Paleocene

Pa le o cene |ˈpālēəˌsēn ˈpeɪliəˌsin | ▶adjective Geology of, relating to, or denoting the earliest epoch of the Tertiary period, between the Cretaceous period and the Eocene epoch. • (as noun the Paleocene ) the Paleocene epoch or the system of rocks deposited during it. The Paleocene epoch lasted from 65 million to 56.5 million years ago. It was a time of sudden diversification among the mammals, probably as a result of the mass extinctions (notably of the dinosaurs ) that occurred at the end of the Cretaceous period (see Cretaceous –Tertiary boundary ). ORIGIN late 19th cent.: from paleo- (relating to prehistoric times ) + Greek kainos ‘new. ’