An eukaryote-bearing microbiota from the early mesoproterozoic Gaoyuzhuang Formation, Tianjin, China and its significance

On the basis of expanded documentation of complex fossils, early Mesoproterozoic has already been proven as an important Era for eukaryotic evolution. In order to portray the biological community of this critical era, we studied a new silicified microbiota from the ∼1560 Ma Gaoyuzhuang Formation in the classic Jixian section, Tianjin, China. In total, eighteen species have been recognized, four species have been identified informally and five species have been identified in open nomenclature. Similar to other Proterozoic microbial mat biota, the new microbiota is dominated by cyanobacteria filaments and coccoids as well. Potential eukaryotic microfossils, such as ornamented coccoids, filaments with flanges and terminal cell, were firstly recovered. Amongst them, filaments with flanges and conidia-like terminal cell probably were the earliest unidirectional growing multi-cellular organisms as well as the earliest phylogeny-resolved multicellular eukaryotes. Combined with increasing records of Proterozoic eukaryotes, these microfossils indicated that eukaryotes have evolved into a new level in Early Mesoproterozoic.