Fake animal fossil debunked: Earth's oldest group are really seaweeds

Thanks to unusually preserved soft tissue, researchers have reached a new identification.
Nergis Firtina

A recent study led by Durham University, Yunnan University, and Guizhou University has recently shown that a group of ancient sea creatures is not as old as previously believed. Their earliest fossils are actually seaweeds.

This indicates that bryozoans, which had tentacles and lived in underwater colonies like marine skyscrapers, are much more recent than previously believed, first emerging during the Ordovician epoch (480 million years ago), says the press release.

Fake animal fossil debunked: Earth's oldest group are really seaweeds
Mineralised fossils of Protomelission gatehousei from Wirrealpa, Australia.

As a result, they are the only group of fossil animals that did not participate in the 40 million-year-old Cambrian explosion, a rapid period of evolution. The delayed appearance of bryozoans demonstrates that, contrary to popular belief, evolution proceeded to sculpt new body designs over a considerably more extended period than the Cambrian, says the press release.

“We tend to think of the ‘Cambrian explosion’ as a unique period in evolutionary history, in which all the blueprints of animal life were mapped out,” said study co-author Dr. Martin Smith of the Department of Earth Sciences, Durham University.

“Most subsequent evolution boils down to smaller-scale tinkering on these original body plans. But if Bryozoans truly evolved after the Cambrian period, it shows that evolution kept its creative touch after this critical period of innovation – may be the trajectory of life was not set in stone half a billion years ago,” he added.

Fake animal fossil debunked: Earth's oldest group are really seaweeds
The field site.

Protomelission gateshousei, formerly thought to be the first Bryozoan, was discovered to have hitherto unobserved soft parts in ancient fossil material found in the hills of China. Because of this delicate tissue, the researchers identified Protomelission as a member of the green algae family Dasycladales.

“Where previous fossils only preserved the skeletal framework of these early organisms, our new material revealed what was living inside these chambers," explained study co-author Professor Zhang Xiguang of Yunnan University."

“Instead of the tentacles we would expect to see in Bryozoans, we discovered simple leaf-like flanges – and realized we were not looking at fossil animals, but seaweeds. This means that the oldest convincing Bryozoan fossils do not evolve until the next geological period, the Ordovician.”

This study was supported by the National Natural Science Foundation of China and was published in Nature.

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