The emergence of the tropical rainforest biome in the Cretaceous

Abstract. Modern tropical rain forests (TRF) are one of the most ecologically important and species-rich biomes on the planet. However, the origin of modern TRF is still debated, especially due to the incongruence between the fossil record and molecular data. Here, we are testing whether Campanian assemblages from north-eastern 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 assume that modern-looking TRF already existed about 80 Ma ago during the Campanian in north-eastern Africa based on fossil leaves 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 more or less absence of published tropical floras for the Cretaceous.