Backdoor Formation, Collier Group, Bangemall Supergroup, Ectasian, Lower Ediacaran, Mesoproterzoic, Ashburton, Western Australia.

Li et al. 2023 in Communications Biology 6(1):399 noted that macrofossils with unambiguous biogenic origin and predating the billion-year-old multicellular fossils Bangiomorpha and Proterocladus (interpreted as crown-group eukaryotes) are rare. Horodyskia is found in successions dating from early Mesoproterozoic to terminal Ediacaran, but biogenecity had been uncertain. Li et al. (2023) reported carbonaceous compressions of Horodyskia from the Tonian (~950-720 Ma) of North China, the organic walls of which strongly support the biogenicity of Horodyskia. They reconstructed Horodyskia as a colonial organism composed of a chain of organic-walled vesicles thought to represent the multinucleated (coenocytic) cells of early eukaryotes. The study indicates that eukaryotes acquired macroscopic size through the combination of coenocytism and colonial multicellularity by at least ~1.48 Ga, and highlighted the exceptionally long range and morphological stasis of these Proterozoic macrofossils.