Select all of the answers that apply. why do some people argue that the cenozoic era should not be called the "age of mammals"? there are no mammals present during this era. flowering plants are just as common during this era. insects are equally as abundant during this era. birds are just as widespread as mammals during this era.

Birds are just as widespread as mammals during this era.

In Cenozoic era birds of Eocene epoch were the giant birds. These giant birds  were the members of family Diatrymidae, which were six feet tall. These birds were widespread in the early Cenozoic era, after the extinction of dinosaurs and before large land mammals evolved. Therefore, the Cenozoic era should be known as "Age of birds".