Acirsa koskeridouae, Harzhauser & Landau, 2025

Acirsa koskeridouae sp. nov.

Figs 6C View FIGURE 6 1 –C View FIGURE 1 2 View FIGURE 2 , 7F View FIGURE 7

Type material. Holotype, NHMW 1860 View Materials /0001/0289, SL: 14.5 mm, MD: 4.9 mm, Steinebrunn ( Austria), Figs 6E View FIGURE 6 1 – E View FIGURE 1 2 View FIGURE 2 , 7F View FIGURE 7

Type locality. Steinebrunn ( Austria), Vienna Basin .

Type stratum. Silt sand of the Baden Formation.

Age. Middle Miocene, Badenian (Langhian).

Etymology. In honor of Efterpi Koskeridou (National and Kapodistrian University of Athens, Greece), in recognition of her contributions to Mediterranean paleontology.

Diagnosis. Medium-sized, moderately slender, conical shell with weakly convex whorls, faint subsutural cord and opisthocline axial ribs with delicate spiral threads in interspaces, angled columella.

Description. Shell medium-sized, moderately slender (apical angle ~25°). Protoconch unknown. Teleoconch of about 10 whorls. Whorl profile weakly convex with steep, weakly concave subsutural ramp, periphery distinctly below mid-whorl. Suture weakly impressed, weakly undulating. Faint subsutural collar. Sculpture of moderately close-set, low, convex, opisthocline axial ribs not aligned axially (10: 13: 14). At least one indistinct, low varix per whorl. Spiral sculpture consisting of numerous delicate spiral threads overrunning axial ribs, most prominent in axial interspaces, fading over axial ribs. Last whorl attaining ~40% of total height, axial ribs fading over convex base, no basal angulation, no peribasal cord, numerous spiral threads over base. Aperture ovate, columella straight, angled at transition to parietal area. Fasciole short, broad, with prominent growth lines. Outer lip not preserved. Columellar callus indistinct. No parietal callus. No umbilicus.

Discussion. This species is slightly reminiscent of Hemiacirsa oscari (De Boury in Cossmann, 1912). They are distinguished by the fewer, relatively sharper axial ribs in H. oscari . Moreover, the ribs in H. oscari are opisthocyrt whereas they are opisthocline in Acirsa koskeridouae sp. nov. In addition, the whorls of Hemiacirsa oscari are higher and more convex. Acirsa corrugata ( Brocchi, 1814) , from the Pliocene of Italy, is higher, has more prominent spiral cords and an angled base (see Pinna & Spezia 1978: pl. 59: fig. 3).

Paleoenvironment. Shallow marine, inner neritic with sea grass (own data, M.H.).

Distribution in Central Paratethys. Badenian (Middle Miocene): Vienna Basin: Steinebrunn ( Austria) (hoc opus).