Ervilia dissita dissita (Eichwald, 1830)

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 : 21-22

Ervilia dissita dissita (Eichwald, 1830)

Figure 3.12 -13

1830 Crassatella dissita Eichwald , p. 206; 1853, p. 92, pl. 5, fig. 24.

1932 Ervilia podolica var. dissita (Eichwald) ; Davitashvili, p. 37, pl. 1, figs. 17-23.

1935 Ervilia dissita (Eichwald) ; Kolesnikov,p. 39, pl. 3, figs. 9-16.

1955 Ervilia pusilla dissita (Eichwald) ; Merklin and Nevesskaya, p. 80, pl. 22, figs. 13-21.

1993 Ervilia dissita dissita (Eichwald) ; Nevesskaya, Goncharova, Paramonova, Popov, Babak, Bagdasaryan and Voronina, p. 306, pl. 72, figs. 37-40.

Material. 13 specimens from layer 1 (10 left valves, 13 right valves).

Description. Oval-triangular shell (LS up to 13.5 mm; HS up to 10 mm; Con. up to 2.2 mm), equivalve. Closure of the valves is dense. Umbo is high, pointed, turned to posterior edge and, usually, displaced to the anterior edge. The anterior branch of the hinge edge is gently sloped and without noticeable angles merges into a widely rounded anterior edge. The posterior branch of the hinge edge is concave and has an S-shaped form without noticeable angles, merges into a rounded, sometimes abducted downward, posterior edge. Ventral edge is slightly convex. Valves are usually inequilateral, slightly convex. The keel is roundish, poorly noticeable. The shell surface is covered with growth lines, which sometimes look like wrinkles.

Hinge area is short. There is one well-developed cardinal tooth and single poorly developed lateral teeth in the right valve hinge. There are two weakly developed cardinal teeth and one posterior lateral tooth in the left valve. There is a triangular deepening for the inner ligament on both valves, closer to the posterior edge. The inner surface of the shell is with a clear pallial line, sinus rounded, not deep, pallial tongue with a restriction. The scars of the anterior and posterior muscles are round-oval, clear, and approximately equal in size. Variability. It is expressed in the form of the posterior edge, narrow to broadly rounded, and in the umbo position. Lateral teeth can be reduced, both in the right and left valves.

Region of distribution and age. Early and Middle Sarmatian of south of Eastern Europe, Central Europe and Turkey (Nevesskaya et al., 1993).

Figures

FIGURE 3. Assemblage of the Middle Sarmatian (Bessarabian) marine bivalves (layer 1). 1-2, Polititapes ponderosa (d’Orbigny, 1844). 3-4, Polititapes vitaliana (d’Orbigny, 1844). 5-6, Sarmatimactra fabreana (d’Оrbigny, 1844). 7-8, Obsoletiformes obsoletum ingratum (Kolesnikov, 1929). 9-10, Obsoletiformes obsoletum obsoletum (Eichwald, 1830). 11, Plicatiforma fittoni fittoni (d’Orbigny in Murchison et al., 1845). 12-13, Ervilia dissita dissita (Eichwald, 1830).