Pseudamnicola nympha (Eichwald, 1850)

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 : 9-10

Pseudamnicola nympha (Eichwald, 1850)

Figure 4.5

1850 Paludina nympha : Eichwald, p. 135, pl. 10, fig. 27.

1935 Amnicola nympha (Eichwald) ; Kolesnikov, p. 218, pl. 27, figs. 38-40.

Material. 6 specimens from layer 1 and 1 specimens from layer 3.

Description. The shell is conical with a pointy apex (HS is 2.5 mm, WS is 1.75 mm), moderately high (WS/HS is 0.6), consisting of 5 rounded whorls, separated by an almost horizontal moderately deep suture. The last whorl is rounded and is about 0.7 of the shell height (HLW/HS). Aperture is oval, may be slightly oblique, pointed in the upper part (WA/HA is 0.7), and is approximately 0.4 of the total shell height (HA/HS). Aperture edges are thin, not thickened. Umbilicus is slit-like, covered by the inner edge of aperture (the degree of cover can vary from almost completely open to practically closed). The shell surface is smooth; growth lines are visible. There are some shells with a weak spiral striation on the last whorl.

Remarks. Shells with a weak striation may refer to P. cyclostomoides Sinzov, 1880 . According to Kolesnikov (1935), the main difference between these two species is expressed in the presence of sharp spiral ribs on the last two whorls in P. cyclostomoides . Because P. nympha may also have such ribs, even though not so prominent, our forms were assigned to the described species.

Pseudamnicola nympha (Eichwald, 1850) was placed to the genus Amnicola by Kolesnikov (1939). According to O. Anistratenko and V. Anistratenko (2012), this species belongs to the family Hydrobiidae on account of the embryonic shell structure. Its generic affiliation needs to be specified. Lukeneder et al. (2011) attributed P. cyclostomoides to genus Pseudamnicola . As P. cyclostomoides is very close to P. nympha we attribute this taxon also to genus Pseudamnicola .

Region of distribution and age. Middle Sarmatian (Bessarabian) of the Eastern Paratethys (O. Anistratenko and V. Anistratenko, 2012).

Figures

FIGURE 4. Assemblage of the Middle Sarmatian (Bessarabian) marine gastropods (layers 1 and 2). 1, Acteocina lajonkaireana (Basterot, 1825). 2, Acteocina okeni (Eichwald, 1850). 3, Retusa melitopolitana (Sokolov, 1899). 4, Hydrobia elongata Eichwald, 1830. 5, Pseudamnicola nympha (Eichwald, 1850). 6, Dorsanum duplicata opinabile (Kolesnikov, 1932). 7, Dorsanum corbiana (d’Orbigny, 1844). 8, Dorsanum ignobile (Kolesnikov, 1932). 9, Gibbula (Gibbula) pseudoangulata (Sinzov, 1875). 10, Gibbula (Sarmatigibbula) podolica (Du Bois de Montpéreux, 1831).