Falsipyrgula? coronata, 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

Falsipyrgula? coronata sp. nov.

Etymology.

The species epithet means “crowned” in Latin and refers to the beaded keel.

Holotype.

RGM 1310837 (Fig. 12A-C ). 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 962611 (Fig. 12J-L ) from sample 2; SNSB-BSPG 2023 XII 18 (Fig. 12D-F, T ) from sample 2; SNSB-BSPG 2023 XII 19 (Fig. 12I ) from sample 3.

Additional material.

Sample 2: 1 specimen (RGM 1310377), 27 partly incomplete specimens and 10 fragments (RGM 1310858); sample 3: 4 specimens and 2 fragments (RGM 1310859).

Diagnosis.

Conical pyrguline shell characterized by central to subcentral, typically beaded keel, topped by shallow, straight-sided subsutural whorl profile, convex portion below keel, grading into straight-sided base, thin peristome, and narrow umbilicus.

Description.

Moderately sized conical shell with up to 6 whorls. Protoconch poorly preserved in all studied specimens; surface and P/T boundary unknown. Already on approximately first to second teleoconch whorl a central to subcentral keel appears, which increases continuously in strength through ontogeny. Also in cases with early keel placed at whorl center, keel becomes distinctly subcentral in later ontogeny. Keel typically bears nodules (Fig. 12D-F ), which are sometimes not visible, probably due to abrasion (Fig. 12A-C, I-L ). Whorl portions above and below keel straight-sided. Last whorl attains ~68-71% (n = 3) of total shell height; passes over weak convexity into moderately steep (~45°), straight-sided base. Aperture broadly ovoid, with rather thin peristome and adnate inner lip; umbilicus narrow.

Dimensions.

7.82 × 5.26 mm (holotype, RGM 1310837; Fig. 12A-C ), 10.02 × 6.35 mm (paratype, RGM 962611; Fig. 12J-L ), 6.73 × 3.78 mm (paratype, SNSB-BSPG 2023 XII 19; Fig. 12I ), 4.05 × 2.84 mm (paratype, juvenile, SNSB-BSPG 2023 XII 18; Fig. 12D-F, T ).

Remarks.

As for other members in the Staja - Falsipyrgula species complex, the shell of this species exhibits a certain degree of variability. Occasionally, species with a more slender shell (Fig. 12I ) or a narrower, non-beaded keel (Fig. 12J-L ) are observed. The latter feature may, however, be the result of poor preservation, in many cases shell surfaces and sculptural elements are abraded. Common to all specimens is the conical shell, the comparatively shallow and straight-sided whorl profile above the keel, the thin and edgy peristome, and the narrow umbilicus. These features distinguish Falsipyrgula? coronata sp. nov. from similar species of Falsipyrgula , including the co-occurring F. cf. sieversi . The latter species shares the beaded keel, which is, however, consistently weaker and slightly lower positioned on the whorl, but the shell is ovoid, smaller, and has a stronger inclined, regularly ovoid aperture. Extant Falsipyrgula species have a lower positioned keel or multiple keels or otherwise differ in shape ( Schütt and Yildirim 1999).

Prososthenia attica Fuchs, 1877 sensu Schütt and Besenecker (1973, pl. 1, fig. 7) from the Late Miocene (?) of Chios resembles F.? coronata in terms of overall shell shape and presence of a subcentral keel, but the last whorl is tapered and the whorl profile above the keel is convex. Original P. attica from the Pliocene of Megara is more elongate and has only a week keel near the whorl base ( Fuchs 1877) and is probably a different species as the Chios specimens.

Distribution.

Known only from the Early Pleistocene of the Denizli Basin.

Figures

Figure 12. The Staja - Falsipyrgula species complex of the Kolankaya I fauna. A-C. Falsipyrgula? coronata sp. nov., holotype, RGM 1310837, sample 2. D-F, T. F.? coronata sp. nov., SNSB-BSPG 2023 XII 18, sample 2. G, H. Falsipyrgula cf. sieversi (Boettger, 1881), RGM 1310376, sample 2. I. F.? coronata sp. nov., SNSB-BSPG 2023 XII 19, sample 3. J-L. F.? coronata sp. nov., RGM 962611, sample 2. M-O, U. F. cf. sieversi, RGM 962610, sample 2. P-R. F. cf. sieversi, SNSB-BSPG 2023 XII 20, sample 2. S. F.? coronata sp. nov., RGM 1310377, sample 2. Scale bars: 1 mm (A-R); 100 μm (S-U).