Treasure trove of fossils found in lockdown

One of the world's most important fossil deposits has recently been found in Wales. Husband and wife team, Dr Joseph Botting and Dr Lucy Muir, made the discovery during the pandemic lockdown.

Joe - Almost all of the fossil record misses the vast majority of animals because you only get fossilized, the bits that are the heart, the minimal shells, the bones, the teeth, that sort of thing. But there are very, very few places around the world where you can get by some sort of fluke of chemistry, the preservation of soft tissues, entire animals, extremely delicate structures. And we stumbled across a site like this near our home.

Chris - Lucy, how did the two of you find this? Was this just at one of those lockdown walks?

Lucy - Well, we actually found the site about 10 years ago and had done a bit of work there collecting fossil sponges, which is what Joe worked on. And then it came to the lockdown. Joe thought, 'oh, I'll go and get a few more specimens from that quarry, then I can write that up'. So he went out, hammered some rocks and found a little worm tube with tentacles coming out. And at that point we knew there was a lot more there than just sponges.

Chris - And Joe, the quality of what you've got, is it because the preservation is so good that you've got insights at very, very detailed levels? Or is it just that there's such a huge diversity there? Or is it both?

Joe - It's both. Yeah. We have something like 170 species we think so far. But the point is it's everything. So we don't seem to be missing any major parts of the ecosystem. We've got everything from tiny little worms to little crustaceans to strange tentacle monsters. Mostly they're just one or two millimetres along, but the detail within them is absolutely stunning. And it goes down to the micron scale. So a thousandth of a millimetre resolution in some of the features that we're seeing. We've got the little arthropod that's two millimetres long and preserves its brain and its optic nerve and the eye, and another one with a gut that's 20 microns wide, 20000th of millimetre. It's just extraordinary.

Chris - You mentioned Lucy and Joe, the fact that these are very, very small. I was staggered when I read your paper to learn that although you are honorary academics at a nearby institution, you basically had to crowdfund to buy a microscope to do this work. You've done this as almost citizen scientists.

Lucy - Yes, that's right. We very soon realized that our small adequate microscope just couldn't visualize the things that we were finding. So we actually tried crowdfunding to get a good microscope and a good camera, and people were incredibly generous. And we raised £18,000 and got two microscopes and two good cameras. So we can actually photograph the fossils, we can publish papers about them so that everyone knows about them.

Chris - That's a microscope each, isn't it? Fantastic. And Joe, this assemblage that you've got dates from about 462 million years ago, what is the importance and relevance of that point in the timeline?

Joe - Yeah, this is an interval which is very important in the evolution of life. It's before the origin of land plants, before there was anything living on land, but after a period called the Cambrian, when we have a lot of these foreigners that tell us how the first animals got going, but it's in a sort of gap in the record where we know life was diversifying spectacularly. The ecosystems were getting much more complex, but we only really know that from the 'shelly' fossils, the brachiopods and trilobites. So this falls into this gap and fills in a huge hole in our knowledge. Because it's telling us what all the soft bodied animals were doing at the same time.

Chris - And Lucy, do you know why what you've found is there, as in why it's been so well preserved and why you've, you've still got it for you to find today?

Lucy - The short answer is that's some of the work we're going to be doing over the next few years. We've got some ideas. We know that the animals that became the fossils were buried alive probably by sediment lumps. And we think there might be something a bit odd about the seawater chemistry because we don't normally see this type of soft tissue preservation at this age. So the area was a volcanic island complex. So we think maybe all the volcanic activity made the seawater chemistry a bit odd and that somehow allowed things to become preserved that would normally just have rotted away.

Chris - In your paper, Joe, you point out a lot of the animals are juveniles. So is it that this is just the right place for young animals to be reared? Is that why you think that that volcanic island complex is got so many juveniles in there or is there some other reason why they're so heavily represented here?

Joe - It's actually very difficult to interpret this because there's only one species that we can be sure of. We are looking at juveniles and that's a trilobite that normally gets up to about six centimetre long and here it gets up to five millimetres. Everything else, including a lot of these strange soft body things, are actually the same sort of size, a millimetre or two, as they are in the modern day and much smaller than they were in the Cambrian before it. So we think that possibly an ecosystem maybe attached to undersea boulders and so on, where you have a small sort of forest, if you like, of little encrusting creatures. And only small animals could really fit into the ecological niches there. So the adult trilobites were off living somewhere else, but they left their juveniles to grow up there. But we don't know at this stage whether a lot of the other small crustaceans and so on were juveniles or whether they're actually adults of the same sort of size as they are today. It's going to be quite hard to work that one out. We're just going to need a lot more fossils.