Volume 22

Results of ecological and zoogeographical study of the Middle Sarmatian gastropod molluscs of the Eastern Paratethys are presented. A comprehensive list of species and taxonomical remarks on some groups is provided. Some autecological characters of gastropods as well as the ratio of life forms with different diets are analyzed. The geographical areas of high abundance and maximal diversity of gastropods in the Eastern Paratethys correspond to the limits of bryozoan bioherms distribution; the latter are considered here as a chain of islands. Bryozoans served as edificatory factor for the Bessarabian Basin reef community in which gastropods played the leading role. The faunal characteristic is provided for the Sarmatian Bioherm Zoogeographical Province previously proposed by the authors. Malacofauna of the province is characterized by a high degree of endemism – around 55% of species and about 30% of genera are endemic. The distinctiveness of this zoogeographical unit started to form around end of the Early-Sarmatian time, it was most pronounced during the Middle Sarmatian (Bessarabian), and fauna became extinct during the freshening of the Sarmatian Basin during Late Sarmatian time. Taxonomic composition of gastropod fauna of different regions of the Middle Sarmatian (Bessarabian) Basin shows that Galician Gulf (West Ukraine and Moldavia) is the principal centre of diversity and origin of mollusks within the Eastern Paratethys and, perhaps, in the whole Sarmatian basin. This was caused by the fact of existence of bioherms at the Badenian and Early-Sarmatian time. A latitude gradient registered in the molluscs diversity – impoverishing from west to east connected with an asynchrony (retardation) of the bioherms formation in other regions i.e. Enikale Strait (Kerch and Taman peninsulas), Stavropol Strait (Central Ciscaucasus) and Mangyshlak Archipelago (northern part of Mangyshlak peninsula). The term ephemerous faunas is suggested for the Sarmatian and others shortly-lived endemic faunas of the Paratethys.

The shells of Oxychilus koutaisanus mingrelicus unknown earlier for Ukraine were discovered among the materials collected on the territory of the Donetsk Region in 1990-th. The unpdated information about the distribution on the territory of Ukraine of another Caucasian species, Stenomphalia ravergiensis , is provided. The presence of these species in the south-east of Ukraine can be result of the anthropochory.

The structure of reproductive tract of 15 species and subspecies (forms) of European (mainly Alpine) and South African Orculidae has been studied. For 12 of them the spermatophores were discovered and described or the characters undoubtedly indicating presence of spermatophore have been found (inner structure of the epiphallus). The presence of spermatophores as such is established for 5 species. Hypotheses about the possible historical relationships among subfamilies and genera of Orculidae and among species in the genus Orcula are presented.

The present-day data on geographical distribution and variability of three recent species of Aenigmomphiscola Kruglov et Starobogatov, 1981 (Lymnaeidae) are reviewed. More specific information concerning type series of two Aenigmomphiscola species is obtained. It is revealed that the species Ae. uvalievae and Ae. kazakhstanica cannot be distinguished in syntopy by their conchological traits, and, possible, these are conspecific. Judging from reliable records, the range of the genus Aenigmomphiscola covers a part of the East-European (Russian) plain, Southern Urals, the southern part of Western Siberia (including Altay), and Central Kazakhstan. Perhaps, representatives of the genus will be found in the future in another parts of Siberia and adjacent territories.