Mammals are undoubtedly the best fossils that can be used to establish the continental biochronology of Cenozoic times as well as the biotratigraphy of the lithologic units which yield the faunas. Different zonations in different areas are demonstrated, with emphasis on the Neogene. The main arguments used consist of evolutionary changes (successive evolutionary stages within an anagenetic lineage) or of events (first and last occurrence of taxa). Biochronology gives relative data; if we wish to have numerical data, we must correlate these results with radiometric data, marine biostratigraphic units or geomagnetic polarity time scale. Several palaeontologically restricted calibrations have been recently proposed. These methods are recent ones; they have been developed with the increasing availability of computers and followed by improvement in morphometrics. Immigrations first examined as a biochronological tool, are analysed within their palaeobiogeographical context. Routes and times of dispersal events are briefly evoked and these dispersal events are tentatively correlated with global events (eustasy, climatic changes, tectonic phases).

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