Neogene herpetofauna, climate, and continental runoff of western Siberia
Final Report Abstract
During the final 18 month of the project ‘Neogene herpetofauna, climate, and continental runoff of Western Siberia’ we provide the herpetofaunal (42 localities) and precipitation data (13 localities). The successful collaboration with Dr. V. Zazhigin (Moscow) provided the most part of the material studied. To improve the faunal list we used also collections Dr. V. Chkhikvadze (Tbilisi) and Dr. M. Hodrova (Prague), as well as the available literature data after critically review. Taxonomic identification of the fossil material revealed over 50 salamander, frog, lizard, snake and turtle taxa from the Middle Miocene to Pleistocene. The late Middle Miocene localities have the most diverse faunas including all major groups of herpetofauna. Based on the faunistic analysis we suggest a Asiatic (Eastern Palaearctic) origin for Hynobiidae (asiatic samalanders), Proteidae (water dogs and olms), Bufotes viridis species group (green toads), brown frogs Rana arvalis. The main part of the herpetofaunal assemblage, including Palaeobatrachidae (extinct frog family), Pelobatidae (spadefoot toads), genera Chelotriton (crocodile salamanders), Bombina (i.e. Bombina (cf.) bombina; fire-bellied toads), Hyla (i.e. Hyla (cf.) savignyi; tree frogs), Pelophylax (green frogs), and Bufo bufo species group (european toads), has European (Weastern Palaearctic) affinities. The Western Siberian records of Mioproteus, Chelotriton, Bombina, Pelobatidae, Hyla, Bufo bufo and Rana arvalis represent the easternmost Eurasian records of those groups. The earliest Miocene dispersal of the green toad species group Bufotes viridis from Asia (? via Anatolia) into Europe can be documented. We suggest the same distribution pattern for brown frogs Rana too. We further summarize the available testudinoid fossil records from the Zaisan and Turgay Basins and Western Siberia. Analysing the testudinoids from the Zaisan Basin based on ecological adaptations (aquatic or terrestrial), we conclude that the climate changed from Early Miocene to Early Pliocene from humid to dry (presence or absence of the water reservoirs). So, the aquatic families dominated in the Early and Middle Miocene indicating mostly humid climate, whereas the presence of exclusively terrestrial forms – tortoises from the latest Middle Miocene to late Miocene indicates dry and open habitats in the Zaisan Basin. Nevertheless, based on these taxa the palaeoprecipitation values of their localities cannot be quantified. Only species-rich herpetofaunal assemblages enable these estimations. Describing the glass lizard (Anguinae) and snake faunas each, we suggest strong European influence in Western Siberian for these groups during Middle Miocene. Due to poor diversity of the herpetofaunal assemblage from the studied localities, we are able to estimate palaeoprecipitation values only for 13 fossil sites. According to our study, the precipitation development in Western Siberia shows high-amplitude changes during the studied interval contrary to previously known (palynologic) climate data. Aside from few localities, the humidity was significantly above the present-day values. Noticeably, for the time periods covered by data, the palaeoprecipition in Western Siberia shows the same temporal trends in comparison to (Central and Southwestern) European humidity developments. The decreasing tendency of the herpetofaunal diversity towards the end of the Neogene and Quaternary could be referred to the progressive global cooling and forced ice-sheet development in the Northern Hemisphere. Our available dataset is thus insufficient to be used to answer the second and third initial questions of the project. For our palaeoenvironmental analysis we include other fossil records of proxyorganisms (plants, birds, mammals) to round out the palaeoenvironmental picture for several fossil sites or Svitas. At two intervals during the Late Miocene (7.25 and 5.9 Ma) a significant extension of cool and arid environments can be shown by our humidity (MAP 160mm and 340mm, respectively) and temperature data (MAT <15˚C, CMT <8˚C), which corresponds well to available data for palynology, bird and mammal associations, indicating the spread of steppe environments up to latitude of 56°N. Further research will show, if these event are isochronous with the increase in eolian dust supply observed in the Atlantic and Pacific at the Tortonian-Messinian transition (7.3-7.2 Ma) and the onset of Messinian evaporites (5.96 Ma) in the Mediterranean area.
Publications
- 2012. Habitat tracking, range dynamics and palaeoclimatic significance of Eurasian giant salamanders (Cryptobranchidae) — indications for elevated Central Asian humidity during Cenozoic global warm periods. Palaeogeography, Palaeoclimatology, Palaeoecology 342-343: 64-72
Böhme, M., Vasilyan, D., Winklhofer, M.
(See online at https://doi.org/10.1016/j.palaeo.2012.04.032) - 2012. Mio-Pliocene herpetofauna of Western Siberia and its palaeoclimatic significance. RCMNS Interim Colloquium Paratethys-Mediterranean Interactions: Environmental Crises during the Neogene. 27-30 September 2012, Bucharest, Rumania. pp.117-118
Vasilyan, D., Böhme, M., Zazhigin, V., Winklhofer, M.
- 2012: Pronounced Peramorphosis in Lissamphibians—Aviturus exsecratus (Urodela, Cryptobranchidae) from the Paleocene–Eocene Thermal Maximum of Mongolia. - PLoS ONE 7(9): e40665
Vasilyan, D., Böhme, M.
(See online at https://doi.org/10.1371/journal.pone.0040665) - 2013. A new giant salamander (Urodela, Pancryptobrancha) from the Miocene of Eastern Europe (Grytsiv, Ukraine). Journal of Vertebrate Paleontology 33(2): 301-318
Vasilyan, D., Böhme, M., Chkhikvadze, V. M., Semenov, Y. A., Joyce W.G.
(See online at https://doi.org/10.1080/02724634.2013.722151)
