Hemicerithium kovacsi, Harzhauser & Guzhov & Landau, 2025

Hemicerithium kovacsi sp. nov.

Fig. 67A View FIGURE 67

? Plesiotrochus sp. — Kovács & Vicián 2016: 237, pl. 1, fig. 9.

Type material. Holotype, INV 2016.2, SL: 9.0 mm, MD: 4.2 mm, Hungarian Natural History Museum , Budapest, Fig. 67A View FIGURE 67 .

Type locality. Esztergom-Szentgyörgymező ( Hungary), Esztergom Basin .

Type stratum. Clayey silt.

Age. Egerian (Late Oligocene/Early Miocene).

Etymology. In honor of Zoltán Kovács (Budapest), who detected this species and described it together with his colleague Zoltán Vicián (Budapest) in open nomenclature.

Diagnosis. Small, weakly coeloconoid shell with marked angulation below mid-whorl, broad subsutural ramp, axial sculpture of broad varices and large blunt tubercles at periphery fading towards adapical suture, spiral sculpture of numerous narrow spiral cords, strong peribasal cord.

Description. Small, conical shell of nine teleoconch whorls with weakly coeloconoid spire; apical angle 30°. Protoconch unknown. Early teleoconch whorls angulated above abapical suture with broad subsutural ramp, broad axial ribs and narrow spiral cords (surface abraded). Abapically, axial ribs weaken over subsutural ramp, broaden below, widely spaced, separated by interspaces of about equal width, forming large, rounded tubercles at periphery. Spiral sculpture of numerous (about 17) narrow spiral cords separated by narrow grooves. Two to three prominent varices per whorl. Suture narrowly incised, undulating. Base concave, with prominent peribasal cord. Last part of last whorl not preserved.

Discussion. This is the stratigraphically earliest Plesiotrochidae species from the Egerian (Chattian/Aquitanian) of the Paratethys Sea. Despite the fragmentary preservation, we formally introduce this species as new as it can clearly be distinguished from congeneric Oligocene and Miocene species. Several species are known from the Oligocene and Early Miocene of the Northeastern Atlantic and the Mainz Basin ( Lozouet et al. 2001; Lozouet & Maestrati 2012, for nomenclatorial rectifications see Pacaud 2019). Of these, the Oligocene Hemicerithium adultum ( Grateloup, 1845) (= H. subtrochleare d’Orbigny, 1852 ) has comparable sculpture but is stockier with lower spire whorls and has weaker spiral sculpture (see Lozouet & Maestrati 2012: figs 181/6–9). The Oligocene Hemicerithium dissitum ( Sandberger, 1858) differs in its convex whorls with weaker angulation and the weak axial sculpture (see Lozouet & Maestrati 2012: figs 181/2–5). The Early Miocene Hemicerithium resectum (de Basterot, 1825) (= H. fallax Grateloup, 1832 ) is a very variable species ( Cossmann & Peyrot 1922: pl. 5, figs 78–83, 89) and shells described by Cossmann & Peyrot (1922) as variety pernodulosum are superficially reminiscent of Hemicerithium kovacsi sp. nov. The periphery of Hemicerithium resectum , however, is much closer to the abapical suture and it bears more numerous axial ribs on early teleoconch whorls. Among the Paratethyan species, the Middle Miocene Hemicerithium olgae ( Boettger, 1902) also has axial ribs that form blunt nodes, but these nodes are placed at the abapical suture, and the species differs in its faintly angled base. The Middle Miocene Hemicerithium banaticum ( Boettger, 1902) lacks an angulated periphery and Hemicerithium evae ( Boettger, 1902) lacks prominent axial ribs.

Paleoenvironment. The assemblage from Esztergom-Szentgyörgymező contains molluscs from various shallow marine environments ( Kovács & Vicián 2016).

Distribution. Only known from the Egerian of the Central Paratethys Sea.

Central Paratethys Sea. Egerian (Late Oligocene/Early Miocene): Esztergom Basin: Esztergom-Szentgyörgymező ( Hungary) ( Kovács & Vicián 2016).