Scientists stunned by the preservation of a 520-million-year-old worm larva with its brain intact

On the rare occasions we think about animal fossils, hard body parts such as bones, shells, and teeth usually come to mind first. Soft tissues generally decay soon after death, but not in the case of one remarkable discovery made by scientists.

The study, led by the University of Durham in England, examined a 520-million-year-old larva and found that its interior anatomy had been preserved with exceptional clarity. Researchers were even able to identify that its brain and digestive system remained intact, much to their amazement.

Advanced imaging reveals hidden anatomy

Using synchrotron X-ray tomography, a form of advanced scanning, researchers generated 3D images of miniature brain regions, digestive glands, a primitive circulatory system, and even traces of nerves supplying the larva’s simple legs and eyes, a press release explained.

“It’s always interesting to see what’s inside a sample using 3D imaging,” said study co-author Dr. Katherine Dobson. “But in this incredible tiny larva, natural fossilization has achieved almost perfect preservation.”

Insights into early arthropod evolution

The discovery could greatly improve understanding of how worm-like creatures developed into the sophisticated arthropod body plan. The preserved brain contains a structure called the protocerebrum, which scientists have found appears in different head formations, helping arthropods survive and thrive in a wide range of environments on Earth.

“When I used to daydream about the one fossil I’d most like to discover, I’d always be thinking of an arthropod larva, because developmental data are just so central to understanding their evolution,” said lead researcher Dr. Martin Smith. “When I saw the amazing structures preserved under its skin, my jaw just dropped – how could these intricate features have avoided decay and still be here to see half a billion years later?”

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