Planorbis varians Fuchs, 1870

Neubauer, Thomas A., Harzhauser, Mathias, Georgopoulou, Elisavet, Mandic, Oleg & Kroh, Andreas, 2014, Replacement names and nomenclatural comments for problematic species-group names in Europe's Neogene freshwater Gastropoda, Zootaxa 3785 (3), pp. 453-468 : 464-465

Planorbis varians Fuchs, 1870 —how to recombine?

Planorbis varians Fuchs, 1870 in Fuchs 1870a: 356, pl. 14, figs 1–9.

Gyraulus (Gyraulus) varians (Fuchs) : Wenz 1923: 1622 (cum syn.).

Muellerpalia varians (Fuchs, 1870) ; Bandel 2010: 104 [not pl. 8, figs 90–94, = Muellerpalia bicincta (Fuchs, 1870) ]. Marinescugyra varians (Fuchs, 1870) ; Bandel 2010: 112, pl. 13, figs 153–158.

In his revision about the valvatiform gastropods of the Paratethys realm, Bandel (2010) introduced amongst others the genera Muellerpalia (Hydrobiidae) and Marinescugyra ( Planorbidae ), based on characteristic protoconch features. One of the discussed species is Planorbis varians Fuchs, 1870 from Rădmăneşti in Romania. On the grounds of different protoconch properties, Bandel assigned specimens, putatively belonging to the same species, to either Muellerpalia (p. 104) or Marinescugyra (p. 112). For the latter, it even constitutes the type species. Hence, Bandel used two different combinations based on the same original combination.

From a nomenclatural as well as a taxonomic view this is of course not tenable. It means that either the various specimens belong to two different species or the diagnostic features of the two genera are not meaningful. The associated problems were clear to the author as became evident from personal correspondence: Bandel (pers. comm.) stated the possibility that " Planorbis varians " is actually represented by two species, which would have to be assigned variably to Muellerpalia or Marinescugyra based on their protoconchs. Unfortunately, this discussion is wanting in the paper.

However, it turned out that the two combinations indeed refer to different species. The specimens illustrated by Bandel (2010) as " Marinescugyra varians " (pl. 13, figs 153–158) undoubtedly refer to the same species as described by Fuchs (1870a). They correspond in the two strong keels, the intermediate spiral lines, the slightly concave umbilical part, and the weakly stepped funnel-like apical part. In contrast, the individuals depicted as " Muellerpalia varians " ( Bandel 2010, pl. 8, figs 90–95) belong to a different species: they have both keels on the umbilical side, apparently lack additional spiral lines, have highly convex whorls, and more distinct growth lines. Direct comparison of the descriptions and illustrations of Fuchs (1870a, b) and Bandel (2010) suggest that Bandel confused several species. Firstly, " Muellerpalia varians " sensu Bandel rather corresponds to " Valvata bicincta Fuchs, 1870 " in Fuchs (1870b) [= Muellerpalia bicincta (Fuchs, 1870) ]. Secondly, specimens illustrated as " Muellerpalia bicincta " by Bandel rather resemble " Valvata carinata Fuchs, 1870 " in Fuchs (1870b) [= Muellerpalia carinata (Fuchs, 1870) ]. Conversely, Muellerpalia carinata (Fuchs, 1870) sensu Bandel, 2010 may represent Muellerpalia bicincta . The new combinations of both latter taxa with the new genus Muellerpalia still remain valid.

The presence of a second, fainter keel on the umbilical side in " Muellerpalia varians " sensu Bandel (2010) [= Muellerpalia bicincta (Fuchs, 1870) ], which is not discernible in the original material of Fuchs (1870a), is regarded as intraspecific variability herein, as all other features correspond quite well. Unfortunately, Bandel did not provide an illustration of the apical region, which would show a distinct keel if our determination as M. bicincta is correct. Nevertheless, the endpoint of keel-like structure is visible in the apertural view ( Bandel 2010, pl. 8, fig. 94). Even if it might turn out that this tentative placement is wrong, it still remains well separated from Marinescugyra varians .

In conclusion, the genus Marinescugyra, with Planorbis varians Fuchs, 1870 as type species, remains valid and the combination Marinescugyra varians (Fuchs, 1870) is the only accepted one. The combination Muellerpalia varians (Fuchs, 1870) is based on a misidentification of the species. We tentatively synonymize this record with Muellerpalia bicincta (Fuchs, 1870) .