Aplexa cf. subhypnorum Gottschick, 1920

Harzhauser, Mathias, Neubauer, Thomas A. & Hoşgör, İzzet, 2018, Oligocene-Miocene freshwater gastropods from the Oltu-Narman Basin in eastern Turkey, Acta Palaeontologica Polonica 63 (2), pp. 357-369 : 364

Aplexa cf. subhypnorum Gottschick, 1920

Fig. 5A, B .

cf. 1920 Aplexa subhypnorum n. sp.; Gottschick 1920: 116, pl. 2: 9.

Material.—Five fragmentary specimens: NHMW 2018 / 0019/0020, largest specimen ( Fig. 5A ) ; NHMW 2018 /0019/ 0021 ( Fig. 5B ) ; NHMW 2018 /0019/0021 (3 specimens) from the upper Susuz Formation ( upper Oligocene or lower Miocene ) at Kömürlü, Oltu-Narman Basin, northeastern Turkey .

Description.—Sinistrally coiled shell with high conical spire ( Table 4) of at least three high, moderately convex teleoconch whorls (protoconch and early teleoconch not preserved). Last whorl high, moderately convex; suture deeply incised. Shell surface of spire whorls consisting of prominent, broad, densely spaced axial riblets becoming much weaker on last whorl. Axial sculpture continues on narrow subsutural cord. Aperture attaining about 50% of total height, angulated in posterior tip. Outer lip thin; inner lip delicate, narrow; columella weakly concave.

Remarks.—All specimens are deformed due to sediment compaction and only fragmentarily preserved. The high and slender spire suggests a placement in Aplexa Fleming, 1820 rather than in Physa Draparnaud, 1801 . Aplexa is poorly known from the Oligocene and Miocene of Europe and Turkey. So far, only Aplexa subhypnorum Gottschick, 1920 was described from the middle Miocene of Steinheim in southern Germany ( Gottschick 1920). Juvenile specimens of Aplexa were also documented from the middle Miocene of Opole in Poland ( Harzhauser and Neubauer 2018) and the late Miocene of the Vienna Basin ( Harzhauser and Binder 2004). The Turkish shells largely match the description of Aplexa subhypnorum by Gottschick (1920) and agree in size and sculpture. The illustrations by Gottschick (1920), however, are too sketchy to support the identification of the poorly preserved Turkish material. Moreover, the large biogeographic and stratigraphic distance between the German and Turkish occurrences may give rise to doubts whether both are conspecific. Unfortunately, the syntypes of Aplexa subhypnorum are lost ( Salvador et al. 2016), and a direct comparison is impossible.

Aplexa subhypnorum is known from the middle Miocene of southern Germany. It might have also occurred at that time in Poland and during the late Miocene in the Vienna Basin ( Harzhauser and Neubauer 2018).

Figures

Fig. 5. Physid (A, B) and planorbid (C–I) gastropods from upper Oligocene–lower Miocene Susuz Formation, Kömürlü, Turkey. A, B. Aplexa cf. subhypnorum Gottschick, 1920. A. NHMW 2018/0019/0020, in dorsal (A1) and apertural (A2) views; detail of sculpture (A3). B. NHMW 2018/0019/0021, in apertural view. C–E. Planorbarius cf. cornu (Brongniart, 1810). C. NHMW 2018/0019/0022, in apical view, specimen with characteristic protoconch microsculpture; C1 detail of C2. D. NHMW 2018/0019/0023, in apical view, specimen with prominent spiral cords. E. NHMW 2018/0019/0024, in lateral view. F–I. Gyraulus sp. F. NHMW 2018/0019/0025, in umbilical (F1), apical (F2), and lateral (F3) views. G. NHMW 2018/0019/0026, in umbilical (G1), apical (G2), and lateral (G3) views. H. NHMW 2018/0019/0027, in umbilical (H1) and apical (F2) views. I. NHMW 2018/0019/0028, in lateral view. Scale bars A1, A2, B, 5 mm; C1, 200 μm; A3, C2, D, E, 1 mm, F–I, 500 μm.