This Trove of Fossils in Wales Is Revealing Secrets of Early Animal Life

Scientists have uncovered 170 species from around 462 million years ago, unveiling surprises about when tiny marine creatures evolved and disappeared

mix of modern and Cambrian sea life coexisting
Fossils in Wales reveal a glimpse into marine life 462 million years ago. In this illustration based on the new finds, the tall sponge in the foreground is less than one inch in height. Yang Dinghua / Nature Ecology & Evolution

Paleontologists have uncovered a trove of well-preserved fossils in Wales that date to around 462 million years ago. Already, scientists are speculating that this site could become as important to our understanding of Earth’s early life as some of the most famous fossil beds, like Canada’s Burgess Shale.

The findings, published Monday in the journal Nature Ecology & Evolution, could provide a window into some of the first groups of modern animals to evolve.

“It is wonderful,” Douglas Erwin, a paleontologist at the Smithsonian’s National Museum of Natural History who did not contribute to the study, tells Science’s Elizabeth Pennisi. There are “some beautiful specimens, including some surprising discoveries.”

“Every time we go back, we find something new, and sometimes it’s something truly extraordinary,” Joseph Botting, a paleontologist and co-author of the study, tells the Guardian’s Linda Geddes. “There are a lot of unanswered questions, and this site is going to keep producing new discoveries for decades. We’re excited to see what comes next.”

Called Castle Bank, the site dates to the Cambrian Period, when many of the groups of animals that exist today first appeared in the fossil record. At the start of this era, around 540 million years ago, a wide variety of life forms evolved in a relatively short span of time, so that period has been dubbed the Cambrian explosion.

But many of those Cambrian animals went extinct after that. By 400 million years ago, the fossil record is dominated by ancestors of modern animals instead, according to Science. Now, researchers are trying to better understand what happened in between.

The newly discovered fossils might contain hints to an answer, since they date to this period. “There’s no comparable site of the same age. It’s a completely unique site,” paleontologist and study co-author Lucy Muir tells CNN’s Katie Hunt.

Muir and Botting, who are married, first found fossils at the site in 2013, but they didn’t conduct an in-depth investigation of the area until the pandemic lockdowns in 2020, per CNN. Since then, they’ve uncovered around 170 tiny marine organisms, most of which are between one and five millimeters long. The animals have preserved soft tissues, including digestive systems, eyes and brains—a relative rarity in the fossil record, because hard body parts fossilize more easily.

Their findings include some animals that exist today, like worms, sponges, barnacles and starfish, per CNN. But they also found fossils that resemble some Cambrian creatures, like the five-eyed Opabinia that had a segmented proboscis, or the spiny, slug-like Wiwaxia.

The site “coincides with the Great Odovician Biodiversificaiton event, when animals with hard skeletons were evolving rapidly. I like to refer to it as ‘when life got interesting,’” Muir tells the Guardian. “It is when ecology diversified, as well as animals themselves.”

The study shows that during the biodiversification event, ancestors of modern animals and Cambrian animals overlapped. From the fossils, paleontologists are discovering that certain modern creatures likely arose earlier than expected, and various Cambrian species may have evaded extinction for much longer than thought.

“This is muddying the water,” Joanna Wolfe, a biologist at Harvard University who has previously studied the site but was not an author of the new study, tells Science. “A lot of the groups that are modern are surviving alongside those [early] things.”

Muir and Botting conducted their analysis using equipment they acquired thanks to a crowdsourcing effort that raised $20,000, per the Guardian.

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