. Asiatic herpetological research. Reptiles -- Asia Periodicals; Amphibians -- Asia Periodicals. FIG. 15. The shield-headed vipers from the Caucasus, a. Vipera kaznakowi, b. V. dinniki, c. V. ursini renardi, d. V. dinniki (Lagodekhi, Georgia. ZIN 8389). phylogenetically close species and felt that montane populations of the vipers played a big role in the formation and isolation of the forms. In his opinion, when it became cold they were forced out of the mountains onto the plains by glaciers. When the climate became warm again, they retreated into the mountains. In the mountains it was easy t
. Asiatic herpetological research. Reptiles -- Asia Periodicals; Amphibians -- Asia Periodicals. FIG. 15. The shield-headed vipers from the Caucasus, a. Vipera kaznakowi, b. V. dinniki, c. V. ursini renardi, d. V. dinniki (Lagodekhi, Georgia. ZIN 8389). phylogenetically close species and felt that montane populations of the vipers played a big role in the formation and isolation of the forms. In his opinion, when it became cold they were forced out of the mountains onto the plains by glaciers. When the climate became warm again, they retreated into the mountains. In the mountains it was easy to choose temperature and humidity optima, whereas on the plains this was not possible. Kramer felt that in some places on the plains where refugia might be present, the climate remained more or less stable. For the vipers in the V. ursini complex, Kramer suggests first separation in the Miocene and Pliocene and later independent development of the eastern and western forms. The complex formation of the climate and relief in the Caucasus coincides with regular regressions and transgressions of the sea. Breaks in links between the faunas of the Caucasus and the European platform, the Balkans and Turkey stipulate emergence and isolation of original viper forms, beginning with the Miocene and Pliocene. At this time the formation of the Caucasus as a montane country occurred (Bogachev 1938). Schwarz (1936) suggests that the viper fauna of the Mediterranean islands are Miocene relicts. Present ranges of shield-headed vipers in. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Asiatic Herpetological Research Society; Chung-kuo liang chi pa hsing tung wu hs©eh hui. Berkeley, Calif. : Asiatic Herpetological Research Society : Chinese Society for the Study of Amphibians and Reptiles
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