Theodoxus pallasi

Wesselingh, Frank, Poorten, Jan Johan ter, Kijashko, Pavel, Albrecht, Christian, Anistratenko, Olga Yu, Frolov, Pavel, Gándara, Alberto Martinez, Gittenberger, Arjan, Gogaladze, Aleksandre, Mikhail Karpinsky, Popa, Luis, Sands, Arthur F, Vandendorpe, Justine & Wilke, Thomas, 2019, Mollusc species from the Pontocaspian region - an expert opinion list, ZooKeys 827, pp. 31-124 : 61-62

Theodoxus pallasi Lindholm, 1924

°1838 Neritina liturata Eichwald: 156-157 [non Neritina liturata Schultze, 1826].

*1924 Theodoxus pallasi Lindholm: 33, 34 [nom. nov. pro Neritina liturata Eichwald, 1838, non Schultze, 1826].

1947 Theodoxus (Theodoxus) pallasi var. nalivkini Kolesnikov: 106, 110.

1976 Theodoxus pallasi Lindholm, 1924. - Akramovskiy: 88, text fig. 23, pl. 1, figs 1, 2.

1994 Theodoxus astrachanicus Starobogatov in Starobogatov, Filchakov, Antonova and Pirogov: 8-9, fig. 1(1, 2).

1994 Theodoxus astrachanicus Starobogatov et al.: 8-9, fig. 1(1, 2).

2009 Theodoxus pallasi Lindholm, 1924. - Filippov and Riedel: 70, 72, 74, 76, fig. 4 g–i.

2011 Theodoxus astrachanicus Starobogatov in Starobogatov, Filchakov, Antonova & Pirogov, 1994. - Anistratenko et al.: 54-55, fig. 1(6).

2012 Theodoxus pallasi Lindholm, 1924. - Welter-Schultes: 29, unnumbered text figures.

2016 Theodoxus (Theodoxus) astrachanicus Starobogatov in Starobogatov, Filchakov, Antonova & Pirogov, 1994. - Vinarski and Kantor: 155-156.

2016 Theodoxus (Theodoxus) pallasi (Lindholm, 1924). - Vinarski and Kantor: 156-157 [and synonyms therein].

2017 Theodoxus pallasi Lindholm, 1924. - Anistratenko et al.: 221, figs 4, 7, 10, 11.

2018 Theodoxus pallasi Lindholm, 1924. - Neubauer et al.: 48-51, fig. 4 A–F.

Status. Accepted Pontocaspian species, name uncertain.

Type locality. "Inter Fucos littoris Derbendensis viva" (living among algae on the shores of Derbent), Dagestan, Russia.

Distribution. Present along the Caspian Sea shores, in the Volga River, and the Sea of Azov. Lived until the late 1980s in the Aral Sea but is possibly extinct there now ( Andreev et al. 1992, Aladin et al. 1998, Micklin et al. 2014).

Taxonomic notes. Eichwald (1838) introduced the species Neritina liturata based on material from the shores of Derbent (Dagestan, Russia, northwestern Caspian Sea). That name is invalid as it is a junior primary homonym of N. liturata Schultze, 1826; it was replaced by Lindholm (1924) with Theodoxus pallasi (see also Anistratenko et al. 2017). Theodoxus pallasi is a widely used name, but a major nomenclatural change might be due. Unpublished molecular data suggest that all Theodoxus from the Caspian Sea, Azov Sea, and Armenian lakes Sevan and Yerevan, as well as several mineral springs and streams in the Khorasan provinces of Iran, belong to a single species (AFS, unpublished results). The oldest name available for that group is Theodoxus major Issel, 1865, described from Lake Sevan in Armenia (originally as variety of the unavailable name T. schirazensis ). Akramovskiy (1976) noted the similarity of T. pallasi and T. major and considered the latter as a morphotype of the former. Although he did not explicitly state it, he thereby suggested the two taxa to be synonymous. This view was adopted by Vinarski and Kantor (2016), who listed major in synonymy of pallasi , although Issel’s (1865) name has priority. The potential synonymy also involves T. schultzii . Despite the characteristic appearance of the syntypes, the presence of intermediate morphologies in samples taken on shores of Azerbaijan and Kazakhstan in 2016 and 2017 (pers. obs. OA, VA, FW) indicates a close relationship with T. pallasi. The radulae of these two species differ in the relative width of the central and marginal teeth (see Zettler 2007 and compare Anistratenko et al. 2017).

Unfortunately, the types of T. major , supposed to be in the Museo Regionale di Scienze Naturali, Torino, are inaccessible at the moment due to museum renovation (E Gavetti, pers. comm., Oct 2018). We refrain from a final conclusion on the synonymy of the species involved until information on the types of all taxa as well as published molecular data are available. For details on the taxonomic relationship between T. pallasi and T. astrachanicus , see discussion in Anistratenko et al. (2017).

Conservation status. Data Deficient ( Van Damme and Kebapçı 2014).