Stenosemus rossoae, Dell’Angelo & Sosso & Taviani, 2025

Stenosemus rossoae sp. nov.

Fig. 79 View FIGURE 79

Type material. Holotype: MSNG 62656 View Materials , intermediate valve, width 7.7 mm ( Figs 79A–D View FIGURE 79 ) . Paratype 1: MSNG 62657 View Materials , intermediate valve, width 7.5 mm ( Figs 79E–H View FIGURE 79 ) .

Type locality. Pezzo ( Calabria, Italy) .

Type stage. Upper Pleistocene .

Etymology. The species is named after Antonietta Rosso (University of Catania) in recognition of her many paleontological and biological contributions on Mediterranean Cenozoic to Recent marine invertebrates.

Material examined. Upper Pleistocene : Italy: Pezzo: type material .

Diagnosis. Intermediate valve broadly rectangular, carinate in anterior profile, elevated, apex small, LA delimited from CA by diagonal fold. Tegmentum smooth and glossy, with well marked concentric growth lines in CA, continuing across LA. Articulamentum well developed, with apophyses connected across shallow sinus by short jugal plate, insertion lamina with a single slit.

Description. Head and tail valves unknown. Intermediate valve broadly rectangular (W/L = 2.25), carinate in anterior profile, elevated (H/W = 0.48), anterior margin almost straight or slightly convex, side margins almost straight, posterior margin weakly concave at both sides of small apex, lateral areas slightly raised, delimited from central area by diagonal fold.

Tegmentum smooth and glossy to naked eye. CA with several well marked concentric growth lines, continuing, though less strongly, across LA.

Articulamentum well developed, with apophyses rounded, connected across shallow sinus by a short, straight jugal plate, faintly notched at sides, insertion plates long with a slit, slit rays weakly indicated, teeth sharp, slightly rugose on outside, eaves narrow.

Remarks. The fossil record of Stenosemus rossoae sp. nov. is limited to the upper Pleistocene of Italy. Two intermediate valves are present in the material studied, in good condition even if a little abraded.

The generic attribution is difficult, the intermediate valves with a jugal plate separated from apophyses by small notches are typical of the genus Lepidozona Pilsbry, 1892 , which, however, includes species with a tegmentum sculpture characterized by longitudinal riblets/radial rows of pustules ( Sirenko 2021b), not smooth or microgranulose. Other genera show the apophyses connected across the jugal portion, but all these have characteristics not agreeing with the material here studied, e.g., Callochiton Gray, 1847 (with a finely granulose sculpture, eaves spongy, extrapigmentary eyes present), Connexochiton Kaas, 1979 (of small size with a granulose sculpture), Stenosemus von Midendorff, 1847 (microgranulose). We provisionally attribute the material studied to Stenosemus , pending further material.

The valve’s characters are distinctive and well defined, and for these reasons, and also considering the rare records of this genus as a fossil, we have described these two intermediate valves as a new species.

Comparisons. Stenosemus rossoae sp. nov. is superficially similar to the living arctic-boreal species Stenosemus albus ( Linnaeus, 1767) , also reported from the Pleistocene of northeastern Atlantic ( Antevs 1917, 1928; Feyling-Hanssen 1955), from which it differs by the smooth tegmentum (uniformly microgranulose in S. albus ), LA delimited from CA by a diagonal fold (not present in S. albus ), the greater dimensions of the valves.

Distribution. Upper Pleistocene: central Mediterranean, S. Italy: Pezzo (this study).