Astyris, H. Adams & A. Adams, 1853

Harzhauser, Mathias & Landau, Bernard M., 2021, The Columbellidae (Gastropoda, Buccinoidea) in the Miocene Paratethys Sea — striking diversity of a negelected group, Zootaxa 5025 (1), pp. 1-75 : 61-62

Astyris ? agenta ( Harzhauser & Kowalke, 2002)

Figs 18B, C 1 –C 2

Mitrela [sic] agenta nov. sp. — Harzhauser & Kowalke 2002: 73, pl. 13, figs 14–16.

Mitrella agenta — Piller & Harzhauser 2005: 454.

Type material. Holotype. NHMW2001 z0058/0001, SL: 2.75 mm, MD: 1.1 mm, St. Margarethen ( Austria), illustrated by Harzhauser & Kowalke (2002, pl. 13, figs 14–15), Fig. 18B . Paratype: NHMW2001 z0059/0001a, SL: 2.7 mm, MD: 0.95 mm, St. Margarethen ( Austria), illustrated by Harzhauser & Kowalke (2002, pl. 13, fig. 16), Figs 18C 1 –C 2 .

Revised description. Shell tiny, moderately broad fusiform, with moderately high spire and high last whorl. Low conical protoconch of 2.7 convex whorls terminating in deep sinusigera (see Harzhauser & Kowalke 2002, fig. 16). Teleoconch of four smooth whorls, with weakly impressed suture. Spire whorls high, weakly convex with periphery slightly below mid-whorl. Last whorl subcylindrical, hardly contracting to short fasciole. Shell smooth or with low, broad, weakly opisthocline axial swellings on last whorl, fading out above mid-whorl. Aperture ovoid, moderately wide; aperture low with adapical termination slightly below periphery of last whorl. No columellar callus and denticles. Outer lip thin without denticles. Siphonal canal short, straight; siphonal notch deeply incised.

Shell measurements and ratios. SL: 2.75 mm, MD: 0.1 mm, AA: 37–44°, SL/MD: 2.4, AL/AW: 3.1, LWH/ AH: 1.4.

Discussion. This species was established within Mitrella , but the subcylindrical last whorl, the short siphonal canal and the low aperture are atypical for Mitrella . The absence of a labial pad and denticles is reminiscent of Astyris . See discussion for Astyris sarmatica ( Kojumdgieva, 1969) .

The origin of this species in the largely enclosed Sarmatian Sea is enigmatic, as it is only known from the middle Sarmatian, but unknown from lower Sarmatian strata. According to Harzhauser & Kowalke (2002) it might indicate an immigration from the Proto-Mediterranean Sea via a short-lived seaway. Its absence from other localities, however, might also be related to its minute size.

Palaeoenvironment. Shallow sublittoral carbonate sand ( Harzhauser & Kowalke 2002).

Distribution in Central Paratethys. Sarmatian (middle Miocene): Eisenstadt-Sopron Basin: St. Margarethen ( Austria) ( Harzhauser & Kowalke 2002).

Figures

FIGURE 1. A. Map of central and south–eastern Europe, representing the area that was partly covered by the Central Paratethys Sea. The white insert corresponds to the area that is restored in the palaeogeographic map below. B. Paleogeography of the Middle Miocene Paratethys Sea showing the most important sedimentary basins (NAFB: North Alpine Foreland Basin, E–Sopr B: Eisenstadt–Sopron Basin).

FIGURE 2. Measurements for shell morphology and whorl profiles. SL: shell length, MD: maximum diameter, AA: apical angle, LWH: last whorl height, AH: aperture height. AL: aperture length. AW: aperture width.

FIGURE 18. A1–A2. Astyris sarmatica (Kojumdgievam 1969), NHMW2020/0156/0001, Kronberg (Austria). 8 B. Asytris? agenta Harzhauser & Kowalke, 2002, NHMW2001z0058/0001, holotype, St. Margarethen (Austria). C2–C2. Astyris? agenta Harzhauser & Kowalke, 2002, NHMW2001z0059/0001a, paratype, St. Margarethen (Austria).