Macroscopic carbonaceous compression fossils from the Tonian Liulaobei Formation in the Huainan region of North China

Macroscopic carbonaceous compression fossils are key to understand the early evolution of eukaryotes, explore the development of multicellularity, and strengthen the basis of biostratigraphic correlation during the Tonian Period (ca. 1000-720 Ma). Despite the potential geobiological importance of early macrofossils, the fossil record of Tonian macro-organisms is rarely documented. Here we describe an assemblage of diversified carbonaceous macrofossils from the Tonian Liulaobei Formation in the Huainan region, North China. In this study, we examine a large population of these macrofossils, clarify their taxonomy, and tentatively interpret their phylogenetic affinities. This assemblage consists of thirteen distinct morphotaxa, including eight genera and three new species, showing remarkable taxonomic diversity and domination of coenocytic macroalgae. The new data improve our knowledge about early Neoproterozoic biodiversity, and indicate a Tonian increase in morphological and taxonomic diversity of macrofossils compared to the Mesoproterozoic Era. This study also suggests that mac-roalgae may have begun to diversify and played a crucial ecological role in Tonian marine ecosystems.