ZOOGEOGRAPHY OF THE LATE OLIGOCENE BASINS OF WESTERN EURASIA BASED ONBIVALVE MOLLUSKS

The main difference between the distribution of Chattian and previous molluscan assembalges in Western Eurasia was the increase in the degre e of similarity of all the assemblages due to smooth climatic barriers and the extension of genera and species distribution areas. The north European and Mediterranean provinces continued to exist, but a wide t ransitional zone appeared between them. As earlier, the German and Eas t Paratethyan subprovinces may be distinguished.