Tyrrhenocythere pontica (Livental)

RAUSCH, LEA, STOICA, MARIUS & LAZAREV, SERGEI, 2020, A Late Miocene - Early Pliocene Paratethyan Type Ostracod Fauna From The Denizli Basin (Sw Anatolia) And Its Palaeogeographic Implications, Acta Palaeontologica Romaniae 16 (2), pp. 3-56 : 27

Tyrrhenocythere pontica (Livental) in Agalarova et al., 1961

Fig. 17 a-e

1961 Cythereis pontica Livental in litt.- Agalarova et al., 1961 (pl. LXXXII, figs. 2, 3a, b, c; pl. LXXXV, figs. 2-4.

1975 Trachileberis pontica (Livental) - Vekua, pl. XV, figs. 1 a,b, 2 a, b, 4.

1977 Tyrrhenocythere pontica (Livental) - Krstić, pl. II, figs. 1, 2.

1982 Tyrrhenocythere pontica (Livental) - Olteanu, p. 53, pl. VI, figs. 1, 2.

1989 Tyrrhenocythere pontica (Livental) - Olteanu, pl. XII, figs. 1, 2.

1989 Tyrrhenocythere pontica (Livental) - Stancheva, p. 20, pl. 6, fig. 4.

1995 Tyrrhenocythere pontica (Livental) - Olteanu, p. 301, pl. 25,fig. 8.

1999 Tyrrhenocythere pontica (Livental) - Gliozzi, p. 201, pl. II, fig. c-1; pl. IIId.

2001 Tyrrhenocythere pontica (Livental) - Olteanu, pl. II, fig. 1.

2013 Tyrrhenocythere pontica (Livental) - Van Baak et al., p. 124, pl. 4 b, 21.

Description. The valve has an oblong shape in lateral view with the maximum height within the anterior third. The dorsal margin is almost straight, slightly arched on male valves and more or less inclined towards the posterior, whereas in females it is slightly concave. The anterior margin is broadly rounded and connects smoothly to the ventral margin that is lightly concave which can best be seen from the internal view. The posterior margin is weakly pointed and bears a more or less pronounced shoulder, which starts midheight and is rounded underneath and continues smoothly onto the ventral margin. Above the apex the posterior is concave. Along the ventral margin runs a well pronounced ridge (crest) that originates at the lower part of the anterior margin and ends abruptly on the posterodorsal angle axis. The crest is more elongated in males and a bit shorter and higher up at the posterior in females. Juvenile stages have a shorter crest but visibly located higher and pointed towards the posterior end. The surface of the valve is covered with unequally sized polygonal meshes that increase in size towards the anterior-and posterior margin. Within the main polygonal network, a secondary ornamentation is observed, especially in areas close to the anterior and posterior. Along the rim, the ornamentation forms parallel rows. The hinge is heterodont. Dimension: L = 0,52 – 1,08 mm, H = 0,32 – 0,60 mm, the minimum sizes include juveniles too.

Chronostratigraphical and geographical distribution. Inside the Eastern Paratethys this species is known from late Miocene – early Pleistocene records. It has been described from middle Pontian – early Dacian of the Dacian Basin of Romania and Bulgaria, Pontian deposits of the Euxinic Basin of southern Ukraine and Turkey and the Apsheronian of the South Caspian Basin of Azerbaijan ( Agalarova et al., 1961; Vekua; 1975; Krstić, 1977; Olteanu, 1982, 1990; Tunoğlu and Ünal 2001; Van Baak et al., 2013). Outside Paratethys the species has been mentioned, e.g., from upper Messinian Lago-Mare deposits of the Le Vicenne Basin in Italy ( Gliozzi, 1999), Malaga Basin of Spain ( Guerra-Merchán et al., 2010), the latest Miocene or Early Pliocene of the greek island Kos ( Guernet et al., 1976), the latest Messinian of Corsica and the Rhone Basin of France ( Carbonnel, 1978). It frequently occurs in the Quaternary of the Danube Delta ( Olteanu, 1995).

Ecology. The living representatives of the genus are generally occurring in mesohaline waters (9 - 13 ‰) but also tolerate lower salinities. They can be found at a variety of depths ranging from 0-30m ( Krstić, 1977 for T. amnicola (Sars)) down to 200m in the Caspian Sea (Yassini and Ghahremann, 1976 for T. scitula ). Krstić (1977) estimated that the fossil species of Tyrrhenocythere lived in shallow waters with a salinity ranging from 5 – 15 ‰.

Figures

Fig. 17a-e Tyrrhenocythere pontica; a LV, external view, ♂; b RV, external view, ♀; c LV, external view, ♀; d LV, external view, A2 juvenile; e LV, external view, A3 juvenile; f-j Tyrrhenocythere aff. pontica; f LV, external view, ♂; g LV, external view, ♀; h LV, external view, A1 juvenile; i RV, external view, A2 juvenile; j LV, external view, A3 juvenile; k, l Tyrrhenocythere aff. ruggierii; k LV, external view, ♀; l RV, external view, ♀; (specimens a-e from section B, samples 36,6 m – 61,5 m; specimens f-j from section A, sample 15 m; specimens k-l from section B, sample 65 m).