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Proterozic and Early Cambrain Proteins: Evidence for Accelerating Evolutionary Tempo
Andrew H. Knoll
Proceedings of the National Academy of Sciences of the United States of America
Vol. 91, No. 15 (Jul. 19, 1994), pp. 6743-6750
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/2365159
Page Count: 8
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In rocks of late Paleoproterozoic and Mesoproterozoic age (ca. 1700-1000 million years ago), probable eukaryotic microfossils are widespread and well preserved, but assemblage and global diversities are low and turnover is slow. Near the Mesoproterozoic-Neoproterozoic boundary (1000 million years ago), red, green, and chromophytic algae diversified; molecular phylogenies suggest that this was part of a broader radiation of "higher" eukaryotic phyla. Observed diversity levels for protistan microfossils increased significantly at this time, as did turnover rates. Coincident with the Cambrian radiation of marine invertebrates, protistan microfossils again doubled in diversity and rates of turnover increased by an order of magnitude. Evidently, the Cambrian diversification of animals strongly influenced evolutionary rates within clades already present in marine communities, implying an important role for ecology in fueling a Cambrian explosion that extends across kingdoms.
Proceedings of the National Academy of Sciences of the United States of America © 1994 National Academy of Sciences