Cenozoic Era

Definition - What does Cenozoic Era mean?

The Cenozoic Era is an era related to mammals which was preceded by the Mesozoic era. It is the latest subdivision of the animal history; other two being Mesozoic and Paleozoic Eras. The Cenozoic era started when the Cretaceous Period ended and non-avian dinosaurs extinguished. It spans about 65 million years from the end of the Cretaceous Period. This era is also known as Age of Mammals because during this period many groups became extinct but mammals thrived and diversified.

Petropedia explains Cenozoic Era

The Cenozoic Era can be further subdivided into three periods:

Paleogene – This period ranges from 65 million to 55 million years ago from the extinction of dinosaurs.
Neogene – This period ranges from 23 million to 3 million years ago.
Quaternary – This period spans from 3 million years to present day.

Local or regional catastrophes extinguished all the mammals in the Cenozoic Era and buried them in the earth. With slow biological activities of micro-organisms on the buried corpses, these mammals were converted into various large or small oil and gas formations within the rocks.