Andrusovia brusinai Starobogatov, 2000

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

Andrusovia brusinai Starobogatov, 2000 Fig. 6F-K, M-N

Andrusovia brusinai *2000 Andrusovia brusinai Starobogatov, sp. nov.; Starobogatov: 41, fig. 1C.

Andrusovia brusinai 2006 Andrusovia brusinai Starobogatov, 2000. - Kantor & Sysoev: 83, pl. 40, fig. C.

Andrusovia brusinai 2016 Andrusovia brusinai Starobogatov, 2000. - Vinarski & Kantor: 214.

Material.

39 specimens ( RGM 1309839 , RGM 1309840 , RGM 1310206 , LV 201509 ) .

Type material.

Holotype: ZIN (no number).

Type locality.

Eastern part of the middle Caspian Sea (42°42.5'N, 51°32.5'E, WGS 84), at 80 m.

Dimensions.

1.52 × 1.44 mm ( RGM 1309840, Fig. 6F, G ); 1.54 × 1.55 mm ( LV 201509, Fig. 6H, K, N ); 1.81 × 1.80 mm ( RGM 1309839, Fig. 6I, J, M ); 1.71 × 1.52 mm; 1.67 × 1.69 mm; 1.83 × 1.55 mm; 1.64 × 1.51 mm.

Description.

Shell broad trochiform, about as high as wide, with up to 4 whorls. Rarely specimens with slightly elevated spire occur. Protoconch high domical, about semicircular in profile; initial part immersed; consists of 1.1 whorls, measures 300 µm in diameter; nucleus about 90 µm wide; protoconch surface finely but strongly malleate near lower suture, rest appears to be irregularly granulate, but that might be due to poor preservation; P/T boundary sharp, marked by massive growth constrictions near lower suture. Teleoconch whorls highly convex, with maximum convexity in adapical half, producing slightly stepped spire. Last whorl attains 74-81% of shell height. Aperture broadly drop-shaped, slightly inclined, with faint adapical notch at contact to penultimate whorl. Peristome slightly thickened and expanded at columella and base; sinuate in lateral view, with weakly protruding central part and weak adapical indentation. Umbilicus wide, deep. Fine prosocline growth lines cover shell. On one specimen, traces of spiral threads occur on base.

Discussion.

The Caspian congeners Andrusovia dybowskii Brusina in Westerlund, 1902a (sensu Starobogatov 2000) and A. andrusovi Starobogatov, 2000 differ from the present species in their much lower spires. Andrusovia marina (Logvinenko & Starobogatov, 1969) is smaller and has a shorter spire. Starobogatov (2000) based the distinction from A. brusinai on minor differences in shell ratios but these are strongly affected by the varying number of whorls and shell size; it might well be that A. marina and A. brusinai are just different growth stages of the same species. Since we have not seen the type material of Logvinenko and Starobogatov (1969), we tentatively accept the distinction of both taxa by Starobogatov (2000). Further comparison with the Logvinenko and Starobogatov material is essential to assess whether the two names refer indeed to distinct species.

Andrusovia brusinai resembles several recent species of Horatia Bourguignat, 1887, Hauffenia Pollonera, 1898 and Islamia Radoman, 1973 in terms of shell shape and protoconch surface. These differ from the present species in the either straight-sided ( Hauffenia , Islamia ; Arconada and Ramos 2006, Erőss and Petro 2008) or abapically (instead of adapically) sinuated peristome ( Horatia ; Szarowska 2006, Szarowska and Falniowski 2014). Shells of several species of Pontohoratia Vinarski, Palatov & Glöer, 2015 and Motsametia Vinarski, Palatov & Glöer, 2015 resemble Andrusovia species in terms of size and shape. They all differ in the more regularly shaped protoconchs, which show large nuclei and lack the massive growth constrictions.

Distribution.

Endemic to the Caspian Sea, reported from middle and south Caspian Sea at depths between 47 and 311 m ( Starobogatov 2000).

Figures

Figure 6. Hydrobiinae and Horatiinae. A, B, L Ecrobia cf. grimmi (Clessin in W. Dybowski, 1887), LV 201508 C, D E. cf. grimmi, RGM 1309845 E E. cf. grimmi, RGM 1309847 F, G Andrusovia brusinai Starobogatov, 2000, RGM 1309840 H, K, N A. brusinai, LV 201509 I, J, M A. brusinai, RGM 1309839.