Viviparus cf. karaganicus Volkova, 1939

Frolov, Pavel D., Danukalova, Guzel A. & Osipova, Eugenia M., 2018, Late Miocene molluscs of the Morskaya 2 site (Azov Sea region, Russia), Palaeontologia Electronica (a 20) 23 (1), pp. 1-32 : 12-14

Viviparus cf. karaganicus Volkova, 1939

Figure 5.4

1939 Viviparus karaganicus Volkova , p. 19, pl. 1, fig. 5.

1961 Viviparus karaganicus Volkova ; Bogachev, p. 277.

Material. 12 specimens from layer 3.

Description. The shell is oval-conical with pointed spire (HS is 7.0- 9.2 mm, average 8.0; WS is 7.8- 12.2 mm, median 9.8), high (WS/HS is 1.1-1.3, average 1.2), and consists of 5-5.5 flattened whorls separated by a shallow suture. The last whorl is rounded, and the bend is clearly visible in the middle of this whorl, it is about 2/3 or more of the shell height (HLW/HS is 0.9-1.0, average 0.96). Aperture has an ovoid form, pointed in the upper part (WA/ HA is 0.8-1.1, average 0.96), and is about 2/3 of the total shell height (HA/HS is 0.55-0.7; 0.69). Aperture edges are thin, not thickened. Umbilicus is closed. The shell surface is covered by fine hatching. Opercula were not found.

Remarks. Holotype is stored in the F.N. Chernyshev CNIGR Museum, N 5/5890. Viviparidae with slightly convex whorls and with an inflection on the last whorl are represented by several specimens. Viviparus conoides Mangikian, 1931 , from the Khersonian (late Sarmatian) of Ukraine (Gozhyk and Prisyazhnyuk, 1978, p. 59, pl. 36, figs. 7-10) resembles the present specimens but differs in less convex whorls and inflection that is more noticeable on the last whorl. Viviparus karaganicus Volkova, 1939 (pl. 2, fig. 5) from the Karaganian (Middle Miocene) of the North Caucasus has a conical shell with slightly convex whorls and with a smooth keel on the last whorl (Malchevskaya, 1985). Morphologically, this species is closest to the studied specimens. Because of the large age difference between specimens from the Morskaya 2 site and the type locality of the species, we use the open nomenclature for our specimens.

Region of distribution and age. Middle (Karaganian) and Late (Maeotian) Miocene. Stavropol Territory (Volkova, 1939) and the Rostov Region.

Figures

FIGURE 5. Assemblage of the Maeotian freshwater molluscs (layer 3). 1, Borysthenia cf. pronaticina (Lindholm, 1932). 2-3, Lithoglyphus acutus Cobălcescu, 1883; 2, smooth shell; 3, shell with keel. 4, Viviparus cf. karaganicus Volkova, 1939. 5, Viviparus cf. maeoticus (Bogachev and Shishkina, 1919). 6, Lymnaea sp. 7, Sphaerium rivicola Lamarck, 1818. 8, Gyraulus cf. acronicus (Ferrussac, 1807). 9-10, Bithyniidae, opercula.