The Cenozoic Era
The Cenozoic Era 's place in the geologic time scale.
Modified from Kazlev 2002.
members of the family Equidae first appeared during the Cenozoic Era
(Prothero 1998). This was an era in which there was a great radiation
of mammals: the mass extinction at the Cretaceous-Tertiary boundary left
many niches open for the evolution new organisms (WGBH 2001). The Cenozoic
Era is the most modern geologic era: the beginning was marked by the
K-T extinction, and the era continues to the present. From the
earliest to the most recent, the Cenozoic Era is divided into the Tertiary
Period, which is subdivided into the Paleocene, Eocene, Oligocene, Miocene,
and Pliocene Epochs, and the Quaternary Period, which is subdivided into
the Pleistocene and Holocene Epochs (Kazlev 2002).