Acanthochitona mathiasi Dell'Angelo, Sosso & Taviani, 2025, sp. nov.

Acanthochitona mathiasi sp. nov. Fig. 138 Acanthochitona fascicularis (non Linnaeus); Dell’Angelo et al. 2016, p. 86, pl. 5, fig. 9. Type material. Holotype: MZB 32107, tail valve, width 7.5 mm (Figs 138A–D). Type locality. Borelli (Piedmont, Italy). Type stage. Upper Miocene (Tortonian). Etymology. We name this species after Mathias Harzhauser in recognition of his outstanding contribution to the taxonomy and biogeography of European Cenozoic Mollusca. Material examined. Upper Miocene: Italy: Borelli: type material. Diagnosis. Tail valve elliptical/polygonal, jugal area neatly separated from lateropleural area, mucro well evident in posterior position. Whole tegmentum (except JA) sculptured with densely packed, elevated, irregularly arranged roundish granules. Articulamentum particularly expanded, more than three times width of tegmentum area, apophyses very protruding. Description. Head and intermediate valves unknown. Tail valve elliptical/polygonal, with greatest diameter along longitudinal axis (WT/LT = 0.81), jugal area neatly separated from lateropleural area, mucro well evident in posterior position, antemucronal and postmucronal slopes almost straight. Whole tegmentum (except JA) sculptured with densely packed roundish granules, flattened at top, elevated, irregularly arranged. Articulamentum particularly expanded, more than three times width of tegmentum area, apophyses very protruding, completely surrounding tail valve, except for wide jugal margin, two slits. Remarks. The only valve available is strongly characterised by the reduced tegmentum and the strongly protruding apophyses, a feature not present in any other European Acanthochitona spp. The jugal area is eroded, so that its sculpture cannot be appreciated. Comparisons. The species shares the large expansion of the articulamentum with Acanthochitona mastalleri Strack, 1989, an extant species from the Red Sea, also recorded from the late Pleistocene (Dell’Angelo et al. 2020a), which differs in having such diminished tegmentum that the anterior part of the tail valve is only the jugum without lateropleural areas with granule sculpture. Distribution. Upper Miocene: Proto-Mediterranean Sea (Tortonian): Po Basin, N. Italy: Borelli (this study).