Some Precambrian trace fossils have been presented as evidence for the early origin of bilaterians; the recent finding that large amoeboid protists leave macroscopic traces at the bottom of the deep ocean questions the metazoan nature of early trace fossils, stressing the importance of single-cell organisms in Precambrian biota.

The fossil record of fungi and lichens is scarce. Here we report the discovery of lichen-like fossils, involving filamentous hyphae closely associated with coccoidal cyanobacteria or algae, preserved in marine phosphorite of the Doushantuo Formation (between 551 and 635 million years old) at Weng'an, South China. These fossils indicate that fungi developed symbiotic partnerships with photoautot...

How to tell time: • Relative Time: putting events in time order. • Law of Superposition • Correlation of rock layers using fossils. William Smith " There is a wonderful order and regularity with which nature has disposed of fossils and assigned to each its peculiar stratum. " How to tell time: • Absolute Time: Determining age in years.