Leptochiton prudenzae, Dell’Angelo & Sosso & Taviani, 2025

Leptochiton prudenzae sp. nov.

Fig. 19 View FIGURE 19

Lepidopleurus ( Leptochiton) cimicoides [non Leptochiton cimicoides ( Monterosato, 1879) View in CoL ]; Dell’Angelo & Palazzi 1989, p. 64, pls 14–15; Dell’Angelo & Forli 1995a, p. 224; Dell’Angelo & Smriglio 1999, p. 58 (only as far as “fossil findings”); Dell’Angelo et al. 2001a, p. 147, fig. 6; Garilli et al. 2005, p. 129, pl. 1, figs 3–10.

Leptochiton cimicoides View in CoL [non Leptochiton cimicoides ( Monterosato, 1879) View in CoL ]; Koskeridou et al. 2009, p. 309, figs 7.4–7.8.

Type material. Holotype: MSNG 62630 View Materials , intermediate valve, width 2.4 mm ( Figs 19E–H View FIGURE 19 ) . Paratype 1: MSNG 62631 View Materials , head valve, width 1.5 mm ( Figs 19A–B View FIGURE 19 ) . Paratype 2: MSNG 62632 View Materials , tail valve, width 1.4 mm ( Figs 19K– L View FIGURE 19 ) .

Type locality. Poggio alla Fame ( Tuscany, Italy) .

Type stage. Pliocene.

Etymology. The name honors Micaela Prudenza ( Italy), for her contribution to the study and research of fossils from the Pliocene of Liguria and Tuscany.

Material examined. Pliocene: Italy: Tuscany: Poggio alla Fame : type material plus 3 valves ( BD 383 ); Sicily: Trappeto: 1 valve ( BD 384 ). Pleistocene : Italy: Tuscany: Riparbella : 2 valves ( BD 385 ); Puglia: Gallipoli: 1 valve (PC); Calabria: Pecoraro: 1 valve ( BD 386 ); Sicily: Selinunte, Casa Parrino: 4 valves ( BD 387 , Figs 19I–J View FIGURE 19 ) . Greece: Kyllini : 5 valves ( BD 388 , Figs 19C–D View FIGURE 19 , DGUP). Maximum width of the valves: 1.5 / 2.4 / 1.4 mm .

Diagnosis. Head valve semicircular, intermediate valves broadly rectangular, rounded, moderately elevated, apex inconspicuous, tail valve semicircular, mucro subcentral, not prominent. Tegmentum rough, sculptured with well raised, distinctly separated granules, elliptical and irregularly arranged in HV, LA, PMA, fungiform with 2–3 varices, arranged in longitudinal series in CA, AMA, each granule with 4–6 aesthetes irregularly disposed in CA and AMA, all same size.

Description. Head valve semicircular, posterior margin widely V-shaped, slope straight. Intermediate valves broadly rectangular, elongated (W/L = 2.36–3.40), rounded in anterior profile, moderately elevated (H/W = 0.33– 0.37), anterior margin stright, side margins rounded, posterior margin straight, apex inconspicuous, lateral areas hardly or not raised. Tail valve semicircular, anterior margin almost straight or slightly convex, mucro not prominent, in subcentral position, antemucronal slope slightly convex, postmucronal slope slightly concave.

Tegmentum rough. HV, LA and PMA sculptured with well raised, distinctly separated elliptical granules, irregularly arranged, close set and forming concentric lines. CA and AMA sculptured with distinctly separated fungiform granules, with a roundish body (up to 38 µm) extended with 2–3 longitudinal varices, more widely spaced and arranged in longitudinal series (CA 50–55, AMA 40–43), less parallel and slightly divergent in AMA, with a regular quincuncial pattern displayed by granules of neighboring rows. Each granule with 4–6 aesthetes irregularly disposed in CA and AMA, all aesthetes of same size.

Articulamentum without insertion laminae, with apophyses small, sharply triangular, widely separated.

Remarks. Much of the fossil material studied had already been reported in previous publications, and attributed to Leptochiton cimicoides ( Monterosato, 1879) , the least known of the four species described by Monterosato in the Mediterranean Sea. However, some differences compared to living specimens of L. cimicoides had already been highlighted, e.g., for the material from Kyllini’s Pleistocene [ Garilli et al. 2005: 130 “ The valves found agree well with the characteristics of the species, except for the number of longitudinal series of granules in central areas of intermediate valves, about 50 ( in our valves) vs. 30 ( as reported by Dell’Angelo & Smriglio, 1999)”], but interpreted as intraspecific variation by the authors. The recent discovery of abundant material from the Pliocene of Poggio alla Fame ( Tuscany, Italy) made it possible to better evaluate these differences and to attribute all the fossil material to a new species; in our opinion, L. cimicoides is at present only known as a living species in the Mediterranean Sea and is not included in the present study.

The fossil record of Leptochiton prudenzae sp. nov. refers to the Pliocene (Poggio alla Fame, Trappeto) and Pleistocene of Italy (Gallipoli, Pecoraro, Riparbella, Selinunte) and Greece (Kyllini, Rhodes).

Comparisons. The closest species is Leptochiton cimicoides ( Monterosato, 1879) , from which L. prudenzae sp. nov. differs mainly by the different number of longitudinal series of granules in central and antemucronal areas (50–55 vs. 30), the space between the striae of granules narrower, the subcentral mucro in the tail valve (in posterior position in L. cimicoides ).

Distribution. Pliocene: central Mediterranean, Italy: Poggio alla Fame (this study), Trappeto ( Dell’Angelo & Palazzi 1989). Upper Pliocene to upper Pleistocene: central Mediterranean, Greece: Rhodes ( Koskeridou et al. 2009). Pleistocene: central Mediterranean, Italy: Gallipoli, Pecoraro, Riparbella, Selinunte ( Dell’Angelo & Palazzi 1989; Dell’Angelo & Forli 1995a; this study), Greece: Kyllini ( Garilli et al. 2005).