The emergence of the tropical rainforest biome in the Cretaceous

Modern tropical rainforests (TRFs) are one of the most ecologically important and species-rich biomes on the planet. However, the origin of modern TRFs is still debated, especially due to the incongruence between the fossil record and molecular data. Here, we test whether Campanian assemblages from northeastern Africa could represent fossil TRF vegetation. In so doing, we compare the investigated assemblages with other assemblages known to represent temperate forests, subtropical forests, and TRF in terms of leaf physiognomy, species richness, and taxonomic composition. We conclude based on fossil leaves that modern-looking TRFs already existed since 80 Ma during the Campanian in northeastern Africa in an area corresponding to 10 % of the modern Amazonian or 25 % of the Congolese TRF. The apparent conflict between the fossil record and phylogenetic evidence is due to the nearly complete absence of published tropical floras for the Cretaceous.