Recognizing and interpreting the fossils of early eukaryotes.

Using molecular sequence data, biologists can generate hypotheses of protistan phylogeny and divergence times. Fossils, however, provide our only direct constraints on the timing and environmental context of early eukaryotic diversification. For this reason, recognition of eukaryotic fossils in Proterozoic rocks is key to the integration of geological and comparative biological perspectives on protistan evolution. Microfossils preserved in shales of the ca. 1500 Ma Roper Group, northern Australia, display characters that ally them to the Eucarya, but, at present, attribution to any particular protistan clade is uncertain. Continuing research on wall ultrastructure and microchemistry promises new insights into the nature and systematic relationships of early eukaryotic fossils.