Tonian Period

What happens during this time?

Geophysical

• The supercontinent Rodinia begins to break up

Biological

• Cyanobacteria present in the fossil record

  • Stromatolites begin to precipitously decline at about 1.0 Ga  (Bernard et al. 2013)

• Bitter Springs Formation (Australia) shows a diverse array of cells, called acritarchs

  • Acritarchs are small organic microfossils in marine sediments

  • Probably the remains of different organisms (early metazoans, ancestral fungi, and algae), some in their cyst stage

• Evidence of Green algae 

  • Filamentous algae fossils from this time show clean-cut circular holes in their cell walls, similar to the feeding damage by Vampyrella-like amoebae

  • Seaweed-like green alga, Proterocladus antiquus, from China found at roughly 1.0 Ga (Tang et al., 2020)

• Evidence of macroalgae from around 950 Ma from the Yukon of Canada (Phys.org; Maloney et al., 2021)

  • Multiple species of algae thrived together on the seafloor nestled between bacterial mounds in a shallow ocean

  • Researchers have identified a multicellular algae called Arctacellularia tetragonala that has chlorophyll derivatives (nickel-geoporphyrins), preserved in situ in the cells (Sforna et al., 2022)

• Evidence of fungi in the fossil record

  • Multicellular organic-walled microfossils with fungal affinities are found in the shale of the Grassy Bay Formation (Shaler Supergroup, Arctic Canada), approximately 1,010–890 million years ago (Loron et al., 2019)

  • Fossil filaments and mycelium-like structures with vestigial chitin, remnants of fungal networks, found in dolomitic shale from the Mbuji-Mayi Supergroup, Democratic Republic of Congo from 810 to 715 million year old (Bonneville et al., 2020)

    • Carbonaceous filaments of ~5 μm in width exhibit low-frequency septation (pseudosepta) and high-angle branching that can form dense interconnected mycelium-like structures

• Branching, tubular, meshlike structures found in Northwest Territories (Canada) might be evidence of horny sponges, and the oldest evidence of animals (Turner, 2021)

  • Although this is disputed as possible microbial or mineral traces