Iraklimelania submediocarinata, 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

Iraklimelania submediocarinata sp. nov.

Etymology.

Named with respect to the keel below the whorl center.

Holotype.

RGM 962689 (Fig. 7K-P ). Babadağ river valley along the Babadağ-Sarayköy road, c. 2.4 km NW of the town of Babadağ, Denizli, Turkey; sample 1 (37°50'40.3"N, 28°52'53.3"E). Kolankaya Formation, Lower Pleistocene, Gelasian.

Additional material.

None (holotype only).

Diagnosis.

Small, slender hydrobiid with distinct, blunt keel below whorl center, slowly growing whorls that show weak subsutural concavity in late ontogeny, small aperture, and sigmoidal growth lines.

Description.

Small, slender hydrobiid shell, with 6 whorls that slowly expand in width and height. Protoconch consisting of c. 1.2 whorls; low domed with broad nucleus, finely-meshed malleate surface with 6-7 widely, but more or less regularly, spaced, weak spiral striae; terminal phase thickened, devoid of surface sculpture; P/T transition indicated by growth stop and onset of growth lines. Distinct, blunt, relatively broad keel develops on about 2nd teleoconch whorl; becomes quickly more pronounced toward 3rd whorl; originally almost in whorl center, keel becomes successively shifted toward lower suture; on last whorl, it is placed between lower third and upper two thirds of whorl height. Keel leaves weak furrow inside shell, at least on last whorl (Fig. 7K ). Disregarding keel, whorls are regularly convex in early whorls, but convexity decreases during ontogeny; whorl portion above keel in last whorl almost straight-sided, with faint concavity below upper suture. Last whorl attains c. 49% of total shell height. Base ~45°, grading from straight-sided upper part into concave neck. Aperture not preserved, but whorl cross-section suggests small, elliptical shape. Growth lines distinct, sigmoidal, with opisthocyrt upper half (above keel) and weakly prosocline lower half (below keel).

Dimensions.

2.83 × 1.13 mm (holotype, RGM 962689; Fig. 7K-P ).

Remarks.

As for the previous species, we consider this one to belong in Iraklimelania . It matches both I. minutissima sp. nov. and the type species in terms of the small, slender shell with convex whorls and narrow subsutural concavity, the small aperture with slight bulge and the sigmoidal growth lines. The main difference to both species is the blunt keel below the center of the whorls. This feature reminds of? Iraklimelania coa , which differs however in the distinctly conical shell with nearly straight-sided whorls.

Distribution.

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

Subfamily Hydrobiinae Stimpson, 1865

Figures

Figure 7. Caspiinae (Hydrobiidae) of the Kolankaya I fauna. A-E. Iraklimelania minutissima sp. nov., holotype, RGM 962618, sample 2. F-J. Iraklimelania minutissima sp. nov., juvenile or subadult form, SNSB-BSPG 2023 XII 5, sample 2. K-P. Iraklimelania submediocarinata sp. nov., holotype, RGM 962689, sample 1. Scale bars: 1 mm (A-D, F-I, K-N); 100 μm (E, J, O, P).