Pli·o·cene 
(plīə-sēn′)
(plīə-sēn′)adj.
Of, relating to, or being the epoch of geologic time from 5.3 to 2.6 million years ago, the most recent epoch of the Tertiary Period. It is characterized by the appearance of distinctly modern animals and by the expansion of grasslands. See Table at geologic time.
n.
The Pliocene Epoch.
[Greek pleiōn, more; see pelə-1 in the Appendix of Indo-European roots + -CENE.]