Turricaspia meneghiniana (Issel, 1865)

Neubauer, Thomas A., Velde, Sabrina van de, Yanina, Tamara & Wesselingh, Frank P., 2018, A late Pleistocene gastropod fauna from the northern Caspian Sea with implications for Pontocaspian gastropod taxonomy, ZooKeys 770, pp. 43-103 : 43

Turricaspia meneghiniana (Issel, 1865) Fig. 13A-K

Turricaspia meneghiniana *1865 Bythinia Meneghiniana, Issel; Issel: 21, pl. 1, figs 12-13.

Turricaspia meneghiniana 1866 Bythinia Meneghiniana, Issel. - Issel: 405, pl. 1, figs 12-13.

Turricaspia meneghiniana 1917 Micromelania (Turricaspia) caspia Eichw. var. inflata nov. var. - B. Dybowski & Grochmalicki: 9, pl. 1, fig. 5.

Turricaspia meneghiniana ? 1969 Pyrgula caspia (Eichw). - Logvinenko & Starobogatov: 369-370, fig. 364 (1).

Turricaspia meneghiniana ? 1969 Pyrgula meneghiniana (Issel). - Logvinenko & Starobogatov: 370, fig. 365 (2).

Turricaspia meneghiniana non 1987 T. [urricaspia] meneghiniana meneghiniana (Iss.). - Alexenko & Starobogatov: 35, fig. 8.

Turricaspia meneghiniana 2006 Turricaspia meneghiniana (Issel, 1865). - Kantor & Sysoev: 109, pl. 49, fig. E.

Turricaspia meneghiniana 2016 Turricaspia meneghiniana (Issel, 1865). - Vinarski & Kantor: 248.

Material.

248 specimens ( RGM 1309799 , RGM 1309800 , RGM 1310197 , RGM 1310198 , RGM 1310256 , LV 201518 ) .

Type material.

Not traced.

Type locality.

"Nei giacimenti fossiliferi di Baku" (from fossil deposits in Baku).

Dimensions.

10.86 × 4.27 mm ( RGM 1310256, Fig. 13A-C ); 10.91 × 4.36 mm ( LV 201518, Fig. 13D, E, I ); 11.17 × 4.50 mm ( RGM 1310197, Fig. 13F-H ); 10.82 × 4.14 mm; 11.23 × 4.40 mm; 11.65 × 4.49 mm.

Description.

Conical shell with up to 9.3 whorls. Protoconch comprises 1.3 whorls, measuring 440 µm in diameter, with slightly inflated initial part; nucleus measures 150 µm in diameter; entire protoconch surface weakly granulate; indistinct spiral striae appear on second half; P/T transition distinct, formed by sharp, thin axial line. Teleoconch whorls increase slowly but regularly in height and width; whorls moderately convex, whereas convexity slightly decreases with ontogeny. Last whorl attains 45-48% of shell height, passes over perfect convexity into slightly convex base. Aperture ovoid, inclined, closely attached to base of preceding whorl across almost entire parietal margin. Peristome thin, not thickened, little expanded; weakly sigmoidal in lateral view, with broad, shallow indentation in upper half and broad, weak protrusion in lower half; inner lip protrudes in lateral view, extending sheet-like over base of penultimate whorl; umbilicus very narrow, slit-like. Growth lines weakly sigmoidal: strongly prosocline in upper half, weakly opisthocline in lower half. Several specimens show faint spiral threads on last and penultimate whorls.

Discussion.

Our material matches well to the description of Issel (1865), corresponding in the conical shell shape, the regularly increasing whorls, the rounded last whorl with faint spiral striae, and the ovate, adapically angulated aperture; only his specimens (13.5 × 5 mm) are larger than ours and consist of more whorls. Compared to his description, Issel’s illustration seem to overemphasize the relative height of the last whorl and underrepresent the pronounced whorl convexity. However, variability as to these characteristics is discernible also in our material.

Micromelania subulata Westerlund, 1902 is commonly listed as junior synonym of this species but always without discussion (e.g., Logvinenko and Starobogatov 1969, Kantor and Sysoev 2006, Vinarski and Kantor 2016). Westerlund’s (1902b) description refers to a large (15 mm), elongate shell with 9.5-10 whorls and a thickened callus connecting the peristome margins. These features partly oppose Issel’s description, which is why we tend to consider both taxa as separate, in contrast to most previous authors. Unfortunately, Westerlund’s (1902b) type material of this species could not be traced, neither in the Göteborg Natural History Museum nor the Swedish Museum of Natural History in Stockholm, where the largest part of Westerlund’s material is stored ( Vinarski et al. 2013).

Another commonly cited synonym is Micromelania caspia var. inflata B. Dybowski & Grochmalicki, 1915, which indeed matches both Issel’s description and our material.

Turricaspia meneghiniana differs from the similarly large Laevicaspia caspia (Eichwald, 1838) in its regularly conical profile, the higher number of whorls, and the higher whorl convexity. The drawings of " Pyrgula meneghiniana (Issel)" provided by Logvinenko and Starobogatov (1969) indicate a broader shell with low whorl convexity and might represent a different species. In contrast, Pyrgula caspia sensu Logvinenko and Starobogatov (1969) (non Eichwald 1838) resembles the present species in terms of the high shell convexity and regular growth rate and might be conspecific. Turricaspia meneghiniana sensu Alexenko and Starobogatov (1987), with few, low convex whorls and an angled base, is clearly a different species.

Distribution.

Endemic to the Caspian Sea, reported from middle and south Caspian Sea at depths between 0 and 35 m ( Logvinenko and Starobogatov 1969).

Figures

Figure 13. Pyrgulinae. A-C Turricaspia meneghiniana (Issel, 1865), RGM 1310256 D, E, I T. meneghiniana, LV 201518 F-H T. meneghiniana, RGM 1310197 J, K T. meneghiniana, RGM 1309799.