Dermomurex (Gracilimurex) ligerianus Merle, Pacaud, Ledon & Goret, 2024, n. sp.

Dermomurex (Gracilimurex) ligerianus n. sp. (Figs 4 E-H; 25G, H) urn:lsid:zoobank.org:act: 5FD68C63-4422-4392-B888-8EFF1FB885FC Dermomurex (Gracilimurex) sp. – Merle et al. 2011: pl. 173, fig. 1-2. TYPE MATERIAL. — Holotype. France • Loire Basin, Loir-et-Cher, Pontlevoy; Faluns du Blésois (mammal biozone MN5b); Middle Miocene (base of the Langhian); MNHN.F.A33456 (Dollfus coll.) figured specimen in Merle et al. (2011: pl. 173, fig. 1a-b), H: 8 mm (Figs 4E, F; 25G). Paratype. France • 1 spm; same as for the holotype; MNHN.F.A33457 (Dollfus coll.) figured specimen inMerle et al. (2011: pl. 173, fig. 2a, b) (Figs 4G, H; 25H). ETYMOLOGY. — From the Latin adjective ligerianus meaning Loire. TYPE HORIZON. — Faluns du Blésois (mammal biozone MN5b), see Ginsburg (2000), Middle Miocene (base of the Langhian). TYPE LOCALITY. — France, Loire Basin, Loir-et-Cher, Pontlevoy (see Macaire et al. 2020). DISTRIBUTION. — Only known from the type locality. DESCRIPTION Bulbous protoconch of 1.5 whorls. Teleoconch of up to 8-9 mm in height, up to 4 mm in width, composed of five elongated whorls. Spire high, weakly convex whorls. Last whorl up to 67% of total height. Apical angle 45°. Spiral sculpture with moderately marked primary cords. First to second whorl: no cord. Third whorl: appearance of P2 on base of whorl. Fourth whorl: appearance of IP and P1 (weak), presence of P2 and P3. Fifth whorl: IP, P1 to P5 on convex part of whorl, siphonal canal smooth. From first to second whorl, six lamellose protovarices extending between sutures. On third whorl, 6-7 protovarices. From fourth to fifth whorl, two thickened varices placed at periphery, 180° to each other, with two intervarices intercalated. Bivaricate morphology giving shell laterally compressed appearance. No cord spine, but only flat nodules at intersection between axial sculpture and major cords (P1 to P5). Aperture ovate, up 35% of diameter, up to 67% of height of last whorl (including siphonal canal). Columellar lip smooth poorly erect anteriorly. Outer lip with very weak internal denticles. Series of internal denticles including ID, D1 to D4. D5 and D6 not developed. Pseudo-umbilicus narrow. Siphonal canal up to 35% of apertural lenght. Remains of intritacalx near varices. COMPARISONS All other members of the subgenera of Dermomurex [Dermomurex (s.s.), Takia Kuroda, 1953 and Viator E. H. Vokes, 1974] are characterized by a series of internal denticles containing ID, D1 to D5 or D6, whilst D5 and D6 are missing in the two known species of this subgenus: D. (Gracilimurex) bakeri (Hertlein & Strong, 1951), Recent, Eastern Pacific (Gulf of California) and D. (G.) elisabethae (McGinty, 1940), Pleistocene to Recent, Western Atlantic (Florida, Mexico). Nevertheless, only D. (Gracilimurex) ligerianus n. sp. bears a poorly developed D5, but this character state, restricted in this old species of D. (Gracilimurex), could be interpreted as the retention of the primitive state, the derived state being the loss of this denticle. The bivaricate morphology found in D. (Gracilimurex) is unique in Dermomurex and can be compared to Aspella. However, it appears early during ontogeny in Aspella, whereas it appears later (on the penultimate or the last whorl) in D. (Gracilimurex). According to Vokes (1992: 72), the shell ornamentation of D. (Gracilimurex) is more closely akin to that of Dermomurex (s.s.), especially the group of the type species. The oldest record of D. (Gracilimurex) was D. (Gracilimurex) elisabethae, found in the Pleistocene (Calabrian, Bermont Formation) of Florida. Therefore, this new species from the Middle Miocene of Loire Basin predates the previous oldest record by 12 million years and expand the geographic range of the subgenus to the Eastern Atlantic.