Fossil site in China reveals bevy of complex creatures lived prior to the Cambrian explosion, including a ‘Dune’-like sandworm
A newly discovered trove of fossils in southwest China is changing the timeline of the evolution of complex animals.
The diversity and complexity of animal life is thought to have increased rapidly around 539 million years ago, during an evolutionary explosion known as the Cambrian explosion. But the new fossil site suggests that some of this complexity was already present several million years before the Cambrian explosion, at the end of the Ediacaran period (about 635 to 539 million years ago).
“One specimen looks a lot like the Dune sandworm,” study co-author Frankie Dunna researcher who studies Ediacaran organisms at the University of Oxford’s Natural History Museum, said in a statement statement.
Some simple multicellular creatures, such as sponges, first appeared during the Ediacaran period. But most modern animal phyla arose during the Cambrian explosion that lasted between 13 and 25 million years ago, including chordates, the phylum that includes humans and other vertebrates.
The new fossil discovery suggests that some of this complexity had already appeared by the end of the Ediacaran. Discovered as part of the Jiangchuan Biota Fossil Collection in southwest China, the collection contains more than 700 fossilized animal and algae specimens dating from between 554 million and 539 million years ago. The researchers reported their results on Thursday April 2 in the journal Science.
“When we first saw these specimens, it was clear that these were something totally unique and unexpected,” study co-author. Luc Parrypaleobiologist at the University of Oxford, said in the release.
The fossils from this site are mostly flat imprints of the organism on the surrounding rock, called carbonaceous films. Unlike the three-dimensional imprints left by durable parts of the body, such as bones and shells, carbon films capture some details of the organism’s soft tissues, such as its intestines and mouthparts.
This less common method of preservation could help explain why scientists have so far not found evidence of these more complex animals in the Cambrian.
“Our results indicate that the apparent absence of these complex animal groups at other Ediacaran sites may reflect differences in preservation rather than a true biological absence,” co-author of the study. Ross Andersona researcher who studies the evolution of complex life at the University of Oxford’s Natural History Museum, said in the release. “Carbonaceous compressions like those at Jiangchuan are rare in rocks of this age, meaning similar communities may simply not have been preserved elsewhere.”
Gaorong Li et al. ,The dawn of the Phanerozoic: a transitional fauna from the late Ediacaran of southwest China. Science392,63-68 (2026). DOI:10.1126/science.adu2291
