Theodoxus aff. pilidei ( Tournouer , 1879)

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

Theodoxus aff. pilidei ( Tournouer, 1879)

Fig. 4A-H

Material.

2 specimens (RGM 962608, RGM 1310796), 2 specimens and 1 fragment (RGM 1310842), 1 specimen (SNSB-BSPG 2023 XII 3); all from sample 2.

Dimensions.

1.97 × 2.69 mm (RGM 962608; Fig. 4A-D, H ), 3.66 × 3.88 mm (RGM 1310796; Fig. 4E-G ).

Remarks.

Our material contains two moderately preserved specimens that exhibit a high variability in spire height and angulation. The low-spired morphotype (Fig. 4A-D, H ) resembles Theodoxus pilidei ( Tournouër, 1879), originally described from Pliocene or Lower Pleistocene strata of the Dacian Basin ( Wenz 1942; Pană et al. 1981; Pană 2003; Papaianopol and Marinescu 2003), in terms of the general ovoid shell shape with depressed spire and the strong, papery lamellae. The illustrations of Pană et al. (1981) show quite some variability in the morphology of T. pilidei , including the expression of sculpture, which can be weak or nearly absent in some specimens. However, our material differs from that species particularly in the presence of a distinct angulation, which results in a nearly flat, apical plane. Specimens with elevated spire even show two angulations separated by a concave whorl flank (Fig. 4E-G ). From the little material we have available it is difficult to judge the species’ range of variability as well as make a taxonomic assignment. The distinct angulation present in our material, however, makes an affiliation with T. pilidei unlikely.

Another similar species is Theodoxus boteani (Porumbaru, 1881), which has a similar type of sculpture but more globular shells ( Pană 2003). The extant, allegedly subterranean Theodoxus gloeri Odabaşi & Arslan, 2015 from Eskişehir region (Turkey), which also exhibits papery lamellae, differs in a slightly higher spire and the absence of an angulation ( Odabași and Arslan 2015; Sands et al. 2020). Possibly our material signifies a new species.

Subclass Caenogastropoda Cox, 1960

Order unassigned

Superfamily Cerithioidea Fleming, 1822

Family Melanopsidae H. Adams & A. Adams, 1854

Figures

Figure 4. Neritidae of the Kolankaya I fauna. A-D, H. Theodoxus aff. pilidei (Tournouer, 1879), RGM 962608, sample 2. E-G. T. aff. pilidei, RGM 1310796, sample 2. Scale bars: 1 mm.