Carbonaceous macrofossils from the early Mesoproterozoic Gaoyuzhuang Formation in the Yanshan Range, North China

The emergence of multicellular organisms is a critical milestone in the evolution of life on Earth. Fossils characterized by multicellular organization are known to occur in the pre-Ediacaran sediments, which provides unique insights into the evolution of multicellularity and eukaryotic ecosystems. The current oldest unambiguous evidence for macroscopic multicellular eukaryotes comes from the decimeter-sized carbonaceous macrofossils reported from the ∼1560-million-year-old Gaoyuzhuang Formation in the Yanshan Range, North China. These blade-like fossils displayed regular elongated morphologies and large dimensions up to several centi- to deci-meters, and were inferred to be multicellular eukaryotes with a regular developmental program but of unknown phylogenetic affinity. With numerous new specimens collected, we formally described these macrofossils here and identified 5 form taxa, including one new genus and three new species, namely, Grandilingulata qianxiensis gen. et sp. nov. (tongue-shaped), Tuanshanzia linearis sp. nov. (cuneate to linear), Tuanshanzia parva sp. nov. (small, linear), Tuanshanzia fasciaria (oblanceolate) and filamentous Proterotainia sp. Our current collection reveals similar fossil content to those previously reported, confirming their morphological consistency. The Gaoyuzhuang assemblage provides rare but compelling fossil evidence recording the biological complexity of eukaryotic life evolved not long after their first appearance in geological records in the late Paleoproterozoic.