Hydrobiidae sp. indet., 1973

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

Hydrobiidae sp. indet.

Fig. 13A-C

Material.

1 shell (RGM 1310799) from sample 2.

Dimensions.

4.25 × 2.56 mm.

Remarks.

The single specimen from Denizli closely resembles the extant Radomaniola caputlacus ( Schütt & Şeşen, 1993), originally described as a species of Orientalina from eastern Anatolia. Both share the conical shape with weakly convex whorls and the simple ovate aperture. However, Radomaniola caputlacus is with 2.2 mm shell height ( Schütt and Şeşen 1993) only about half the size of the Denizli shell. Larger species (up to 4 mm) of that genus are known from the Balkan Pensinula, where it is considerably more diverse, but these species differ clearly from the Denizli shell ( Delicado and Hauffe 2022).

Another similar species is the fossil Bithynia giralanensis Oppenheim, 1919 (pl. 10, fig. 1), described from the Denizli Basin. However, that species is much larger (10 × 8 mm) at about the same number of whorls and bears a weak subsutural band; also, the shell is slightly broader and has a shallower base. Given these features, classification in the genus Bithynia is unlikely. Considering the poor preservation of Oppenheim’s material as cast and the apparent loss of the type material (see Introduction), the name Bithynia giralanensis Oppenheim, 1919 should be considered a nomen dubium.

Yet another similar species is Bania urosevici ( Pavlović, 1931) from the middle Miocene of Serbia in terms of general shape, the angulation, and the tilt of the aperture ( Neubauer et al. 2020). The Denizli shell is, however, much larger (height of B. urosevici ~1.8 mm). Moreover, no Bania species is known until now from Turkey or deposits younger than Tortonian. The shell similarity may rather be due to convergence.

Finally, the species shares similarities with species of Shadiniinae , e.g., Persipyrgula saboori ( Glöer & Pešić, 2009), which has a similar size, number of whorls, and shell shape, but more rounded whorls and a larger aperture ( Delicado et al. 2016).

Given the poor preservation of our material and the overall difficulty of assigning fossil hydrobiids with few morphological characteristics to genera and even subfamilies, we refrain from a tentative placement in any of the abovementioned taxa.

Subclass Heterobranchia Burmeister, 1837

Informal group "Lower Heterobranchia " sensu Bouchet et al. 2017

Superfamily Valvatoidea Gray, 1840

Family Valvatidae Gray, 1840

Figures

Figure 13. Hydrobiidae of the Kolankaya I fauna. A-C. Hydrobiidae sp. indet., RGM 1310799, sample 2. Scale bar: 1 mm.