The species, Fuxianhuia protensa, is an extinct arthropod that roamed the seafloor about 520 million years ago. It would have looked something like a very simple shrimp."Each of the fossils found at Chengjiang Shales -- fossil-rich sites in southwest China -- revealed F protensa's ancient brain looked a lot like a modern crustacean's," said Nicholas Strausfeld, a Regents' professor in the department of neuroscience at the University of Arizona.

He and his team found that the brains were preserved as flattened carbon films. This led the research team to a convincing explanation as to how and why neural tissue fossilises. The only way for an object to be fossilised is for it to be rapidly buried.

Hungry scavengers cannot eat a carcass if the brain is buried faster and as long as the water lacks in oxygen so a buried creature's tissues escapes being consumed by bacteria as well. Strausfeld and his collaborators suspect F protensa was buried by rapid, underwater mudslides -- a scenario they experimentally recreated by burying sandworms and cockroaches in mud.

According to Strausfeld, the brain withstood the pressure from being rapidly buried under thick mud because the nervous system must have been remarkably dense.

Strausfeld is now working to elucidate the origin and evolution of brains over half a billion years in the past."People, especially scientists, make assumptions. The fun thing about science, actually, is to demolish them," Strausfeld noted in the paper published in the journal Current Biology.



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