Radiations and extinctions of plankton in the late Proterozoic and early Cambrian

Abstract

The intrinsic palaeobiological importance of planktonic algal microfossils of Proterozoic and early Cambrian age has been widely documented1–8. The evidence supporting the biostrati-graphical significance of planktonic microfossils in the correlation of Upper Proterozoic and Lower Cambrian sequences has also been assessed1,4–8. We contend here that both within-flora (α) and total (γ) taxonomic diversity trends for late Proterozoic planktonic microfossils indicate that a distinct radiation of presumed cyst-forming eukaryotic plankters occurred during late Riphean and early Vendian (used here in the sense introduced in refs 1, 8). Following this, a mid- to late Vendian extinction episode reduced observable plankton diversity by some 70%, extirpating most morphologically complex, pre-existing taxa. A second radiation restored high plankton diversity levels, but not until well into the early Cambrian.