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Abstract
A new fossil species of the pond snails (family Lymnaeidae Rafinesque, 1815), Lymnaea bogatschevi sp. n., from the Neogene (Khersonian–Maeotian transition) of southern Russia is described. It is characterised by a peculiar structure of the shell suture not found elsewhere in the family Lymnaeidae (both in living and extinct taxa). The suture of L. bogatschevi sp. n. may be described as a narrow groove that penetrates deep into the shell matter. This feature is developed both in protoconch and teleoconch whorls and is presented in several 100s of specimens that precludes its origin as an individual abnormality. There are no environmental factors known to induce such groove-like sutures in aquatic pulmonates indicating a genetic basis for this structure in L. bogatschevi. Also, we report a single shell with the similar channelled suture from a sample of Lymnaea megarensis (Gaudry in Fischer, 1867) from the Pliocene of Greece. It seems, in this species the groove-like suture was represented as a rare individual aberration, and later this trait disappeared completely from the lymnaeid morphological repertoir. Possible phylogenetic relationships between L. bogatschevi and the recent L. (Kazakhlymnaea) taurica (Clessin, 1880) are suggested and briefly discussed.
Acknowledgments
The authors thank museum curators helped us during work with collections: Ted von Proschwitz (NMG), Pavel V. Kiyashko and Lidiya L. Yarokhnovich (ZIN), Anita Eschner and Thomas A. Neubauer (NHMW). Thomas is also acknowledged for making photos of two shells of L. megarensis under our request and critically reading the initial version of the text. We thank Vitaly V. Anistratenko (Institue of Zoology, National Academy of Sciences of Ukraine, Kiev) and Alexei S. Tesakov (GIN) who made useful comments upon the manuscript.