Polititapes ponderosa (d’Orbigny, 1844)

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 : 19-20

Polititapes ponderosa (d’Orbigny, 1844)

Figure 3.1-2

1844 Venus ponderosa d’Orbigny , p. 483, pl. 5, figs. 12-14.

1932 Tapes gregarius var. ponderosa (d’Orbigny) ; Davitashvili, p. 33, pl. 2, figs.

1-6.

1935 Tapes gregarius (Partsch in Goldfuss, 1934); Kolesnikov, p. 75, pl. 8, figs. 25-27; [non Venus gregaria Partsch in Goldfuss, 1841 = Polititapes tricuspis (Eichwald, 1829) ].

1955 Tapes gregarius (Partsch in Goldfuss, 1934); Merklin, Nevesskaya, p. 61, pl. 17, figs. 11-16.

1969 Tapes tricuspis ponderosus (d’Orbigny) ; Kojumdgieva, p. 53, pl. 18, figs. 1-3.

1993 Veneripis (Polititapes) ponderosa (d’Orbigny) ; Nevesskaya, Goncharova, Paramonova, Popov, Babak, Bagdasaryan and Voronina, p. 188, pl. 47, figs. 5-8.

2013 Polititapes ponderosa (d’Orbigny) ; Neubauer, Harzhauser and Mandic, p. 322.

2013 Polititapes ponderosa (d’Orbigny) ; Schnei- der, Mandic and Harzhauser, p. 195.

Material. 12 specimens from layer 1 (12 left valves, 2 right valves).

Description. Shell is round to oval (LS is up to 30.3 mm; HS is up to 25.5 mm; Con. is up to 8 mm), large, thick-walled, equivalve. Closure of the valves is dense. Umbo is high, shifted, and strongly turned toward the anterior edge. The anterior branch of the hinge is short, slightly inclined, merges smoothly into a rounded anterior edge. The posterior branch of the hinge is long, smoothly inclined, transforming into the posterior edge with a noticeable blunt angle. Posterior edge broadly rounded. Ventral edge convex, smoothly transforming into adjacent edges, without visible angles. Valves are inequilateral, slightly convex. There is a weak rounded keel from the umbo to the lower posterior corner. Growth lines are clear, often erased on most of the shell, preserved only near the ventral, anterior, and posterior edges. The length of the nymph occupies about two-thirds of the posterior branch of the dorsal edge.

Hinge area is wide, wavy curved. Hinge is massive. Both right and left valve hinge consists of the three cardinal teeth; lateral teeth are absent. The central tooth is a most developed, larger than others are, and divided by a shallow groove. The anterior tooth of the right valve and the posterior of the left valve are smaller; a groove may be developed. The posterior tooth of the right valve and the anterior tooth of the left valve are the weakest; a groove is absent.

The inner surface of the shell with a clear pallial line, the sinus reaches the posterior third of the shell. Muscular scars are oval, deep, and approximately equal in size. Small oval-rounded muscular scars, arranged in a semicircle, are clearly visible under the umbo.

Region of distribution and age. Middle-Late Miocene of Europe. Middle Sarmatian (Bessarabian) of the Eastern Paratethys (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).