The two warmest time periods on Earth in the past 140 million years drove both mass extinctions and explosions in plant diversity, according to researchers in Australia and Austria who say this could explain how flowering plants became dominant among land plants. The study, published in Nature Plants, examined fossilized pollen and spores to show that the mid-Cretaceous and early Cenozoic periods of extreme global warmth were central to plant evolution. This applies not only to flowering plants, but also to the other main land plant groups.