Leptochiton antondohrni Taviani, Sosso & Dell’Angelo, 2023

Leptochiton antondohrni Taviani, Sosso & Dell’Angelo, 2023 View in CoL

Fig. 11 View FIGURE 11

Leptochiton antondohrni Taviani, Sosso & Dell’Angelo, 2023, p. 5 View in CoL , fig. 3.

Type material. Holotype MZUB 60418 View Materials , intermediate valve, width 3.4 mm, Figs 11A–D View FIGURE 11 . Paratypes: MZUB 60419 View Materials intermediate valve, width 2.9 mm ; MZUB 60420 View Materials , tail valve, width 3.1 mm, Figs 11I–L View FIGURE 11 .

Type locality. Southwestern Adriatic Sea , Apulian margin, off Bari ( Italy), cruise SE06-50 .

Type stage. Upper Pleistocene submerged deposits, probably late glacial epoch .

Material examined. Type material, plus: SE06-10: 1 valve; SE06-35: 4 valves; SE06-40: 3 valves, Figs 11EH View FIGURE 11 ; SE06-48: 2 valves; SE06-50: 55 valves. Maximum width of the valves: -- / 3.4 / 3.1 mm.

Description. Head valve unknown. Intermediate valves broadly rectangular (W/L = 1.45–2.03), rounded in anterior profile, elevated (H/W = 0.50–0.66), anterior margin straight, side margins rounded, posterior margin straight, apex inconspicuous, lateral areas hardly or not raised. Tail valve semicircular (W/L = 1.48–1.61), anterior margin almost straight or slightly convex, mucro not prominent, in slightly anterior position, antemucronal slope slightly convex, postmucronal slope almost straight.

Tegmentum rough, space between striae of granules reduced. LA and PMA with granules more rectangular, randomly disposed along concentric lines, with numerous and well-marked growth lines; granules with a maximum width up to 60 µm and presence of 3–4 aesthetes more or less aligned, with pores of same width. CA and AMA with well raised, rather thick but distinctly separated roundish to oval granules, extended with 2–3 small longitudinal varices, forming 50–55 longitudinal series with a regular quincuncial pattern displayed by granules of neighboring rows; granules with a maximum width up to 70 µm and the presence of one subcentral aesthete and up to 6 aesthetes irregularly disposed, with pores of same width.

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

Remarks. The fossil record of Leptochiton antondohrni Taviani, Sosso & Dell’Angelo, 2023 refers to the late Pleistocene (presumably last glacial) of the Adriatic Sea, although we cannot completely exclude that is still alive in the Mediterranean Sea ( Taviani et al. 2023). The material studied is quite well preserved, and the intermediate valves show some variability. Two types of intermediate valves are detectable, some higher ( Figs 11A–D, H View FIGURE 11 /W = 0.66) and slightly larger (W/L = 1.45–1.60), others a little less high ( Figs 11E–H, H View FIGURE 11 /W = 0.50–0.55) and a little smaller (W/L = 1.91–2.03). The structure of the granules also shows slight differences, the granules in CA are more oval and up to 70 µm in size in the higher valves, more rounded and slightly smaller up to 60 µm in the lower ones.

Comparisons. Leptochiton antondohrni differs from L. prudenzae sp. nov. by the valves slightly larger, the intermediate valves more elevated (W/L = 0.50–0.66 vs. 0.33–0.37 in L. prudenzae ), and the larger granules (up to 60–70 µm vs. 38 µm in L. prudenzae ).

Distribution. Pleistocene, presumably last glacial: central Mediterranean, Italy: Adriatic Sea, offshore Bari (this study).