Abstract
Snake diversity of the Aralo-Caspian basin includes 61 species in 8 families, being composed of local faunas of the Northern Caspian Depression, the Greater Caucasus and Ciscaucasia, the Lesser Caucasus and Transcaucasia, the Alborz and Turkmeno-Khorasan mountains, the Aralo-Caspian Isthmus, the deserts and mountains of Middle Asia and the plains of the Aral Sea region. Regions with the richest snake diversity are Alborz, Turkmeno-Khorasanian Mountains and Transcaucasia. The snake fauna is composed of 25 biogeographic groups; all diversity of the distribution patterns is described by 10 main chorotype groups and 36 basic chorotypes. The most common element is Mediterranean (12 species), as well as Armeno-Iranian (7 species). Delta-diversity grows in the latitudinal direction, from the plains of the Aral Sea region and the North Caspian Lowland to the mountain systems of the Iranian Plateau. The level of species endemism is 25%. Six of the fourteen endemics live in the Alborz Mountains.