Early-middle Ediacaran organic-walled microfossils from the Doushantuo Formation studied in several sections in the Yangtze Gorges area, South China, show ornamented cyst-like vesicles of very high diversity. These microfossils are diagenetically permineralized and observed in petrographic thin-sections of chert nodules. Exquisitely preserved specimens belonging to seven species of Appendisphaera, Mengeosphaera, Tanarium, Urasphaera and Tianzhushania contain either single or multiple spheroidal internal bodies inside the vesicles. These structures indicate reproductive stages, endocyst and dividing cells, respectively, and are preserved at early to late ontogenetic stages in the same taxa. This new evidence supports the algal affiliations for the studied taxa and refutes previous suggestions of Tianzhushania being animal embryo or holozoan. The first record of a late developmental stage of a completely preserved specimen of T. spinosa observed in thin-section demonstrates the interior of vesicles with clusters of identical cells but without any cavity that is diagnostic for recognizing algal cysts vs animal diapause cysts. Various lines of evidence to infer biological affinities of these microfossils – morphology, reproductive characters, spatial arrangement of cells, and biochemical properties of the vesicle wall – are collectively characteristic of algal clades. Recognizing the biological affinities of these microfossils is key to understanding whether animals capable of producing such morphologically complex diapause cysts had an early Ediacaran fossil record (633–610 Ma), or the microfossils were non-animal holozoans or algae as argued herein for Tianzhushania spinosa and other studied microfossils.

Detrital zircon U–Pb ages from samples of the Neoproterozoic Visingsö Group, Sweden, yield a maximum depositional age of ≤ 886±9 Ma (2σ). A minimum depositional age is established biochronologically using organic-walled and vase-shaped microfossils present in the upper formation of the Visingsö Group; the upper formation correlates with the Kwagunt Formation of the 780–740 Ma Chuar Group in Arizona, USA, and the lower Mount Harper Group, Yukon, Canada, that is older than 740 Ma. Mineralized scale microfossils of the type recorded from the upper Fifteenmile Group, Yukon, Canada, where they occur in a narrow stratigraphic range and are younger than 788 Ma, are recognized for the first time outside Laurentia. The mineralized scale microfossils in the upper formation of the Visingsö Group seem to have a wider stratigraphic range, and are older than c. 740 Ma. The inferred age range of mineralized scale microfossils is 788–740 Ma. This time interval coincides with the vase-shaped microfossil range because both microfossil groups co-occur. The combined isotopic and biochronologic ages constrain the Visingsö Group to between ≤ 886 and 740 Ma, thus Tonian in age. This is the first robust age determination for the Visingsö Group, which preserves a rich microfossil assemblage of worldwide distribution. The organic and mineralized microorganisms preserved in the Visingsö Group and coeval successions elsewhere document global evolutionary events of auto- and heterotrophic protist radiations that are crucial to the reconstruction of eukaryotic phylogeny based on the fossil record and are useful for the Neoproterozoic chronostratigraphic subdivision.