Summary Biogeography is the study of the distribution patterns of organisms. The biogeographical patterns associated with the radiation of individual clad during the Early Palaeozoic reflect a complex combination of plate distribution, tectonic activity, sedimentary environment, sea-level rise and climatic gradient. Geographical distributions of terrestrial or aquatic taxa that are broken up by oceans can be explained by either oceanic dispersal or vicariance in the form of fragmentation of a previously contiguous landmass. The present mammals evolution and distribution patterns are largely...