Unusually well-preserved fossils of more than 170 species from ‘when life got interesting’ 462million years ago have been unearthed in Wales, revealing soft tissues that include what could be a brain.

The remarkable find, made by Dr Joe Botting and Dr Lucy Muir at Castle Bank in Powys during the 2020 lockdown, will further understanding of animal evolution.

Fossils preserving soft tissues have primarily only been found dating back to the Cambrian period, around 541 to 485million years ago. The new find hails from the early Ordovician period, 485 to 470million years ago.

Described as Burgess Shale-type deposits, they are named after the location in Canada where such detailed fossils were first discovered.

The area reveals a rich and varied landscape of prehistoric life under the sea, mostly small marine organisms between 1mm and 5mm in length including worms, starfish, sponges, crustaceans and other arthropods – invertebrates with limbs and shells. 

While the exact location has not been disclosed, at the time the fossils were laid down the area was a volcanic island complex within the Welsh basin. It was part of the microcontinent of Avalonia in the temperate southern latitudes – far from the Wales of today.

At the time there was virtually no life on land, but beneath the waves was a different story.

‘I like to refer to it as “when life got interesting”,’ said Dr Muir, unveiling the rich find. ‘It coincides with the “Great Ordovician Biodiversification Event”, when animals with hard skeletons were evolving rapidly. For the first time, we will be able to see what the rest of the ecosystem was doing as well.’

‘There are some very important early Ordovician fossil sites,’ added Dr Botting, ‘but those are from much earlier, and entirely soft-bodied animals are rare even there. Here, it seems, we’ve got everything.’

Soft tissue so far identified includes the digestive systems of trilobites and what could be the eye, optic nerve and brain of an arthropod.

And while the preservation of soft tissues is unusual, many of the fossils found in the area are common for the type and age of rocks.

‘This means we’re looking at a normal marine ecosystem, in some sense, and therefore the soft-bodied fossils are probably also representative of the wider ecosystem at the time,’ added Dr Botting.

‘That said, the most common trilobite we only find as juveniles, suggesting that this precise area was being used as a nursery – so it wasn’t entirely typical.’

Among the species uncovered are new taxa yet to be classified, the fantastically-named wiwaxiids – slug-like molluscs covered in scales never yet seen after the Cambrian period – and surprisingly early examples of an Ordovician shrimp.

‘Every time we go back, we find something new, and sometimes it’s something truly extraordinary, said Dr Botting. ‘There are a lot of unanswered questions, and this site is going to keep producing new discoveries for decades. This is just the beginning, and we’re excited to see what comes next!’

The find is described by the team as a ‘real community effort’ after crowdfunding enabled the purchase of microscopy equipment required to carry out the research.

‘It wouldn’t have been possible for us to do it without the support of a large number of people,’ added Dr Botting. ‘Even most universities do not have the equipment that we were ultimately able to buy.’

The initial paper, published in Nature Ecology and Evolution, provides a general overview of the find – many more will follow describing the fossils and new species in detail.

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