Mohrensternia sarmatica Friedberg, 1923

Kowalke, Thorsten & Harzhauser, Mathias, 2004, Early ontogeny and palaeoecology of the Mid-Miocene rissoid gastropods of the Central Paratethys, Acta Palaeontologica Polonica 49 (1), pp. 111-134 : 129

Mohrensternia sarmatica Friedberg, 1923

Mohrensternia sarmatica sp. nov.; Friedberg 1923: 389, pl. 23: 8–10.

Mohrensternia sarmatica Friedberg ; Papp 1954: 35.

Mohrensternia sarmatica Friedberg ; Korobkov 1955: pl. 21: 10.

Rissoa (Mohrensternia) inflata sarmatica Friedberg ; Boda 1959: 705, pl. 23: 12–14.

Mohrensternia sarmatica Friedberg ; Svagrovský 1971: 306–308, pl. 51: 1–10.

Material.— Four specimens from Siebenhirten , Lower Austria, IRSNB IG 23693 .

Description.—The small, not very slender, conical shell consists of 5–6 regularly increasing, rounded whorls with a maximum convexity in the median portion of the whorls or just below, causing an angulated shell outline. The shell measures up to 4.8 mm in height and up to 3 mm in width. Whorls are separated by marked, deep sutures. Sculpture consists of 12 strongly developed, stout, orthocline axial ribs, which diminish on the lower half of the last whorl. The base appears to be smooth. The last whorl forms about 50–60% of total shell height. The very thin aperture has a broad−oval to roundish outline with a prominent, pointed parietal portion.

The protoconch is not well preserved. It comprises about 2.5 well−rounded whorls and measures 0.38–0.4 mm in height and in maximum diameter. The diameter of the corroded initial whorl amounts to about 0.14 mm. The onset of the teleoconch is indicated by the less rounded, wavy outline of the whorls and by the formation of the adult sculpture of axial ribs.

Remarks.—According to Papp (1954), Mohrensternia sarmatica is closely related to M inflata and differs by a slightly more slender shell with fewer but more strongly developed ribs, causing a more angulate outline of the whorls. The axial ribs are orthocline, not sickle−shaped as in M. inflata . Mohrensternia sarmatica also differs in protoconch morphology (slightly smaller protoconch). In contrast to the interpretation of Papp (1954), who treats Mohrensternia soceni Jekelius, 1944 (p. 71, pl. 15: 4–6) as closely related with M. sarmatica , the latter differs distinctly by its smaller, more slender shell, comprising more and regularly increasing whorls, which are more strongly convex. The aperture of M. sarmatica is not detached from the spire and its protoconch is considerably smaller.

Mohrensternia sarmatica occurred in the Sarmatian of the Vienna Basin, the Styrian Basin, the Carpathian Foredeep, the Mid Danube Basin and in the Sarmatian of South−East Europe ( Svagrovský 1971).