Lepidochitona canariensis ( Thiele, 1909 )

Lepidochitona canariensis ( Thiele, 1909) View in CoL

Fig. 109 View FIGURE 109

Trachydermon canariensis Thiele, 1909, p. 15 , pl. 2, figs 14–25; Bergenhayn 1931, p. 14, pl. 2, figs 57–58.

Lepidochitona canariensis View in CoL ; Kaas & Van Belle 1985b, p. 95, fig. 44, map 17; Dell’Angelo & Smriglio 1999, p. 154, pl. 51, fig. 78; Dell’Angelo et al. 2004, p. 36, pl. 3, fig. 3; Garilli et al. 2005, p. 136; Koskeridou et al. 2009, p. 316, figs 9.5–9.7; Dell’Angelo et al. 2013, p. 91, pl. 8, figs L–Q; Dell’Angelo et al. 2020b (cf.), p. 29, figs 19D–F ( non figs A–C = Lepidochitona sp. , fide this study); Dell’Angelo et al. 2021b, p. 425, figs 142–145; Dell’Angelo et al. 2022, p. 15.

Type material. Holotype ZMHU 101918 View Materials .

Type locality. Canary Islands, Tenerifa, Puerto .

Material examined. Upper Miocene: France (Messinian?): Moulin-Pochas: 1 valve ( PR, Fig. 109I View FIGURE 109 ). Lower Pliocene: Italy: Liguria: Borzoli: 3 valves ( BD 927, MZB 45757), Bussana: 1 valve ( BD 928), Genova Sestri: 2 valves ( BD 929, Figs 109J–L View FIGURE 109 ), Rio Sant’ Antonino: 2 valves ( MP, MZB 45756), Rio Torsero: 1 valve ( BD 930, Figs 109C–D View FIGURE 109 ). Pliocen e: Portugal: Vale de Freixo: 2 valves (lost during photography). Spain: Estepona: 2 valves ( BD 931); Italy: Piedmont: Vintebbio: 5 valves ( BD 932, Figs 109E–H View FIGURE 109 ); Tuscany: Poggio alla Fame: 10 valves ( BD 933, Figs 109A–B View FIGURE 109 ). Pleistocene: Italy: Calabria: Gallina: 8 valves ( BD 934). Maximum width of the valves: 2.5 / 4.8 / 1.4 mm.

Description. Head valve about three fifth of a circle, front slope straight. Intermediate valves broadly rectangular (W/L = 2.58–2.86), moderately elevated (H/W = 0.28–0.42), semicarinate in anterior profile, anterior margin concave between the apophyses, side margins rounded, posterior margin almost straight, with small but well pronounced apex, lateral areas hardly raised, though sometimes indicated by a faint diagonal fold. Tail valve about one third of a circle (W/L = 2.04–2.38), anterior margin almost straight, mucro subcentral or in anterior position, prominent, antemucronal slope almost straight, postmucronal slope slightly concave just under mucro.

Tegmentum uniformly covered with diamond-shaped granules (maximum length 60–80 µm), arranged in irregular quincunxes, tending to form converging longitudinal rows on PA. Each granule with one central megalaesthete surrounded by 10–15 micraesthetes.

Articulamentum with apophyses small, more or less triangular, teeth blunt, roughened on outside, slit formula 7–10 / 1 / 8–10, slits short, slit rays clearly visible, eaves spongy.

Remarks. The species is rather rare as a fossil, scarce reports from the French Miocene of Ligerian Basin, more common from Pliocene and rare from the Italian Pleistocene.

Dell’Angelo et al.(2020b) attributed tentatively to Lepidochitona canariensis ( Thiele, 1909) a single intermediate valve ( Fig. 154O–P View FIGURE 154 ) from the lower Miocene (Burdigalian)of the Aquitaine Basin.Despite a morphological similarity with L. canariensis , this identification is doubtful and is therefore left in open nomenclature as Lepidochitona sp. (see below, “species of problematic assignment”).

Comparisons. Lepidochitona canariensis is closest to L. caprearum ( Scacchi, 1836) , from which it differs by the head valve without radial depressions (present in L. caprearum ), the different shape of the tail valve, the sculpture with more irregular and smaller granules (more roundish in L. caprearum ).

Distribution. Upper Miocene: northeastern Atlantic: Ligerian Basin, France: Moulin Pochas ( Dell’Angelo et al. 2020b). Lower Pliocene: central Mediterranean, Italy: Liguria: Bussana, Rio S. Antonino, Rio Torsero, Sestri Ponente, Borzoli ( Sosso & Dell’Angelo 2010; Dell’Angelo et al. 2013). Pliocene: northeastern Atlantic, Mondego Basin, Portugal ( Dell’Angelo & Silva 2022). Western Mediterranean, Estepona Basin, Spain: Estepona (Dell’Angelo et al. 2004); central Mediterranean, Italy: Piedmont: Vintebbio, Tuscany: Poggio alla Fame (this study). Upper Pliocene to upper Pleistocene: central Mediterranean, Greece: Rhodes Island ( Koskeridou et al. 2009). Pleistocene: central Mediterranean, S. Italy: Gallina (this study). Recent: Atlantic Ocean: Portugal, Spain (Carmona Zalvide et al. 2000); Mauritania: Agadir Island ( Anseeuw & Verstraeten 2009), Madeira ( Van Belle 1985; Kaas 1991), Selvagens Arch. ( Segers et al. 2009), Cape Verde Arch. ( Strack 2005), Azores ( Avila & Sigwart 2013) and the Canary Islands ( Leloup 1968; Van Belle 1984; Kaas 1991; Hernández & Rolán 2011). Mediterranean Sea: Morocco: Torres de Alcalà ( Dell’Angelo & Tringali 2000).