Researchers have unearthed a remarkable fossil site in southern China that preserves a 512-million-year-old marine ecosystem from the Cambrian period. The find, known as the Huayuan biota, offers insights into life after the Sinsk extinction event around 513.5 million years ago. It includes thousands of fossils, many previously unknown to science.
In 2021, Han Zeng and colleagues from the Nanjing Institute of Geology and Palaeontology began excavating a quarry in Huayuan County, Hunan Province. Their efforts have yielded 8,681 fossils representing 153 species, with nearly 60 percent being new discoveries. This assemblage, dubbed the Huayuan biota, captures 16 major animal groups that inhabited deep ocean environments, which were less severely affected by the Sinsk event—a mass extinction that drastically lowered ocean oxygen levels and primarily devastated shallow-water habitats.
The fossils predominantly feature arthropods, akin to modern insects, spiders, and crustaceans, alongside molluscs, brachiopods, and cnidarians related to jellyfish. Among the standout specimens is the 80-centimeter-long arthropod Guanshancaris kunmingensis, likely the apex predator of this ancient community. Notably, the genus Helmetia, previously known only from Canada's Burgess Shale, appears here, suggesting early animals dispersed vast distances—possibly via larval transport in ocean currents.
Exceptional preservation stems from rapid burial in fine mud, revealing intricate details like walking legs, antennae, gills, pharynxes, guts, eyes, and neural tissues in soft-bodied organisms. As Zeng explains, prior understanding of the Sinsk event relied on skeletal fossils such as trilobites and sponge reefs; the Huayuan site enriches this picture with soft-bodied diversity.
Experts praise the discovery's significance. Joe Moysiuk of the Manitoba Museum notes it provides 'critical snapshots' of Cambrian biodiversity amid the extinction. Tetsuto Miyashita of the Canadian Museum of Nature compares it to famed sites like China's Chengjiang biota (520 million years old) and the Burgess Shale (508 million years old), highlighting how it disentangles influences of geography, extinction, and ocean chemistry. Intriguingly, fish are absent so far, prompting questions about their scarcity post-extinction. Zeng's team continues analyzing material, anticipating further revelations, including potential fish fossils.
The findings, published in Nature (DOI: 10.1038/s41586-025-10030-0), position Huayuan as a premier Cambrian site, rivaling or surpassing the Burgess Shale in scope and quality.