In the early Cenozoic era, after the dinosaurs became extinct, the number and diversity of mammals exploded. In just 10 million years -- a brief flash of time by geologic standards -- about 130 ...

3 min read At the dawn of the Paleogene—the beginning of the Cenozoic era—dinosaurs ... Rodent-size (and perhaps larger) mammals emerged, suddenly free to fill the void.

After the dinosaurs died out, mammals evolved into many different shapes and sizes as they filled the empty spaces left by the dinosaurs during the Cenozoic era. This period is also called the ...