1. PLEISTOCENE RODENTS FROM THE URALS AND WEST-SIBERIAN PLAIN: BIOCHRONOLOGICAL IMPLICATIONS ALEXANDER BORODIN presenter's e-mail: bor@ipae.uran.ru Institute of Plant and Animal Ecology RAS Ekaterinburg, Russia

2. The goal of our presentation is to give the biochronologic characteristic of rodents and especially arvicolids in Quaternary faunas of the Urals and West-Siberian Plain. Three points to be discussed: - Sequence of structural changes in molars - Molar size changes in some phyletic lineages - The changes in species composition of small mammal faunas The analyzed material includes the author’s collections and also some published data (Krukover 1992, Maleeva 1970, 1976, 1984, Maleeva & Stefanovski 1988, Smirnov 1994, 1996, Strukova 1999, 2002, Zazhigin 1980, Zudin et al. 1977, et al.)

3. Geographical location of the studied area

4. Geographical location of the sites of small mammal faunas in the Urals and West-Siberian Plain

9. Structural characteristics of rodents’ teeth

10. Stages of evolution in molars of West-Siberian arvicolid rodents

11. MQ zones of Quarternary in Western Europe, Urals and West-Siberian Plain

12. Size of vole teeth

13. Length of М/1 of recent M. (Stenocranius) gregalis from West-Siberian Plain

14. Length of М/1 of M. (Stenocranius) gregalis from the Neopleistocene and Holocene localities of the Trans-Urals

15. Length of М/1 of M. (Stenocranius) gregalis and L. lagurus from Neopleistocene and Holocene localities of the Trans-Urals Rs=0.973 P=0.0002

16. Paleoclimatic conditions in West-Siberian Plain (according to Arkhipov, 1994) and the position of studied faunas

17. Length of М/1 of M. (Stenocranius) gregalis and L. lagurus from Neopleistocene and Holocene localities of the Trans-Urals compared to the climatic changes

18. Species content

19. Landscape characteristic of Pleistocene faunas of West-Siberian Plain

20. Correlation of vole species ratio in local faunas of the Late Neopleistocene from Trans-Urals with the longitude and altitude of the site

21. Conclusions 1. The common patterns of arvicolid teeth evolution allow to reveal the reliable chronostratigraphic markers for the correlation of MQ zones of different regions within at least the central part and north of Eurasia. MQ subzones to a greater extent reflect the regional character of geological and biological events in Quaternary.

22. 2. The changes of teeth size could be considered as biochronological markers in only cases when they are not a direct result of the environmental influence. Teeth size of Neopleistocene M. gregalis and L. lagurus can not be adopted as biochronologic markers for the Urals and West-Siberian Plain because they were directly influenced by the climatic changes.

23. 3. The identification of the correct chronological stages of the changes in species content of small mammal faunas is only possible when we take into account the gradient of climatic conditions both in latitudinal, longitudinal and altitudinal directions.

24. Thank you for attention