The Cretaceous Terrestrial Revolution (abbreviated KTR), also known as the Angiosperm Terrestrial Revolution (ATR) by authors who consider it to have lasted into the Paleogene, describes the intense floral diversification of flowering plants (angiosperms) and the coevolution of pollinating insects (especially anthophilans and lepidopterans), as well as the subsequent faunal radiation of various frugivorous, nectarivorous and insectivorous terrestrial animals then at the lower food web levels such as mammals, avialans (early birds and close relatives), squamate reptiles (lizards and snakes), lissamphibians (especially frogs) and web-spinning spiders, during the Cretaceous period.
After the K-Pg extinction event devastated the Mesozoic terrestrial ecosystems and wiped out nearly all animals weighing more than 25 kg (55 lb), the survivors among these smaller animals that thrived during the KTR recovered first to reoccupy the ecological niches vacated by the extinction of non-avian dinosaurs and pterosaurs, and therefore became the dominant clades of the Cenozoic terrestrial faunas. Flowering plants also quickly became the mainstream florae during the Cenozoic, replacing the previously more prevalent gymnosperms and ferns.
