Han Zeng
By Ian Randall
Deputy Science Editor
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A treasure trove of exceptional fossils from 512 million years ago—including 90 species previously unknown to science—is shining light on a mysterious page in the history of life.
Paleontologists unearthed the haul, dubbed the ‘Huayuan biota’ from a quarry in Hunan province, southern China, during field trips between 2021 and 2024.
Comprising a total of 153 different species from 16 major animal groups—including sponges, arthropods and bizarre, segmented apex predators known as radiodonts—the Huayuan biota makes up a complex food web, say the researchers.
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The discoveries date back to the wake of a mass extinction known as the Sinsk event, which was driven by a deadly drop in the oceans’ dissolved oxygen 513.5 million years ago.
The Sinsk event brought an end to the sudden increase of complex life that began some 540 million years ago in what geologists call the "Cambrian explosion."
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Spanned from 541 to 485 million years ago, the Cambrian period began with one of the most significant evolutionary events of Earth’s history, during which nearly all of the major animal phyla began appearing in the fossil record in what is oft-dubbed the "Biological Big Bang."
Most of what we know about Cambrian life comes from the discovery of fossil deposits that formed under special conditions that allowed them to be exceptionally well-preserved, even recording soft tissue parts that would normally be lost to the geological record.
The premier example of these Cambrian "Konservat-Lagerstätten" (literally: "preservation deposits") is the Burgess Shale, a 508 million-year-old rock unit from the Canadian Rockies.
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A problem is that the Burgess Shale postdates the Sinsk event by some 5.5 million years; the other two high-quality fossil deposits (the Chengjiang and Quinjiang biota of China), meanwhile, predate the mass extinction.
Because of this, the exact impact of the Sinsk event—which is thought to have had extinction rates in the order of 41 to 49 percent—has been unclear.
"The rarity of deposits bearing high-diversity Burgess Shale-Type boots has restricted our understanding of the evolutionary and ecological dynamics of the Cambrian explosion," paleontologist professor Han Zeng of the Nanjing Institute of Geology and Palaeontology and his colleagues explain in their paper.
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Comparison between the Huayuan biota and 45 other Cambrian fossil deposits from around the globe have revealed strong links between the newly-discovered Lagerstätte and the younger Burgess Shale deposits of North America.
This, the researchers said, suggests that Cambrian life was dispersed long distances across the oceans by factors including currents and sea-level changes.
The paleontologists also report that deep-water environments such as that preserved by the Huayuan biota were less affected by the Sinsk event that their shallow-water counterparts, and perhaps served as refuges for life or sites of evolutionary innovation.
Do you have a tip on a science story that Newsweek should be covering? Do you have a question about the Cambrian Explosion? Let us know via science@newsweek.com.
Reference
Zeng, H., Liu, Q., Zhao, F., Luo, C., Wang, D., Zhu, Y., Liu, Y., Chen, K., Sun, Z., Hong, Y., Miao, L., Hu, C., Sun, H., Pan, B., Zhao, J., Yin, Z., Li, G., Yang, X., Yang, A., Hu, S., & Zhu, M. (2025). A Cambrian soft-bodied biota after the first Phanerozoic mass extinction. Nature.https://doi.org/10.1038/s41586-025-10030-0
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