Graecoanatolica alcicekorum, Neubauer & Wesselingh, 2023

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

Graecoanatolica alcicekorum sp. nov.

Fig. 6A-E

Etymology.

Named in honor of Hülya and M. Cihat Alçiçek, esteemed Turkish geologists with long research background in the Denizli Basin, for their continuing support and friendship.

Holotype.

RGM 962617 (Fig. 6A-E ). Babadağ river valley along the Babadağ-Sarayköy road, c. 2.4 km NW of the town of Babadağ, Denizli, Turkey; sample 2 (37°50'44.5"N, 28°52'51.3"E). Kolankaya Formation, Lower Pleistocene, Gelasian.

Additional material.

None (holotype only).

Diagnosis.

Slender, weakly ovoid shell with slightly tapered last whorl, adnate whorls with thin suture, faint subsutural concavity in late ontogeny, sinuate outer lip, and sigmoidal growth lines.

Description.

Slender, ovoid hydrobiid shell, with 4.75 whorls. Protoconch consisting of c. 1 whorl, low domed with broad nucleus, weakly, finely-meshed malleate surface; sculpture fades out toward P/T transition; transition indicated by growth stop and onset of growth lines. Whorls moderately convex in early ontogeny; penultimate whorl exhibits nearly straight-sided upper whorl half and regularly convex lower half; last whorl, portion below suture weakly concave, producing weak constriction and slightly irregularly convex whorl profile. Last whorl attains 60% of shell height. Base ~45°, straight-sided. Aperture drop-shaped, tightly coiled, leaving no umbilicus; peristome not thickened or notably expanded; outer lip distinctly sigmoidal in lateral view. Growth lines sigmoidal, with opisthocyrt upper half and slightly weaker, prosocyrt lower half.

Dimensions.

2.21 × 0.97 mm (holotype, RGM 962617; Fig. 6A-E ).

Remarks.

The species’ shell shape and size, the protoconch size, the subsutural concavity, the ovoid aperture with thin, sinuate peristome, and the sigmoidal growth lines are characteristics typical of extant members of the genus Graecoanatolica . The co-occurring species of Iraklimelania share many of these attributes, but they both have more slender shells with relatively smaller last whorls and larger protoconchs (1.2 whorls compared to 1 whorl).

The only fossil species of the genus was previously reported as G. denizliensis (Taner, 1974a) by Wesselingh et al. (2008) from the overlying " Didacna Beds" (= Kolankaya II fauna). The specimens, however, differ from true " Hydrobia " Graecoanatolica denizliensis in the much smaller, ovoid shell with strongly convex whorls. The original species described by Taner is a large hydrobiid (7 mm) with moderately convex whorls and elongated aperture. The species of Wesselingh et al. (2008), which is currently without a name but fits well in the genus Graecoanatolica , differs from the new species in the slightly broader shell, the more convex whorls, and the presence of a narrow umbilicus.

Graecoanatolica alcicekorum sp. nov. resembles several extant representatives of the genus. Shells of the North Macedonian Graecoanatolica macedonica Radoman & Stankovič, 1979 and the Greek G. vegorriticola ( Schütt, 1962) are similarly slender, but whorls have a regularly convex profile. The Turkish G. dinarica Kebapçı, Koca & Yıldırım, 2012 has a shell with highly convex whorls, a slightly irregularly shaped last whorl and a smaller aperture ( Kebapçı et al. 2012). Graecoanatolica lacustristurca Radoman, 1973b (the type species) and G. tenuis Radoman, 1973b, both also described from Turkey, have conical shells with broad, blunt apex and a narrow umbilicus ( Kebapçı et al. 2012).

The genus was recently placed in Caspiinae by Delicado et al. (2023) based on a comprehensive phylogenetic analysis.

Distribution.

So far only known from the Early Pleistocene of the Denizli Basin.

Figures

Figure 6. Caspiinae (Hydrobiidae) of the Kolankaya I fauna. A-E. Graecoanatolica alcicekorum sp. nov., holotype, RGM 962617, sample 2. F-I. Graecoanatolica? sp., RGM 1365349, sample 1. Scale bars: 1 mm (1 - D, F, G); 100 μm (E, H, I).