Dreissena sp. 1

Neubauer, Thomas A. & Wesselingh, Frank P., 2023, The Early Pleistocene freshwater mollusks of the Denizli Basin (Turkey): a new long-lived lake fauna at the crossroads of Pontocaspian and Aegean-Anatolian realms, Zitteliana 97, pp. 53-88 : 53

Dreissena sp. 1

Fig. 17K-N

Material.

Sample 2: 2 valves (RGM 962703, 962704), 49 valves (RGM 1310847), 2 valves (SNSB-BSPG 2023 XII 24); sample 3: 6 valves (RGM 1310848).

Description.

Shell large, wide, and distinctly flat. Exterior smooth, apart from fine growth lines. Dorsal margin long, almost straight, with robust but rounded posterodorsal angle. Through ontogeny, semidiameter shifts with almost straight line 45° from umbo toward posterior margin (which is broken in all specimens). In some specimens, slight byssal inflection may be developed on ventral margin, which is otherwise almost straight. Plane of symmetry between valves appears to be not entirely flat. Hinge plate robust, wide, and flat.

Dimensions.

Length c. 20 mm (all material is broken).

Remarks.

The smooth appearance and the presence of a very slight byssate inflection are characters that may point to a relationship with the Pontocaspian Dreissena rostriformis Deshayes, 1838 species group ( Wesselingh et al. 2019). However, the very wide nature of specimens is unknown from this group and resembles superficially Congeria species.

Distribution.

Dreissena sp. 1 is only known from the Lower Pleistocene Kolankaya Formation of the Denizli Basin.

Figures

Figure 17. Dreissenidae of the Kolankaya I fauna. A, B. Dreissena kairanderensis (Oppenheim, 1919), RGM 962699, sample 2. C, D. D. kairanderensis, RGM 962701, sample 2. E, F. D. kairanderensis, RGM 962702, sample 2. G, H. D. kairanderensis, RGM 962700, sample 2. I, J. D. kairanderensis, RGM 962698, sample 2. K, L. Dreissena sp. 1, RGM 962703, sample 2. M, N. Dreissena sp. 1, RGM 962704, sample 2. Scale bar: 2 mm.