Harzhauseria schizopleura gen. et, 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

Harzhauseria schizopleura gen. et sp. nov.

Etymology.

Derived from the Ancient Greek syllables σχίζω ( skhízō) and πλευρόν ( pleurón), referring to the extraordinary sculpture, occasionally showing diverging ribs.

Holotype.

RGM 962613 (Fig. 8G-I, P ). 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.

Paratypes.

RGM 962614, SNSB-BSPG 2023 XII 7, SNSB-BSPG 2023 XII 8; all from the type locality and stratum.

Additional material.

Sample 1: 1 specimen with traces of intense growth lines rather than distinct ribs (SNSB-BSPG 2023 XII 9); sample 2: 6 nearly complete specimens, lacking aperture or last whorl, plus 13 fragments (RGM 1310851), 1 specimen with fragmented aperture and 2 fragments (SNSB-BSPG 2023 XII 10).

Diagnosis.

Small hydrobiine, conical, slender to slightly broader shell, with highly convex whorls that bear conspicuous irregular (straight to wavy, partly interfingering) ribs and large elliptical aperture.

Description.

Shell conical, slender to slightly broader, with 5 highly convex whorls. Protoconch smooth, consisting of c. 1.25 regularly coiled whorls; P/T transition marked by distinct growth stop. Numerous, weak, regularly shaped axial ribs develop on first teleoconch whorl. Ribs soon become irregular, variably spanning full whorl height or only parts, partly interfingering with each other (Fig. 8G-I ) or they become sigmoidal (Fig. 8J-L ). Distance and intensity of ribs also varies across specimens. Sometimes, rib tops are abraded, creating illusion of two ribs merging near upper and lower suture, leaving narrow concavity in between. Last whorl attains 60-64% (n = 2) of total shell height. Base ~45°, straight-sided. Aperture relatively large, well-rounded, elliptical; peristome weakly and equally thickened; umbilicus narrow. Growth lines faint.

Dimensions.

3.50 × 2.23 mm (holotype, RGM 962613; Fig. 8G-I, P ); 3.69 × 1.96 mm (paratype, RGM 962612; Fig. 8J-L ).

Remarks.

There is considerable morphological variability in the little material available to us. This concerns both shell shape and the expression of the ribs. However, it is well known that species of Hydrobiinae , such as the (probably related) genus Ecrobia , are morphologically highly variable, which often complicates establishing species boundaries (e.g., Wesselingh et al. 2019; Andreeva et al. 2022).

Distribution.

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

Figures

Figure 8. Hydrobiinae (Hydrobiidae) of the Kolankaya I fauna. A-C, Q. Ecrobia sp. RGM 962612, sample 2. D-F. Ecrobia sp. SNSB-BSPG 2023 XII 6, sample 2. G-I. P. Harzhauseria schizopleura gen. et sp. nov., holotype, RGM 962613, sample 2. J-L. Harzhauseria schizopleura gen. et sp. nov., paratype, RGM 962614, sample 2. M-O, R-T. Hydrobiinae sp. indet., RGM 1365350, sample 1. Scale bars: 1 mm (A-O); 100 μm (P-T).