Mohrensternia moesinensis Jekelius, 1944

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 : 128-129

Mohrensternia moesinensis Jekelius, 1944

Fig. 10C .

Mohrensterniamoesinensis sp. nov.; Jekelius 1944: 72, pl. 15: 19–22.

Mohrensternia moesinensis Jekelius ; Papp 1954: 36, pl. 5: 34–35.

Mohrensternia moesinensis Jekelius ; Svagrovský 1971: 310–311, pl. 52: 7–13.

Material.— Two specimens (original material in Papp 1954: pl. 5: 34, 35) from the Early Sarmatian of Eichkogel, Vienna Basin , NHMW 2002 z0029/0008.

Description.—The small, stout, rather egg−shaped shell comprises five slightly rounded whorls which are separated by moderately incised sutures. The shell measures up to 3 mm in height and up to 1.7 mm in width. The last two whorls are characterised by rather flat sides. Sculpture consists of closely spaced, sinuous growth lines and 10–12 weak, thin axial ribs with broad gaps between them, crossed by 8–10 more or less strongly developed spiral threads. The last whorl forms about 70–75% of total shell height. The holostomatous aperture is broad−conical to rounded. The parietal portion is pointed. A very narrow, slit−like umbilicus is present.

The large, conical protoconch comprises 2.75 slightly rounded whorls measuring 0.47 mm both in height and in maximum diameter. The embryonic shell comprises one whorl measuring 0.14–0.15 mm in maximum diameter and 0.03–0.04 mm in the width of the initial cap. Three very fine spiral stripes are visible. The embryonic shell is terminated by a slightly thickened rim. The subsequent larval shell appears to be smooth. It is terminated by a slightly projecting rim, which is slightly thickened in its adapical portion. The onset of the teleoconch is indicated by the formation of regular growth lines and axial ribs.

Remarks.—According to Svagrovský (1971), Mohrensternia moesinensis occurred in the Sarmatian of the Mid Danube Basin. Similar but larger−sized, broad−conical shells with more flattened whorls restricted to the Mysla Beds, Slovakia, have been described as Mohrensternia rectecostata by Svagrovský (1971).

Figures

Fig. 10. Two species of Mohrensternia Stoliczka, 1868. A, B. Mohrensternia inflata (Hörnes, 1856). A. Specimen (NHMW 2002z0029/0005) from the Early Sarmatian of Hollabrunn. B. Specimen (NHMW 2002z0029/0006) from the Early Sarmatian of Vienna−Nussdorf. Protoconch in lateral (B2) and apical (B3) views. The embryonic shell is separated from the subsequent larval shell by a slightly thickened rim. The onset of the teleoconch is indicated by the formation of weak axial folds, grading into regular axial ribs. C. Mohrensterniamoesinensis Jekelius, 1944. Specimen (collection A. Papp, NHMW 2002z0029/ 0008) from the Early Sarmatian of Eichkogel (C1). Lateral views of the protoconch of the same specimen as in C1 (C2, C3). The protoconch is terminated by a slightly projecting rim, which is slightly thickened in its adapical portion. Detailed apical view of the initial whorl of the same protoconch as in C3 (C4). The embryonic shell has fine spiral sculpture and it is terminated by a slightly thickened rim.