Laevicaspia caspia (Eichwald, 1838)

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 caspia (Eichwald, 1838) Fig. 8A-K

Laevicaspia caspia *1838 Rissoa caspia m.; Eichwald: 154-155.

Laevicaspia caspia 1841 Rissoa caspia - Eichwald: 256-257, pl. 38, figs 14-15.

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

Laevicaspia caspia non 1876 Hydrobia caspia , Eichw. - Grimm: 150-153, pl. 6, fig. 15.

Laevicaspia caspia non 1877 Hydrobia caspia , Eichw. - Grimm: 79-80, pl. 7, figs 3a-d.

Laevicaspia caspia non 1887 Micromelania caspia Eichw. sp. - W. Dybowski: 21.

Laevicaspia caspia non 1888 Micr. [omelania] caspia Eichw. sp. - W. Dybowski: 78, pl. 1, fig. 1.

Laevicaspia caspia ? 1896 B. [uliminus] (Napaeus?) goebeli Westerlund: 188.

Laevicaspia caspia 1914 Micromelania (?) Micromelania curta Nalivkin: 21-22, 31, pl. 6, figs 1-2 [partim; non figs 3-4, 7, 9-14].

Laevicaspia caspia 1914 [ Micromelania (?) Micromelania curta ] var. Micromelania curta plano-convexa Nalivkin: 22, 31, pl. 6, figs 15-18.

Laevicaspia caspia non 1914 Micromelania caspia Eichw. - Nalivkin: 22, 31, pl. 6, figs 5-6 [partim; non fig. 8].

Laevicaspia caspia non 1917 Micromelania ( Turricaspia , Laevicaspia ) Laevicaspia caspia Eichw. - B. Dybowski & Grochmalicki: 5-8, 36-38, pl. 1, figs 1-3.

Laevicaspia caspia non 1969 Pyrgula caspia (Eichw.). - Logvinenko & Starobogatov: 369-370, fig. 364 (1).

Laevicaspia caspia 1987 T. [urricaspia] caspia (Eichw.). - Alexenko & Starobogatov: 33, fig. 2.

Laevicaspia caspia 2006 Turricaspia caspia (Eichwald, 1838). - Kantor & Sysoev: 106, pl. 49, fig. M.

Laevicaspia caspia 2014 Euxinipyrgula lincta . - Taviani et al.: 4, fig. 3c [non Micromelania lincta Milashevich, 1908].

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

Material.

300 specimens ( RGM 1309788 , RGM 1309789 , 1309797, RGM 1309798 , RGM 1310196 , RGM 1310257 , RGM 1310258 , LV 201511 ) .

Type material.

Lectotype: ZIN (No. 1 in systematic catalogue), designated by Alexenko and Starobogatov (1987).

Type locality.

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

Dimensions.

9.01 × 3.31 mm ( RGM 1310257, Fig. 8A-C ); 7.88 × 3.31 mm ( RGM 1310258, Fig. 8D-F ); 10.33 × 3.92 mm ( LV 201511, Fig. 8I-K ); 9.92 × 3.83 mm; 10.21 × 3.88 mm; 9.52 × 3.54 mm; 9.69 × 3.61 mm.

Description.

Large, slender ovoid shell comprising up to 8.3 whorls. Protoconch large, measuring 535-600 µm at 1.15-1.2 whorls, with initial part inflated; nucleus almost immersed, 190-230 µm wide; nucleus and early protoconch bear intentions of malleate sculpture, which passes into granular surface after half a whorl accompanied by onset of spiral striae; P/T boundary indistinct. Whorl convexity decreasing rapidly: first teleoconch whorl moderately convex, second to last whorl low convex, sometimes almost straight-sided; maximum convexity is in lower half; whorls closely attached, suture narrow; a very small but marked convexity appears at upper suture, producing a faintly stepped spire; occasionally, it is accompanied by shallow abapical concavity. Last whorl makes up 46-50% of shell height, passing over regular but weakly convex to near straight-sided to slightly concave base. Aperture slender ovoid, inclined, closely attached to preceding whorl; in latest ontogeny, shell growth is more abapically directed, resulting in marked thickening at adapical tip. Peristome simple, thin, slightly expanded and indented at base; distinctly and regularly sigmoidal in lateral view, with upper half broadly indented and lower half broadly protruding; inner lip protrudes in lateral view, extending sheet-like over base of penultimate whorl; umbilicus mostly closed, rarely 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.

Different concepts of this species previously applied have led to considerable confusion about its real identity. This is partly rooted in the description and illustration provided by Eichwald (1838, 1841) that were insufficient to allow safe discrimination from similar species. For instance, Micromelania caspia sensu Grimm (1876, 1877), W. Dybowski (1887-1888) and B. Dybowski and Grochmalicki (1917) differs from the present species in the acute apex, the moderately convex whorls, the deep suture and the thin peristome. As already noted by Alexenko and Starobogatov (1987), it represents a different species, i.e., Laevicaspia lincta (Milashevich, 1908). That species was described from Lake Katlabukh near the Danube delta in Ukraine (lectotype, which matches Milashevich’s description, is illustrated in Kantor and Sysoev 2006: 95, pl. 45, fig. D; as Euxinipyrgula lincta ). Specimens from the Neoeuxinian (late Pleistocene) of the Marmara Sea identified as E. cf. lincta by Taviani et al. (2014) differ from that species in the near straight-sided whorls and thickened peristome; in fact, the material corresponds well to L. caspia .

Micromelania caspia sensu Nalivkin (1914) comprises at least two species, both being more elongate, having more whorls and relatively smaller last whorls than L. caspia . In turn, some of the illustrated syntypes of " Micromelania " Pyrgula curta Nalivkin, 1914 and the variety " Micromelania " Micromelania curta var. planoconvexa Nalivkin, 1914 from Bakunian deposits of Shikhovo, Apsheron Peninsula, Azerbaijan, closely resemble the present species and are thus (partly) considered synonymous. " Micromelania " Micromelania curta encompasses a great variability of shapes, ranging from slender, elongate ( Micromelania caspia - type) to broad, conical shells. Since no holotype or lectotype have been designated, the status of this species is unresolved at present. Note that Pyrgula curta sensu Logvinenko and Starobogatov (1969) and Kantor and Sysoev (2006) does not correspond to Nalivkin’s species but rather to the specimens Nalivkin (1914) misidentified as Micromelania caspia .

Similarly, Pyrgula caspia sensu Logvinenko and Starobogatov (1969) is a quite different species, showing highly convex whorls and an inflated last whorl. It rather ranges within the morphological variability of Turricaspia meneghiniana (see below).

Alexenko and Starobogatov (1987) finally brought stability to the identity of L. caspia by designating a lectotype (see Kantor and Sysoev 2006: 106, pl. 49, fig. A; as Turricaspia caspia ), which matches well our specimens. The label accompanying their specimen reads "Kaspiyskoye more" ("Caspian Sea"), which differs from the information provided by Eichwald (Dagestan) (see also discussion in Vinarski and Kantor 2016: 246). Inspection of the catalogue of the Zoological Institute, Russian Academy of Sciences, St. Petersburg ( ZIN), however, confirmed that the lectotype is based on Eichwald’s original material.

The similar Laevicaspia iljinae (Golikov & Starobogatov, 1966) from Holocene deposits of the Crimean Peninsula can be distinguished in its more slender shape and the spruce-like whorl outline (i.e., steep, straight-sided upper two-thirds passing over convexity into flatter, convex lower third; see also Kantor and Sysoev 2006: 108, pl. 49, fig. D).

Distribution.

Endemic to the Caspian Sea ( Logvinenko and Starobogatov 1969 stated that the species occurs at a depth of 30-150 m in the middle and southern Caspian Sea, but these data have to be revised given their incorrect concept of L. caspia ).

Figures

Figure 8. Pyrgulinae. A-C Laevicaspia caspia (Eichwald, 1838), RGM 1310257 D-F L. caspia, RGM 1310258 G L. caspia, RGM 1310197 H L. caspia, RGM 1310198 I-K L. caspia, LV 201511.