Lepidochitona vancuycki, Dell'Angelo, Lesport, Cluzaud & Sosso, 2020

Lepidochitona vancuycki View in CoL Dell’Angelo, Lesport, Cluzaud & Sosso, 2020

Fig. 123 View FIGURE 123

Lepidochitona vancuycki View in CoL Dell’Angelo, Lesport, Cluzaud & Sosso, 2020b, p. 24, fig. 15.

Type material. Holotype MHNBx 2020.3.7, an intermediate valve, width 2.9 mm, Figs 123A–D View FIGURE 123 .

Type locality. Gaas , Larrat ( France) .

Type stage. Oligocene (Rupelian).

Material examined. Oligocene (Rupelian): Gaas (Larrat): type material plus 1 intermediate valve, width 3.5 mm ( JCV) .

Description. Head and tail valves not present. Intermediate valve rectangular (W/L = 1.68), rounded in anterior profile, highly elevated (H/W = 0.47–0.56), anterior margin weakly sinuose, lateral margins slightly rounded, posterior margin almost straight at both sides of poorly developed apex, lateral areas not raised, but separated from central area by a diagonal fold.

Tegmentum entirely covered by irregularly arranged, weak elevated, roundish granules, not coalescent, diameter up to 100 μm; each granule bearing a subcentral megalaesthete, and up to 6 micraesthetes arranged irregularly along margin, additional micraesthetes randomly placed between granules.

Articulamentum with rounded apophyses, slit formula two slits for each side, slit rays visible, eaves spongy.

Remarks. This species is characterized by the tegmentum entirely covered by roundish granules ( Fig. 123D View FIGURE 123 ), the “enveloping” valve with a characteristic rounded and high anterior profile ( Fig. 123C View FIGURE 123 ), and an almost straight posterior margin with a small apex ( Fig. 123A View FIGURE 123 ).

A second lower intermediate valve (H/W = 0.47, see Dell’Angelo et al. 2020b: fig. 15.E–F) has a different shape (W/L = 1.95), but the sculpture and the posterior straight margin with the small apex are similar, and has been considered falling within the range of variability of L. vancuycki Dell’Angelo, Lesport, Cluzaud & Sosso, 2020.

Comparisons. The closest species is Lepidochitona charlesi Dell’Angelo, Lesport, Cluzaud & Sosso, 2020, from which L. vancuycki Dell’Angelo, Lesport, Cluzaud & Sosso, 2020 differs by the almost straight posterior margin with a small apex (vs. slightly concave at both sides of the prominent apex in L. charlesi ), LA not raised, but separated from CA by a diagonal fold (vs. scarcely differentiated in L. charlesi ), and the smaller roundish granules (up to 100 μm, vs. triangular-oval up to 110 μm diameter in L. charlesi ).

Distribution. Lower Oligocene: northeastern Atlantic (Rupelian): Aquitaine Basin, France: Gaas ( Dell’Angelo et al. 2020b).