A sponge was among the exceptionally well-preserved fossils found at a site in Wales.

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Exceptionally well-preserved fossils of tiny worms, starfish, sponges, barnacles and other creatures with no modern parallel discovered at a quarry in Wales are painting a picture of life on Earth 462 million years ago.

A fossilized worm with its gut preserved.

It was a critical time in the planet’s history when there was virtually no life on land, but animals and algae were thriving in the seas.

The Castle Bank fossil site near Llandrindod Wells in Powys is remarkable because of the time period it captures and because the fossils show soft tissue such as eyes, nerves, the gut and brain that are preserved as films of carbon in mudstone, according to a new paper published in the journal Nature Ecology & Evolution on Monday.

The site gives a fuller picture of the variety of life in the deep past — not just the animals with hard shells and bones that are usually found as fossils.

Joseph Botting, study author and honorary research fellow at Amgueddfa Cymru Museum Wales, had first spotted a sponge at the site in 2013 and collected some similar fossils over the years — but he hadn’t conducted an in-depth study on the site.

In April 2020, with time afforded by a Covid-19 lockdown, he went back to the fossil site, which is near his home, and he discovered a piece of rock “which had things with tentacles in.”

Researchers Dr Lucy Muir, left, and Dr Joseph Botting worked together on the site in Wales.

“I basically didn’t sleep that night. As soon as you find that sort of level of soft tissue you know that anything could fossilize. So at that point we knew it was going to be important,” he said.

The fossils come from a period of time known as the Ordovician when life was becoming more complex. The earlier Cambrian period witnessed the origins of animals but by the end of the Ordovician period, Earth was home to more varied and diverse ecosystems.

Most of the 170 animals discovered so far from the fossil site were tiny (1-5 millimeters) and many were either completely soft-bodied when alive or had a tough skin or exoskeleton. The vast majority appear to be completely unknown species.

A fossilized starfish found at the site.

While other soft bodied creatures from the past have preserved in a similar way, most notably in the Burgess Shale deposits in the Canadian Rockies in British Columbia, Castle Bank dates from 50 million years later in the Middle Ordovician.

“There’s no comparable site of the same age. It’s a completely unique site,” said Lucy Muir, study coauthor and also an honorary research fellow at Amgueddfa Cymru Museum Wales.

Muir and Botting, who are married, said they also wanted to highlight the contribution of their local community to the discovery. A crowdfunding project to buy microscopy equipment helped them identify the animals and understand the importance of the site.