The dawn of the Phanerozoic: A transitional fauna from the late Ediacaran of Southwest China

Animal diversification across the Ediacaran-Cambrian transition was a crucial event in Earth history, fundamentally altering our planet and its biosphere. However, Ediacaran fossil assemblages show limited overlap with those from the Cambrian, obscuring the critical interval when the animal phyla were diversifying. We report a new terminal Ediacaran fossil assemblage preserved as carbonaceous films from the Jiangchuan Biota, Yunnan, Southwest China. This assemblage diverges from coeval sites, preserving Ediacaran body fossils alongside recognizable nonbilaterians and bilaterian body and trace fossils. These include diverse vermiform animals and the oldest deuterostomes (stem-group ambulacrarians). Our discovery provides insight into the radiation of Bilateria, the most diverse and disparate animal clade.