Article: Microbiotas of the late Precambrian Ryssö Formation, Nordaustlandet, Svalbard

Silicified carbonates of the uppermost Riphean (800-700 Ma) Rysso Formation, Nordaustlandet, Svalbard, contain abundant, well-preserved microfossils that represent several palaeoenvironmental settings, life habits, and trophic modes. The fossils fall into three distinct assemblages. A stromatolitic microflorule preserved in flat cryptalgal laminated cherts includes seven taxa: three mat building cyanobacteria, two mat-dwelling or probable mat-dwelling blue-greens, one allochthonous element, and one rare species of indeterminate ecological role. An open coastal planktonic assemblage contains fourteen distinguishable taxa, including many acritarch species that have commonly been found in Upper Riphean shales and siltstones. The third assemblage is dominated by organically preserved skeletons and siliceous casts of vase-shaped heterotrophic protists. Collectively, these assemblages provide an unusually broad picture of microbial life in the Late Proterozoic Era. The Rysso Formation contains twenty-one taxa, of which one, Scissilisphaera regularis gen. et sp. nov., is formally described as new.