133845.pdf

CENOZOIC BIODIVERSITY 159

Fig. 3. Disruption of a circum-equatorial seaway by Cenozoic plate tectonic movements. Late Cretaceous (75
Ma BP): equatorial circulation dominated by a strong westerly flowing current system; no major biotic
differentiation. Late Eocene (40 Ma BP): partial initiation of a circum-Antarctic current and some
intensification of Pacific and Atlantic oceanic gyres. Middle Miocene (15 Ma BP): closure of Tethys in the
Mediterranean region, closure of the Indonesian seaway, and earliest beginnings of the uplift of the Central
American Isthmus. Circum-Antarctic current fully formed and Pacific and Atlantic oceanic gyres intensified.
This was the time of initiation of the IWP and ACEP high-diversity foci. Arrows indicate principal current
directions. Redrawn and simplified from Veron (1995, figs 28-30).