Abstract
The origin and development of Neotropical biomes are central to our understanding of extant ecosystems and our ability to predict their future. During the Cretaceous, biomass of tropical rainforests was mostly dominated by gymnosperms and ferns, forest structure was poorly stratified and the canopy was open and dominated by gymnosperms. Extant tropical rainforests first developed at the onset of the Cenozoic, as a result of the massive extinction of the Cretaceous – Paleocene boundary. Paleocene rainforests were multistratified, with an angiosperm–dominated canopy that had high photosynthetic potential. Tropical climate has followed global patterns ofwarmings and coolings during the last 60 Ma. Rainforest diversity has increased during the warmings while it has decreased during coolings. Several extant biomes, including páramos, cloud forest, savannas, and dry/xerophytic forest, have increase significantly during the late Neogene at the expense of the reduction of the rainforest. Timing and drivers of these changes are still unknown but seem to be related to the onset of our modern, cool–state climate since the onset of the Pleistocene, 2.6 Ma ago.