Hans Gadow, The Cambridge natural history, Vol… (1909)
“ The Urodela thus lend no support to the usual division of the Periarctic into a Palaearctic and a Nearctic sub-region. Nor is it possible to divide the Palaearctic into a Eurasian and a Mediterranean province. We have in this case to distinguish between an American, an Asiatic, and a European fauna. The Asiatic or Eastern Palaearctic sub-region assumes the central position, at least from a merely geographical point of view. It would be unjustifiable to assume a spreading from this centre into Europe, and, on the other hand, into America. ”
