An introduction to Cenozoic (65 million years) This era is the last division of three main periods of animals'history. The other two eras are Paleozoic and Mesozoic. Cenozoic took about 65 million years. It commenced from late Cretaceous to non-avian dinosaurs' extinction up to now. This era is also called as Mammals Age because in comparison to other ages, mammals' population is a lot in Cenozoic. This name for Cenozoic is not very suitable due to the following reasons; -First, the history of mammals commences much earlier than this era. -Second, although this era has had a lot of mammals and it can be called mammals era, but flowering plants, insects and teleost fish (fish having completely bony vertebrate column and thin and smooth scales) eras are also suitable. Cenozoic is divided to two parts; Tertiary and Quaternary. Tertiary is longer than Cenozoic (from 65 till 8.1 million years ago). Quaternary takes 8.1 million years. Tertiary divides to two parts, Paleogene and Neogene. Divisions of Cenozoic The front table indicates these divisions This era has been divided to two parts; Paleogene and Neogene This era is in continuation of Mesozoic.