Over 700 Fossils from China's Jiangchuan Biota Push the Origin of Complex Animals Back into the Ediacaran

An international team of paleontologists has described a trove of more than 700 fossils from southwestern China that fills one of the most significant gaps in the record of early animal life, according to a study published in Science on April 3, 2026. The site, known as the Jiangchuan biota in Yunnan Province, preserves organisms dating to between 554 and 539 million years ago, placing them squarely in the late Ediacaran period, at least four million years before the Cambrian explosion traditionally marked the dawn of complex animal diversity.

The discovery is the product of nearly a decade of fieldwork led by Professor Peiyun Cong and Associate Professor Fan Wei at Yunnan University. The fossils are preserved as carbonaceous films, a mode of preservation more commonly associated with celebrated Cambrian sites such as the Burgess Shale in Canada. This type of fossilization captures anatomical details that sandstone impressions, which dominate most Ediacaran sites, cannot retain. Feeding structures, guts, and locomotory organs are all visible in the Jiangchuan specimens, providing an unprecedented window into late Ediacaran anatomy.

Among the most consequential finds are fossils interpreted as the oldest known deuterostomes, specifically stem-group ambulacrarians, the lineage that today includes starfish, sea cucumbers, and acorn worms. Deuterostomes are the broader superphylum that also encompasses all vertebrates, including humans. Until now, the earliest body fossils of deuterostomes came from Cambrian deposits. The Jiangchuan material extends that record back into the Ediacaran for the first time, aligning body fossil evidence with molecular clock estimates that had long predicted an earlier divergence.

The assemblage also includes bilaterian worms exhibiting clear bilateral symmetry, early comb jellies, cnidarians resembling the previously described genus Haootia, and organisms displaying novel anatomical combinations that do not match any known species. The diversity suggests that the transition from Ediacaran to Cambrian faunas was more gradual than the abrupt shift implied by the term “explosion.”

Dr. Gaorong Li, who led the study while at Yunnan University and is now based at the Oxford University Museum of Natural History, stated that the discovery “closes a major gap in the earliest phases of animal diversification.” Associate Professor Luke Parry of the University of Oxford’s Department of Earth Sciences described the find as revealing a transitional community that bridges the Ediacaran and Cambrian worlds. Associate Professor Ross Anderson, also at Oxford, noted that the absence of such fossils from other Ediacaran sites may reflect differences in preservation conditions rather than the true biological absence of these organisms.

The study, titled “The dawn of the Phanerozoic: a transitional fauna from the late Ediacaran of Southwest China,” involved researchers from Yunnan University, the University of Oxford, and the Chinese Academy of Geological Science in Beijing. The findings add to a growing body of evidence that the Cambrian explosion was not the sudden genesis of animal complexity but rather the point at which preservation conditions improved enough to capture an evolutionary diversification already well underway.