Beginning of Paleocene

By the beginning of the Paleocene, not only had the K-T boundry just passed, but also most of New Zealand's land was eroded causing the sea to encroach in the lowlands and huge swamps to form. It is around this time that New Zealand's short tailed bat arrived. The bat is New Zealand's only native mammal.

Some time in the Paleocene, three families of birds arrived: New Zealand wrens, native thrushes, and wattlebirds. Because New Zealand was isolated, only creatures who could fly where able to migrate.