Lepidochitona adunca

Lepidochitona adunca ( Dell’Angelo, Lesport, Cluzaud & Sosso, 2020)

Fig. 108 View FIGURE 108

Tonicella adunca View in CoL Dell’Angelo, Lesport, Cluzaud & Sosso, 2020b, p. 36, fig. 23; Sirenko & Dell’Angelo 2023, p. 278. Lepidochitona adunca ; Sirenko & Dell’Angelo 2023, p. 280.

Type material. Holotype: MHNBx 2020.5.1, tail valve, width 2 mm, Figs 108F–H View FIGURE 108 . Paratypes: MHNBx 2020.5.2, head valve, width 1.8 mm, Figs 108A–B View FIGURE 108 ; MHNBx 2020.5.3, intermediate valve, width 2.4 mm, Figs 108C–E View FIGURE 108 .

Type locality. Lariey ( France) .

Type stage. Miocene (Aquitanian).

Material examined. Lower Miocene (Aquitanian): Lariey: type material plus 12 valves ( JFL); Pouquet: 1 head valve ( JFL). Maximum width of the valves: 1.8 / 2.7 / 2.2 mm .

Description. Head valve semicircular, apex recurved. Intermediate valves broadly rectangular, width twice length (W/L = 2.00–2.25), rounded in anterior profile, moderately elevated (H/W = 0.30–0.35), anterior margin slightly convex, lateral margins rounded, posterior margin concave at both sides of prominent apex, lateral areas scarcely differentiated. Tail valve semicircular (W/L = 1.64), weakly elevated, anterior margin slightly convex, mucro subcentral, antemucronal slope almost straight, postmucronal slope concave.

Tegmentum smooth, displaying very fine microgranulation, aesthetes of same size.

Articulamentum with apophyses small and trapezoidal, extending to lateral margins in intermediate valves, slit formula 8 / 1 / 11–12, teeth inequidistant.

Remarks. Lepidochitona adunca ( Dell’Angelo, Lesport, Cluzaud & Sosso, 2020) is know only for two sites in the Aquitanian Basin (Pouquet, and Saucats) from the Miocene (Aquitanian).

This species was initially attributed to the genus Tonicella Carpenter, 1873 , and later included by Sirenko & Dell’Angelo (2023) in the genus Lepidochitona Gray, 1821 , which, since the Eocene, was widespread in the Tethys Ocean. Apparently, Tonicella first appeared in the Atlantic Ocean during the Pliocene ( Sirenko & Dell’Angelo 2023).

Comparisons. Lepidochitona adunca differs from L. lira Cherns & Schwabe, 2019 , mainly by the smooth surface (vs. lateral areas rugose in L. lira ), posterior margin tapering to a pointed apex (vs. almost straight with apex not evident in L. lira ), recurved apex in the head valve, and trapezoidal apophyses extending to lateral margins in intermediate valves.

Distribution. Lower Miocene: northeastern Atlantic (Aquitanian): Aquitaine Basin, France: Lariey, Pouquet ( Dell’Angelo et al. 2020b).