Leptochiton freiwaldi, Dell'Angelo, Sosso & Taviani, 2024

Leptochiton freiwaldi View in CoL Dell’Angelo, Sosso & Taviani, 2024

Fig. 15 View FIGURE 15

Lepidopleurus ( Leptochiton) sarsi (non Leptochiton sarsi Kaas, 1981 View in CoL ); Dell’Angelo & Giusti 2000, p. 54, figs 5–10. Leptochiton freiwaldi View in CoL Dell’Angelo, Sosso & Taviani, 2024, p. 196, fig. 2.

Type material. Holotype MZUB 60348 View Materials , intermediate valve, width 3.5 mm ( Figs 15A–D View FIGURE 15 ) . Paratype 1: MZUB 60349 View Materials , head valve, width 2.1 mm ( Figs 15E–F View FIGURE 15 ) ; Paratype 2: MZUB 60350 View Materials tail valve, width 2.2 mm ; Paratype 3: MNHN-IM-2022-2408, intermediate valve, width 3 mm; Paratype 4: MNHN-IM-2022-2409, tail valve, width 2.7 mm ( Figs 15G–H View FIGURE 15 ); Paratype 5: SMF 366408 About SMF , intermediate valve, width 2.9 mm ; Paratype 6: SMF 366409 About SMF , tail valve, width 2.7 mm

Type locality. Capraia Island-Capo Corso, sediments -350/ 500 m by fishermen.

Type stage. Pleistocene, presumably last glacial.

Material examined. Pleistocene, presumably last glacial: Italy: Tuscany: Capraia Island-Capo Corso - 350/ 500 m: type material plus 100+ valves ( BD 248 ). Maximum width of the valves: 2.7 / 3.5 / 3.0 mm .

Description. Head valve semicircular,posterior margin widely V-shaped.Intermediate valves broadly rectangular (W/L = 2.43–2.85), rounded in anterior profile, elevated (H/W = 0.44–0.51), anterior margin almost straight, side margins rounded, posterior margin straight, apex not evident, lateral areas not raised with faint concentric lines of growth. Tail valve semicircular, elevated, anterior margin slightly convex, mucro subcentral, not prominent, antemucronal slope convex, postmucronal slope slightly concave.

Tegmentum rough, space between striae of granules very reduced. HV, LA, PMA sculptured with small elliptical granules (up to 40 µm) moderately raised, with 2–3 stems in apical part, randomly arranged, faint concentric lines of growth in LA, more evident in HV, PMA. CA, AMA sculptured with granules roundish and more compact (up to 55–60 µm) arranged in longitudinal series (CA 80, AMA 60), with a regular quincuncial pattern displayed by granules of neighboring rows. Each granule with a variable number of aesthetes, up to 6 in CA and AMA, and 3 aesthetes lined up along diameter in HV, LA and PMA, all aesthetes of same size.

Articulamentum without insertion laminae, weakly developed, apophyses small, triangular, wide apart in intermediate valves, trapezoid in tail valve.

Remarks. This material studied by Dell’Angelo & Giusti (2000), has been attributed to Leptochiton sarsi Kaas, 1981 (see below). Leptochiton freiwaldi Dell’Angelo, Sosso & Taviani, 2024 is presently known from submerged assemblages of putative glacial Pleistocene age trawled offshore Capraia Island and Capo Corso in the Tyrrhenian Sea at a depth of 350/ 500 m.

Comparisons. Leptochiton freiwaldi differs from Leptochiton sarsi mainly by the sculpture, with longitudinal striae of granules in CA and AMA more numerous and much closer, unlike L. sarsi , which shows tegmentum rough, and space between striae of granules large. Also the shape of the intermediate valves is different, with valves about twice as wide (W/L = 1.90–2.12) in L. sarsi , more elongated (W/L = 2.43–2.85) in L. freiwaldi .

Distribution. Pleistocene: central Mediterranean, Italy: Capraia Island-Capo Corso ( Dell’Angelo & Giusti 2000; Dell’Angelo et al. 2024; this study).