The simple species diversity (both recorded and cumulative) of deep sea Ostracoda throughout the Cainozoic of the Southwest Pacific is shown to fluctuate considerably as does the level of originations and extinctions of species. The former exceed the latter throughout the Palaeocene and Eocene thus allowing diversity to build up to its acme in the middle Eocene where, in NP Zone 16 extinctions exceed originations for the first time. These events, the subsequent late Eocene/early Oligocene diversity crash followed by a recovery into the late Oligocene, and the diversity and evolutionary high low points of the Neogene and Quaternary, are discussed with reference to contemporary oceanic events and compared to circumstances in other oceans.