A new study led by our Earth Sciences department has made a surprising discovery about a mysterious fossil from the Cambrian period — over 500 million years ago.
The fossil, Shishania aculeata, was originally thought to be an early mollusc, a group that includes snails and clams. But new research shows that it is actually a sponge-like animal known as a chancelloriid.
This finding, published in the journal Science, changes our understanding of how some of the earliest animals evolved.
The fossil of Shishania was first discovered in southern China and was thought to have a foot-like structure and protective spines, features that led scientists to believe it was related to molluscs.
However, the new study shows that many of these features were the result of how the fossil was preserved, not the animal’s actual anatomy.
When the researchers looked at better-preserved fossils, it became clear that what looked like a foot was just the inside of the animal that had split open. Its body is more like a spiny bag than a mollusc.
The research team’s new fossils show that Shishania shares many features with chancelloriids, which are strange, bag-shaped animals that lived fixed to the sea floor and had no head, mouth, or organs.
Their bodies were covered in hollow spines, possibly used for defence.
This discovery helps fill in a gap in the fossil record and shows how chancelloriids may have evolved more complex body shapes over time.
Understanding Shishania helps scientists learn more about the early ‘Cambrian explosion,’ a time when many animal groups first appeared.
It also shows how fossil evidence can be misread and how new discoveries continue to reshape what we know about life’s early history.
Fossils like Shishania remind us that evolution is full of surprises and a great example of how science constantly improves our understanding of the natural world.
Our Department of Earth Sciences is ranked in the top 100 in the QS World University Rankings by Subject 2025. Visit our Earth Sciences webpages for more information on our undergraduate and postgraduate programmes.
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