We investigate the dynamics of ant biodiversity patterns and community structure from the Eocene until the present. Our goal is to empirically test hypotheses regarding the similarities in composition and structure of fossil and modern ant faunas to understand the historical processes influencing modern global biodiversity patterns.LocationGlobal.MethodsWe integrated two recently developed databases of the geographical distributions of fossil and modern ant genera and analysed the evolution of diversity and composition since the Eocene, c. 55 Ma. We assembled a third new database on community structure of ants, and used it to compare community structure of fossil assemblages with modern communities in different bioregions.ResultsThe analyses of generic composition and community structure were congruent, supporting a strong affinity between the Western Palaearctic ant fauna and modern Indomalayan and Australasian assemblages, and of a widespread Holarctic ant palaeofauna, and affinity between fossil Caribbean and modern Neotropical faunas. In addition, neither generic composition nor community structure of fossil assemblages showed evidence of taphonomic bias towards arboreal taxa.Main ConclusionsThe aggregated fossil record reveals the dynamic nature of macroecological patterns in ant biodiversity during the Cenozoic, with continental-scale generic extinctions common and important in shaping modern ant assemblages. Our results suggest major compositional changes for the Western Palaearctic bioregion and the Caribbean bioregions. The ant palaeofauna of the Western Palaearctic bioregion was then very similar in composition and structure to the one observed now in the Indomalayan bioregion, supporting the notion that modern-day ‘tropical’ biomes were historically much more widespread, while temperate biotas are more recently evolved. Our results underscore the importance of a palaeogeographical perspective in understanding modern-day macroecological patterns.