By: Ellie Zhang

A tiny but ancient worm, called Youti yuanshi, has been uncovered by researchers in Durham University.

Scientists were shocked since it is almost impossible for an organism that small and fragile to maintain its existing state.

It dates back 520 years ago– to the Cambrian period, when today’s animals were first evolving.

The worm belongs to a group called arthropods, consisting of modern insects, crabs, centipedes, and spiders.

Dr. Martin Smith, who had published a research article on the baby worm, or larva, said that they only had adult fossils around this time, so getting a young one is considered a “scientific treat”.

“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?”

Dr. Smith and his research team in Durham University made detailed 3D images of the worm’s internal body, using special equipment from a professional facility in Harwell, Oxfordshire.

The facility, known as Diamond Light Source Facility, helps scientists produce severe beams of light which makes the organs visible.

The brain and nerves of the larva were still intact. Dr. Smith says they can now figure out how insects are able to develop such complex brains.

Dr Smith said: “When I used to daydream about the one fossil I’d most like to discover, I’d always be thinking of an arthropod larva.”

Their complicated heads allow arthropods to become the dominant organisms in the Cambrian oceans.

The ancient 500-year-old fossil, a very rare discovery, fills an important gap in our understanding of how our early ancestors developed and became so successful during the Cambrian Explosion of life.