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

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

Fig. 111 View FIGURE 111

Lepidochitona charlesi View in CoL Dell’Angelo, Lesport, Cluzaud & Sosso, 2020b, p. 23, fig. 14.

Type material. Holotype: MHNBx 2020.3.6, intermediate valve, width 3.8 mm, Figs 111A–E View FIGURE 111 . Paratypes: MHNBx 2014.14.23.5, intermediate valve present in the lot deposited in the Benoist collection, labeled Lepidopleurus daubrei ; MZB 50571, topotypic intermediate valve, Figs 111F–H View FIGURE 111 .

Type locality. Gaas , Larrat ( France) .

Type stage. Oligocene (Rupelian).

Material examined. Oligocene (Rupelian): Gaas: type material plus Rupelian levels: 1 intermediate valve, width 3.2 mm ( BD 936 ); Larrat: 8 intermediate valves, maximum width 4 mm ( AC) .

Description. Head and tail valves not present.Intermediate valve broadly rectangular (W/L =1.56–1.78), rounded in anterior profile, highly elevated (H/W = 0.55–0.70), anterior margin almost straight, lateral margins slightly rounded, posterior margin slightly concave at both sides of prominent apex, lateral areas scarcely differentiated.

Tegmentum entirely covered by irregularly arranged, weak elevated, triangular to oval granules, not coalescent, diameter up to 110 μm; each granule with a more or less central megalaesthete, and up to 6 micraesthetes arranged irregularly along margin, additional micraaesthetes present between granules.

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

Remarks. The valve from the Benoist collection at MHNBx (MHNBx 2014.14.23.5), labeled Lepidopleurus daubrei de Rochebrune, 1882 , has been considered conspecific to Lepidochitona charlesi Dell’Angelo, Lesport, Cluzaud & Sosso, 2020 by Dell’Angelo et al. (2020b).

The shell characters in this species shows little variability. Only one valve ( Figs 111F–H View FIGURE 111 ) is much higher (H/W = 0.70, while all the other valves examined have H/W = 0.55–0.61) and has a more rounded to semicarinate anterior profile. The second slit in the articulamentum is smaller and near the posterior margin, not clearly visible in the holotype, but well evident in the rest of the material examined ( Fig. 111G View FIGURE 111 ).

Comparisons. Lepidochitona charlesi Dell’Angelo, Lesport, Cluzaud & Sosso, 2020 is characterized by having the tegmentum entirely covered by irregularly arranged triangular to oval granules ( Fig. 111B View FIGURE 111 ), larger than the other species of Lepidochitona from Gaas [except L. tarbelliana Dell’Angelo, Lesport, Cluzaud & Sosso, 2020]. The closest species is Lepidochitona tarbelliana , from which L. charlesi differs by the different shape of the valves (W/L = 1.56–1.78 vs. 1.82–2.26 in L. tarbelliana ), higher elevation (H/W = 0.55–0.70 vs. 0.39–0.47 in L. tarbelliana , and the triangular to oval granules, not coalescent.

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