Eukaryotic organisms radiated in Proterozoic oceans with oxygenated surface waters, but, commonly, anoxia at depth. Exceptionally preserved fossils of red algae favor crown group emergence more than 1200 million years ago, but older (up to 1600-1800 million years) microfossils could record stem group eukaryotes. Major eukaryotic diversification ~800 million years ago is documented by the increa...

Abstract Here we present a detailed accounting of organic microfossils from late Ediacaran sediments Finland, the island Hailuoto (northwest Finnish coast), and Saarijärvi meteorite impact structure (~170 km northeast Hailuoto, mainland Finland). Fossils were recovered fine-grained thermally immature mudstones siltstones are preserved in exquisite detail. The majority forms sourced filamentous ...

On the basis of putative nuclei and endospores, Huldtgren et al. (Reports, 23 December 2011, p. 1696) propose that embryo-like Doushantuo microfossils are nonmetazoan holozoans akin to mesomycetozoeans. However, both size and preservation preclude interpretation of internal structures as nuclei. Moreover, the authors may have conflated two different populations; some specimens display a pseudop...