lectmay4

Macroevolution

The Cenozoic has been called the Age
of Mammals, probably because the name was given by mammals. It might have been called the Age of Insects, or the Age of Birds. If we want to ,get out of that emphasis on land organisms (after all, there is more ocean than land), we could call it the Age of Teleost Fish (modern fish), all of which groups showed major increases in number of species. If we want to pay attention to the organisms that form the base of the food chain on land, we could call it as well the Age of Angiosperms. In the beginning of the Cenozoic the overall global diversity was relatively low, because of the mass extinction at the end of the Cretaceous. Particularly the niche for 'large animals on land' was empty after the demise of the dinosaurs. Into this open niche birds and mammals diversified rapidly.