Laevicaspia cincta (Abich, 1859) Neubauer & Velde & Yanina & Wesselingh, 2018

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

Laevicaspia cincta (Abich, 1859) comb. n. Fig. 9A-H

Laevicaspia cincta *1859 Rissoa cincta ; Abich: 57, pl. 2, fig. 6.

Laevicaspia cincta ?1887 Caspia Orthii Clessin & W. Dybowski in W. Dybowski: 40.

Laevicaspia cincta ?1888 [ Caspia ] Orthii n. sp. - W. Dybowski: 79, pl. 3, fig. 6.

Laevicaspia cincta 1969 Pyrgula [( Caspiella )] Pyrgula cincta (Abich). - Logvinenko & Starobogatov: 372, fig. 366 (4).

Laevicaspia cincta 2006 Pyrgula cincta (Abich, 1859). - Kantor & Sysoev: 98, pl. 47, fig. L.

Laevicaspia cincta 2016 Pyrgula cincta (Abich, 1859). - Vinarski & Kantor: 236.

Material.

174 specimens ( RGM 1309806 , RGM 1309807 , RGM 1310200 , LV 201514 ) .

Type material.

Not traced.

Type locality.

Abich (1859) specified the type locality on p. 12-13 as "Gulf of Baku".

Dimensions.

3.83 × 1.93 mm ( LV 201514, Fig. 9A, B ); 4.05 × 1.89 mm ( RGM 1309807, Fig. 9C-E ); 4.41 × 2.10 mm ( RGM 1309806, Fig. 9F-H ); 4.73 × 2.11 mm; 4.59 × 2.10 mm; 4.58 × 2.17 mm.

Description.

Slender ovoid shell with up to 6.5 whorls. Protoconch broad, low dome-shaped, consists of 1.2 whorls that measure 415 µm in diameter, with slightly inflated initial part; nucleus 150 µm wide; protoconch surface weakly granulate, with intentions of striae on second half; P/T transition distinct, formed by sharp, thin axial line. Whorl convexity decreases steadily during ontogeny, with early teleoconch whorls being moderately convex and penultimate and last whorl low convex to almost straight-sided. On third teleoconch whorl, weak subsutural band emerges that slightly enhances during ontogeny; band forms weak bulge throughout, with maximum convexity in its lower half and steep, almost straight-sided ramp in upper half; abapical demarcation clear, sometimes accompanied by thin groove. Last whorl attains 54-65% of shell height, passing from flattened whorl flank over marked convexity into steep, straight-sided base. Aperture near drop-shaped, inclined, with acute adapical angle, straight parietal margin, obtuse angle between parietal and columellar margins, sometimes slightly expanded palatal margin. Peristome not thickened, weakly expanded at columella and base; regularly sinuate in lateral view, with broad adapical indentation and about equally broad and high abapical protrusion. Umbilicus closed or very narrow. Growth lines weakly prosocline in upper half, near orthocline in lower half.

Discussion.

The Selitrennoye specimens match with the original description in terms of size (shell height: 3-4 mm), the ovoid shell shape, the number of whorls, the rounded last whorl and the simple peristome margin; they differ in the expression of the subsutural band, which Abich indicated to be "weakly keeled". We consider these differences to range within the intraspecific variability of this species.

Laevicaspia cincta can be readily distinguished from other Pontocaspian Pyrgulinae by its ovoid, slightly stepped shell with broad, blunt apex, subsutural band and flattened whorls in later ontogeny. Laevicaspia abichi (Logvinenko & Starobogatov, 1969) from the middle Caspian Sea, differs in the much larger size (6.8 × 3 mm), the conical shape, the narrower subsutural band and the larger aperture. The Caspian endemic species Laevicaspia kowalewskii (Clessin & W. Dybowski in W. Dybowski, 1887) resembles L. cincta very closely in terms of the slender ovoid shape with near straight-sided whorls, the closely attached aperture with thin peristome, and the lacking umbilicus; it differs in the lack of a subsutural band and the more elongate shape.

Caspia orthii Clessin & W. Dybowski in W. Dybowski, 1887 was synonymized with the present species by previous authors (e.g., Logvinenko and Starobogatov 1969, Kantor and Sysoev 2006, Vinarski and Kantor 2016). The original description matches well our specimens in terms of size (4.8 × 1.9 mm), number of whorls, expression of the subsutural band and shape of the aperture; the only difference is the “elongated-conical” shape compared to the ovoid shells of L. cincta described by Abich (1859) and represent by our material. Although not having seen W. Dybowski’s type material, we tentatively follow the previous assessment and consider Caspia orthii a junior synonym of Laevicaspia cincta .

Note that Rissoa cincta Deshayes, 1861 (p. 404, pl. 24, figs 4-6), described from the Eocene (Bartonian) of the Paris Basin, is a junior primary homonym of this species and thus invalid. At present, this species is classified in the genus Pseudotaphrus Cossmann, 1888 ( Ponder 1984: 96).

Distribution.

Endemic to the Caspian Sea, in the southern part at a depth of> 250 m ( Parr et al. 2007).

Figures

Figure 9. Pyrgulinae. A, B Laevicaspia cincta (Abich, 1859), LV 201514 C-E L. cincta, RGM 1309807 F-H L. cincta, RGM 1309806 I, J L. cincta, RGM 1309830 K Laevicaspia conus (Eichwald, 1838), LV 201515 L-O L. conus, RGM 1309829 P L. conus, RGM 1309828.