Experts from Durham University in England and Yunnan and Guizhou Universities in China have revealed in their research that the fossils that were previously thought to be the oldest bryozoans are actually green algae. It is millions of years younger than previously thought and appeared only in the Ordovician period (480 million years ago).

This makes them the only group of animal fossils that did not appear in the Cambrian “explosion,” a burst of rapid evolution 40 million years ago. The delayed emergence of bryophytes suggests that the Cambrian was not the only innovation period considered; instead, evolution continued to shape new body plans for a much longer period of time.

Ancient fossil found in Chinese hills reveals never-before-seen ‘soft pieces’ Protomelission gateshouse, previously considered the oldest bryophytes. This fragile texture allowed the researchers to interpret Protomelission as a member of the Dasycladales green algae group. Dr Martin Smith of Durham University’s Department of Earth Sciences, co-author of the study, said: “We tend to think of the ‘Cambrian Explosion’ as a unique period in evolutionary history when all animal life plans were mapped outwardly.

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“Most of the later evolution was a smaller-scale revision of these original body plans. But if bryophytes evolved after the Cambrian period, this suggests that evolution retains its creative touch beyond this critical period of innovation – perhaps life’s orbit wasn’t made of stone half a billion years ago.

“Instead of the tentacles we expected to see in bryozoans, we found simple leaf-like flanges and realized that these were seaweed, not fossil animals. This means that the oldest convincing bryozoan fossils did not develop until the next geological period, the Ordovician.”

The researchers suggest that the humble seaweed played a larger role in the early oceans than previously thought, although the origin of the animal groups was not so abrupt.