Laevicaspia conus (Eichwald, 1838) 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 conus (Eichwald, 1838) comb. n. Fig. 9I-P

Laevicaspia conus *1838 Rissoa Conus m.; Eichwald: 155.

Laevicaspia conus 1841 Rissoa Conus m. - Eichwald: 257, pl. 38, figs 16a-b [wrongly given as "figs 16-17" on p. 257; see also corrigendum at the end of Eichwald’s work].

Laevicaspia conus 1853 Riss. [oa] conus m. - Eichwald: 273.

Laevicaspia conus non 1876 Eulima conus , Eichw?. - Grimm: 154-156, pl. 6, fig. 14.

Laevicaspia conus 1887 Nematurella conus Eichw. sp. (non Grimm). - W. Dybowski: 45.

Laevicaspia conus 1888 [ Nematurella ] Nematurella conus Eichw. sp. - W. Dybowski: 78, pl. 2, fig. 3.

Laevicaspia conus ? 1896 Prosostenia [sic] Prosostenia conus Eichw. - Sinzov: 49-50, pl. 1, figs 30-33.

Laevicaspia conus 1926? Nematurella conus (Eichwald). - Wenz: 2007.

Laevicaspia conus 1952 Caspiella conus (Eichwald, 1841). - Zhadin: 259, fig. 211.

Laevicaspia conus 1969 Pyrgula [( Caspiella )] Pyrgula conus (Eichw). - Logvinenko & Starobogatov: 374, fig. 366 (5-6).

Laevicaspia conus non 2006 Turricaspia conus conus (Eichwald, 1838). - Kantor & Sysoev: 106, pl. 48, fig. J.

Laevicaspia conus 2016 Turricaspia conus conus (Eichwald, 1838). - Vinarski & Kantor: 246-247.

Material.

1135 specimens ( RGM 1309828 , RGM 1309829 , RGM 1309830 , RGM 1310199 , RGM 1310226 -1310228, LV 201515 ) .

Type material.

Not traced.

Type locality.

"In eodem lapide calcareo, fossilis" (in the same limestone [referring to previous species, found in Dagestan], fossil).

Dimensions.

5.14 × 2.19 mm ( RGM 1309830, Fig. 9I, J ); 4.60 × 2.18 mm ( LV 201515, Fig. 9K ); 4.02 × 1.91 mm ( RGM 1309829, Fig. 9L-O ); 3.87 × 1.87 mm ( RGM 1309828, Fig. 9P ); 4.60 × 2.23 mm ( RGM 1310226); 5.12 × 2.37 mm ( RGM 1310227); 4.17 × 2.14 mm ( RGM 1310228).

Description.

Ovoid, glossy shell with up to 6.8 whorls. Shell outline variable, depending on growth stage: shells with up to 5 whorls are rather broad, nearly conical; in late ontogeny, shell growth is directed adapically, producing more elongate shapes with narrow, high last whorl; sometimes, these slender elongate morphotypes have slightly irregular shape. Protoconch consists of 1.2 whorls with 355 µm in diameter; nucleus almost immersed, 125 µm wide; surface faintly malleate or granulate, with intentions of spiral sculpture detected in some specimens; P/T boundary very distinct, marked by sharp, thin axial line. Teleoconch whorls weakly to moderately convex, sometimes adapically flattened. Last whorl attains between 55-63% of total height, grades into straight-sided or weakly convex base. Aperture drop-shaped, inclined, closely attached to base of preceding whorl, usually covering or rarely leaving slit-like umbilicus. Peristome slightly expanded, thin or thickened all around, especially at adapical tip; regularly sinuate in lateral view, with broad adapical indentation and about equally broad and high abapical protrusion. Growth lines weak, prosocline in upper half, orthocline in lower half.

Discussion.

Logvinenko and Starobogatov (1969) listed " Rissoa conus Eichwald, 1841, partim" in synonymy of Pyrgula kolesnikoviana Logvinenko & Starobogatov in Golikov & Starobogatov, 1966 (now classified in Laevicaspia ; see below), but without any explanation. The synonymy list was expanded as " Rissoa conus sensu Eichwald, 1841, partim, non Eichwald, 1838" by Kantor and Sysoev (2006) and Vinarski and Kantor (2016), yet again without discussion. The synonymy is not mentioned in the original description of Laevicaspia kolesnikoviana in Golikov and Starobogatov (1966). Very likely, the synonymy roots in the ambiguous description of Eichwald (1838, 1841), summarizing two different morphologies. Eichwald referred to the typical form as having a conical shell with seven, gently increasing whorls, whereas the last two are much broader; the size was indicated as 2 × 1 lin., which corresponds to 4.2 × 2.1 mm (given Eichwald used the Russian liniya). In addition, he mentioned rarer, slightly longer (3 lin.) specimens, with deeper suture and straight-sided whorls. In 1841, Eichwald illustrated one of these rare specimens. The description in the 1841-work, however, is almost identical to the original description. In this light, it remains unclear why Kantor and Sysoev (2006) and Vinarski and Kantor (2016) referred to as " Rissoa conus sensu Eichwald, 1841, partim, non Eichwald, 1838" in their synonymy lists of L. kolesnikoviana . To complete confusion, the specimen illustrated in Kantor and Sysoev (2006) is not L. conus , differing in the broad, blunt apex and the near straight-sided whorls; it rather resembles L. kowalewskii (Clessin & W. Dybowski in W. Dybowski, 1887).

The holotype of L. kolesnikoviana illustrated by Kantor and Sysoev (2006, pl. 47, fig. N) corresponds to the description and illustration of the rare, slender morphology of Laevicaspia conus sensu Eichwald in terms of the number of whorls and the near straight-sided whorls; it differs only in the considerably smaller size (3.7 mm vs. 6.3 mm). Yet, Golikov and Starobogatov (1966) and Logvinenko and Starobogatov (1969) indicate larger sizes for L. kolesnikoviana (5.5 mm and 6.5 mm, respectively), suggesting a great variability in size. On the other hand, the two morphologies delineated by Eichwald also match our own observations on L. conus . In late ontogeny, growth is directed almost entirely abapically, resulting in more elongate shells with an additional whorl. These larger morphologies correspond completely to the smaller, relatively bulkier shells in all other aspects, which is why we consider them as morphotypes rather than species-group taxa. Without Eichwald’s material at hand it is difficult to arrive at a conclusion on this matter.

The species has affinities with several representatives of the Azov and Black seas. Pyrgula (Caspiella) lindholmiana Golikov & Starobogatov, 1966, today considered as a subspecies of L. conus (e.g., Vinarski and Kantor 2016), has a larger and broader shell. Similarly, Laevicaspia milachevitchi (Golikov & Starobogatov, 1966) and Laevicaspia boltovskoji (Golikov & Starobogatov, 1966) are broader than L. conus , while Laevicaspia lincta (Milashevich, 1908) and Laevicaspia limanica (Golikov & Starobogatov, 1966) are more slender and larger.

" Eulima conus Eichwald" as described and illustrated by Grimm (1876, 1877) has little resemblance to actual L. conus . He illustrated a very elongate, conical shell with many more and almost perfectly straight-sided whorls. This fact was already noticed by Clessin and W. Dybowski a few years later, and they introduced Micromelania grimmi Clessin & W. Dybowski in W. Dybowski, 1887 for the misidentified species.

The illustrations of specimens from the Kuyalnikian (late Pliocene to early Pleistocene) of the Odessa region identified as Prososthenia conus by Sinzov (1896) show shells with similar shape, proportions and whorl convexity. A more detailed examination of material from the region is required to assess whether it is indeed conspecific with L. conus .

Distribution.

Endemic to the Caspian Sea, reported from depths between 0 and 120 m ( Logvinenko and Starobogatov 1969).

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.