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.