Cyprideis ex. gr. torosa (Jones, 1850)

Fig. 16 a-j

1850 Cyprideis torosa - Jones, 2, 6: 27; pl. 3: 6a-e.

1925 Cyprideis littoralis nov. comb. - Sars, p. 9: 155; pls. 71, 72:1.

1996 Cyprideis torosa Jones- Boomer et al., p.83, fig. 4, J-N.

2000 Cyprideis torosa Jones- Meisch, p. 459, fig. 188- 189.

2005 Cyprideis torosa Jones- Matzke-Karasz & Witt, p. 128, pl. 3, fig. 8-11.

2005 Cyprideis torosa f. torosa Jones- Viehberg, p. 67, fig. 7, 8.

2015 Cyprideis ex. gr. torosa - Van Baak et al., p. 603, fig. 8 (19-27).

2018 Cyprideis ex. gr. torosa - Jorissen et al., p. 13, fig. 10 (9-20).

Description. The carapace has a subovate to elongated shape in lateral view and a slightly arched dorsal margin that gently slopes towards the rounded posterior end. The anterior border is broadly rounded as well but weakly cut off in the upper part. The greatest width of the carapace is slightly in front of the mid-length. The male valves are a bit more elongated and narrower in the posterior area. The valves surface varies from having a fine reticulation to pitted ornamentation and can have up to 6 tubercles, variable in form, number and position. They do not seem to occur symmetrical and are frequently absent. The inner lamella is narrow. The muscle scar and the hinge are typical for the genus. Dimension: L = 0,69 – 1,04 mm, H = 0,37 – 0,57 mm, the minimum sizes include juveniles too.

Chronostratigraphical and geographical distribution. C. torosa is one of the most common ostracod species observed in brackish coastal waters of Europe, Western and Central Asia, the Mediterranean region of North Africa, the Middle East as well as North America and Central Africa (Meisch, 2000). The fossil record goes back to the Miocene. C. torosa first appeared in the Eastern Paratethys in the late Volhynian (early Sarmatian s.l.) and in Sarmatian s.str. in the Central Paratethys (Carbonnel and Jiříček, 1977; Jiříček, 1983). The species has been commonly observed in Khersonian - Romanian brackish water deposits of the Slănicul de Buzău section as well as in the freshwater sediments of Romanian deposits (Van Baak et al., 2015; Jorissen et al., 2018; Lazarev et al., 2020 (submitted)). In the Mediterranean the species was first recognized in middle Tortonian brackish water deposits of Crete in the Eastern part of the Mediterranean (Sissingh, 1974).

Ecology. C. torosa inhabits mainly marine brackish waters with fluctuating salinities but is also found in a greater range of salinities from freshwater to fully marine and even hypersaline waters (over 60 ‰) (Meisch, 2000). It occurs in coastal ponds, lakes, marginal marine environments and prefers mud or sandy substrates but also can be found on pure sand or algae (Meisch, 2000) down to depths of 30 m. Salinities ranging between 2 - 16,5 ‰ are reported to offer the optimal conditions for population development (Meisch, 2000; Wagner, 1964).