Ulskia ulskii (Clessin & W. Dybowski in W. Dybowski, 1887)

Figs 16, 17

Caspia Ulskii nob.—Clessin & W. Dybowski in W. Dybowski 1887: 38–39.

[ Caspia] Ulskii n. sp. —W. Dybowski 1888: 79, pl. 3, fig. 8a, b.

Pyrgula [(Ulskia)] behningi Logv. et Star. sp. n. — Logvinenko & Starobogatov 1969: 380, fig. 36713).

Pyrgula [(Ulskia)] nana Logv. et Star. sp. n. — Logvinenko & Starobogatov 1969: 379–380, fig. 36712).

Pyrgula [(Ulskia)] ulskii (Cless. et W. Dyb.) — Logvinenko & Starobogatov 1969: 379, fig. 36710).

Pyrgula behningi Logvinenko et Starobogatov, 1968 — Kantor & Sysoev 2006: 97–98, pl. 45, fig. M.

Pyrgula nana Logvinenko et Starobogatov, 1968 — Kantor & Sysoev 2006: 101, pl. 47, fig. D.

Pyrgula ulskii (Clessin et W. Dybowski in W. Dybowski, 1888)— Kantor & Sysoev 2006: 104, pl. 45, fig. F.

Ulskia ulskii (Clessin & W. Dybowski in W. Dybowski, 1887)— Neubauer et al. 2018: 52–54, fig. 5A–K.

Ulskia behningi (Logvinenko & Starobogatov, 1969) — Wesselingh et al. 2019: 72–73.

Ulskia ulskii (Clessin & Dybowski in Dybowski, 1887)— Wesselingh et al. 2019: 73.

Type material. Lectotype (ZB-M W.Dyb. 76) and 33 paralectotypes (ZB-M W.Dyb. 76 and 99) (designated by Anistratenko et al. 2019). The holotype of P. behningi (ZIN #1) and 82 paratypes (ZIN ##2–11) are listed in ZIN systematic catalogue, collected by B.M. Logvinenko in 26/06/1956 – 04/08/1957. As for P. nana, we found a specimen labelled as “ holotype ” in the Starobogatov collection (ZIN), as well as 13 probable paratypes.

Type locality. “Kaspi-See” (Caspian Sea, without further details; Table 1, locality 26). Type locality of P. behningi: Western part of the South Caspian Sea in the vicinity of the Kura River mouth, 120 m (locality 23). The paratypes were collected off Apsheron Peninsula (Azerbaijan) (locality 14). Type locality of P. nana: western part of the Caspian Sea near Apsheron peninsula, 88 m (locality 15); the 13 probable paratypes were retrieved in the eastern part of the South Caspian Sea off Cheleken Peninsula, Turkmenistan (locality 20).

Other material. The “ holotype ” and 6 “ paratypes ” of “ Caspia clessiniolaeformis ”, an unavailable collection name coined by Starobogatov (ZIN, no number), collected in 1957 and 1962 in the eastern part of the Middle Caspi-an Sea at a depth of 56–71 m (localities 5 and 17). Further three specimens labelled by Starobogatov as Caspia ulskii come from locality 17 (ZIN, no number), three from Selitrennoye (locality 1, RGM 1309810, 1309809, 1309856) and five specimens from the Kura delta (localities 25d and 25f, RGM 1310306–1310310) .

Remarks. The characteristic features of Ulskia ulskii are the small (up to 2.15 mm in height, 1.20 mm in width), slender and usually stepped shell with a tightly coiled aperture that rarely leaves an umbilicus (Fig. 16 a–z), a striated–wrinkled protoconch demarcated by a distinct but not particularly bulgy growth rim (Fig. 17 a–o) and a teleoconch microsculpture that consists of tiny, irregular, elongated beads (Fig. 17b, c, f, i, k, m).

Ulskia ulskii is a highly variable species with respect to shell shape. Neubauer et al. (2018) provided a detailed description for material from the Pleistocene of Russia (Fig. 16t, v–z). These specimens are more elongate and slightly larger but otherwise fit well to the lectotype series of U. ulskii . Similarly, Holocene specimens from the Kura delta tend to be more slender and have a less stepped outline (Fig. 16 p–s, u), but the morphological variation is fluent and does not allow establishing clear species boundaries. Rather we consider all these differences to reflect intraspecific variation .

The range of variation also covers the holotype of Pyrgula nana Logvinenko & Starobogatov, 1969 (Fig. 16g, h) and P. behningi Logvinenko & Starobogatov, 1969 (Fig. 16 l–o), which closely resemble some of the paralectotypes of U. ulskii . We thus follow the previous opinion of Neubauer et al. (2018) and consider P. nana a junior synonym of U. ulskii; Pyrgula behningi is a new synonym of U. ulskii .

Furthermore, we found in the ZIN collection of Starobogatov material labelled with the unavailable collection name “ Caspia clessiniolaeformis ”. The “ holotype ” and 6 “ paratypes ” of “ Caspia clessiniolaeformis ” collected in the eastern part of the Middle Caspian Sea fall in the morphological range of U. ulskii (Fig. 16i, j) .

Distribution. Endemic to the Caspian Sea, reported from water depths between 45 and 170 m (Logvinenko & Starobogatov 1969; data of ZIN catalogue). Tarasov (1996b) mentioned the species from 478 m in the South Caspian Basin.