiral protoconch of 1.5 whorls. Teleoconch probably biconic (spire broken in most adult specimen), last whorl (holotype) up to 9 mm in height, up to 7 mm in width. Moderately high spire in juveniles. Rounded to subcarinate whorls. First whorl to fourth whorl: no cord. Fifth whorl: weak P1 to P5. P1 spine poorly developed. Axial sculpture with five sublamellose varices on first whorl, seven on second whorl, eight on third and fourth whorls. Ten varices on holotype. Ovate aperture, siphonal canal short. Columellar lip smooth, adherent posteriorly. No anal sulcus, no parietal callus. Outer lip with denticles D1, D2 and D3. Shoulder sinus of P1 spine shallow. Pseudo-umbilicus narrow. Siphonal canal short, open. COMPARISONS Although the material is composed of juvenile specimens (paratypes) and a last whorl of an adult specimen (holotype), it differs clearly from all Bartonian and Priabonian species from Northern Europe. The early whorls of Flexopteron albionis (Wrigley, 1930) from Barton beds, F. subplicatilis (Wrigley, 1930) from the Bartonian of Southampton Dock and F. spinulosum (Deshayes, 1835) from the Bartonian of the Paris Basin differ from those of F. constantinense n. sp. by having a more ornamented spiral sculpture with well developed P1 to P3. Flexopteron elatior (von Koenen, 1889), found in the Bartonian of the Paris Basin and in the Priabonian of Lattorf (Germany) is another species bearing strong spiral ornamentation.