The previous eras
(Paleozoic and Mesozoic) are divided in a simple way because the
information that is had of them is smaller, in comparison with the one
that is had about the Cenozoic era. The Cenozoic Era has
more recent fossil records, well preserved, the rocks are younger and it
is easier to divide into short and very defined periods of time, unlike
the previous eras, where there are many gaps in the history of the
earth to define it . That great
information and greater precision, is the reason for a different
classification, and the names given to the periods, within the Cenozoic
era.
