Hi PrimateDave, hope all is well.
Sorry it took me this long but this is your answer:
The Cenozoic, is the most recent of the three classic geological eras and covers the period from 65.5 million years ago to the present.
The Cenozoic is the age of new life. During the Cenozoic, mammals diverged from a few small, simple, generalized forms into a diverse collection of terrestrial, marine, and flying animals. The Cenozoic is just as much the age of savannas, or the age of co-dependent flowering plants and insects. Birds also evolved substantially in the Cenozoic.
Take Care,
Ismael