New record of the green algal fossil Proterocladus and coexisting microfossils from the Meso-Neoproterozoic Diaoyutai Formation in southern Liaoning, North China

•Well-preserved organic-walled microfossils are reported from the Meso-Neoproterozoic Diaoyutai Formation in North China.•The Diaoyutai microfossils experienced low-grade metamorphism with apparent peak metamorphic temperatures of ∼ 215 °C.•Green algal fossil Proterocladus antiquus in the Diaoyutai assemblage might be earlier than the previously reported occurrence in the Nanfen Formation.•Relatively high abundance of eukaryotes is observed in the Diaoyutai assemblage.•Microbial ecosystem structure in the shallow marine environment is reconstructed.