They discover a unique deposit of fossils that reveals primitive life forms

() — Exceptionally well-preserved fossils of tiny worms, starfish, sponges, crustaceans and other creatures unmatched today, discovered in a dig in Wales, are revealing what life was like on Earth 426 million years ago.

A fossilized worm with its intestine preserved. Credit: Courtesy of Joseph Botting

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

The Castle Bank fossil site, near Llandrindod Wells, Powys, is notable for the period it covers and because the fossils show soft tissues such as eyes, nerves, gut and brain that are preserved as carbon films in the muddy sandstone, according to a new study published this Monday in the academic journal Nature Ecology & Evolution.

The site offers a more complete picture of the variety of life in the deep past, not just the hard-shelled, bony animals that are often found as fossils.

Joseph Botting, study author and Honorary Research Fellow at the Amgueddfa Cymru Museum in Wales, had first seen a sponge at the site in 2013 and had collected a few similar fossils over the years, but had not conducted an in-depth study of it. the deposit.

In April 2020, with the time that the confinement due to covid-19 gave him, he returned to the fossil site, which is near his house, and discovered a piece of rock “that had things with tentacles inside.”

Researchers Dr. Lucy Muir, left, and Dr. Joseph Botting worked together at the Welsh site. Courtesy of Joseph Botting

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

The fossils come from a period known as the Ordovician, when life was becoming more complex. Animals originated in the Cambrian, but by the end of the Ordovician the Earth was home to more varied and diverse ecosystems.

Most of the 170 animals discovered so far in the fossil bed were tiny (1 to 5 millimeters) and many had completely soft bodies when alive or had tough skin or an exoskeleton. The vast majority appear to be completely unknown species.

Fossilized starfish found at the site. Courtesy of Joseph Botting

While other soft-bodied creatures from the past have been similarly preserved, most notably in the Burgess Shale deposits of the Canadian Rockies in British Columbia, Castle Bank dates to 50 million years later, in the Middle Ordovician.

“There is no comparable site of the same age. It is a completely unique site,” says Lucy Muir, co-author of the study and also an honorary researcher at the Amgueddfa Cymru Museum in Wales.

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