Models of historical biogeography and continental biochronology

One of the most important contributions of Nieves Lopez Martinez in Palaeobiogeography is the study of the ‘centre of origin of species’ concept and the proposal of the ‘Asymmetric Time Model’ as an alternative to the ‘Symmetric Time Model’, a key concept in dispersalist Historical Biogeography. As a consequence of these ideas, she discussed the methodology to establish biostratigraphic scales, pointing out that the higher number of ‘First Appearance Datum’ (FADs) over that of ‘Last Appearance Datum’ (LADs) in the fossil record supports the Asymmetrical Time Model. In this study we analyse the middle Miocene micromammal appearance and extinction events (FADs and LADs) based on well-calibrated local biostratigraphic scales from different European basins, in order to determine which of the proposed biogeographical models better fi ts the Miocene European micromammal record. The results support that the Asymmetric Time Model of palaeobiogeography is only applicable in rare cases. The analysed fossil record only shows one event of occurrence and one of extinction that can be considered synchronous at continental level. Finally, the implications of the biogeographic models in the proposition of biochronologic continental scales are also discussed, pointing out that palaeobiogeographic frameworks need robust biochronologies based on extensive local biostratigraphic data with independent temporal correlation.