Semicassis szilviae, Kovács & Vicián, 2017

Kovács, Zoltán & Vicián, Zoltán, 2017, Middle Miocene Tonnoidea and Ficoidea (Caenogastropoda) assemblages from Letkés (Hungary), Fragmenta Palaeontologica Hungarica 34, pp. 75-104 : 82-84

Semicassis szilviae n. sp.

( Figs 18–24 )

Holotype – PAL2017.58.1., Hungarian Natural History Museum , Department of Palaeontology and Geology, (SL 21.5, MD 14.5 ) (donation of Tamás Hirmetzl) ( Figs 21–22 ).

Paratypes – 1st: Coll. Z. Vicián (SL 17, MD 11.5 ) ( Figs 23–24 ), 2nd: Coll. T. Hirmetzl (SL 26, MD 18 ) ( Figs 18–20 ), 3rd: HNHM PAL 2017.59 .1., 4th: PAL 2017.60.1 .

Type strata – Lower Badenian (Middle Miocene) clayey sand (Sámsonháza Formation).

Type locality – Letkés, W Börzsöny Mts, N Hungary.

Derivation of name – In honour of Szilvia Józan (Budapest).

Material – 14 specimens; HNHM: PAL 2017.58 .1., 59.1, 60.1., 11 specimens in private collections.

Diagnosis – Subovate shell, moderately elevated spire, multispiral protoconch, convex last whorl, wide aperture, denticulate outer lip, short, recurved siphonal canal, excavated columella with irregular folds, four narrow spiral cords on the ramp, one strong cord at the shoulder, deep, widely spaced grooves on the last whorl, weak varices and growth lines.

Description – Subovate shell (largest specimen: SL 27 mm). Moderately elevat- ed spire with concave outline, protoconch of 2.5 convex, smooth whorls, boundary delimited by slightly prosocline scar. Teleoconch of five whorls, subangulate spire whorls with concave sutural ramp. Convex last whorl (85% of the total height) with concave ramp, constricted at the base. Wide aperture, outer lip thickened by labral varix, 17 regular denticles on the inner edge, parietal callus expanded, thin. Short, deep, recurved siphonal canal, broadly excavated columella with irregular folds, short fasciole, abaxially recurved. Spiral sculpture of four narrow cords on the spire ramp and one strong cord at the shoulder, and deep, narrow, widely spaced grooves on the entire last whorl, weakening with ontogeny, axial sculpture of weak varices and growth lines with small tubercles at intersections.

Remarks – Based on overall morphology the new species is assigned to genus Semicassis . It is characterized by intraspecific variability in sculpture: some specimens have almost smooth last whorl. The species differs from S. laevigata by smaller and narrower shell, by higher, narrower, step-like spire, by less thickened labral varix, and by sculpture with axial ribs on the spire and regular spiral grooves on the last whorl. It also differs from the Early Miocene S. grateloupi (Deshayes) by narrower shell and spire, and by lack of broad spiral cords on the last whorl. The closest form is the small S. subsulcosa pedemontana Sacco from the Early Miocene of the Torino Hills (see FERRERO MORTARA et al. 1984, pl. 1, fig. 5); however, it differs by somewhat broader convex shell, thicker labral varix and stronger cords on the last whorl.

Distribution – Badenian: CP ( Hungary).

Figures

Figs 18–24. Semicassis szilviae n. sp. – 18–20. 2nd paratype, Coll. TH, SL 26, MD 18 (2.6×), apertural, apical and abapertural views. – 21–22. Holotype, HNHM PAL 2017.58.1., SL 21.5, MD 14.5 (3×), apertural and abapertural views. – 23–24. 1st paratype, Coll. ZV, SL 17, MD 11.5 (2.6×), abapertural and apertural views