Strange-looking fungus that grew nearly twice as high as a double-decker bus used to dominate what is now the Welsh landscape. Due to a discovery made just outside Cardiff, scientists have found that the huge phallic-shaped fungi, called Prototaxites, went up in flames due to a huge wildfire hundreds of millions of years ago.
A study by palaeobotanist Dr Ian Glasspool recently uncovered ancient mudstone that contained tiny fragments of charcoal, dating back to the Silurian period around 430 million years ago. Scientists believe that the charred remains are from a huge forest of the "funky" giant fungi with very few other plants growing on land at that time.
The charcoal fragments are the oldest evidence of wildfire ever recorded, with previous findings dated back to around 420 million years ago. Get the latest news from across Wales sent straight to your inbox for free by signing up to our newsletters.
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Appearing on the BBC World Service's Science in Action, Dr Glasspool, a research scientist at Colby College in Maine, said the huge Prototaxites "dwarfed the landscape" with the surrounding vegetation being very small. He added that the fungi could weigh as much as a large elephant.
"The Silurian vegetation was very different to what it is today," he said. "There were no woody plants at this time; most of the vegetation was very small. However, there was one giant that dwarfed the landscape, a very enigmatic fossil called Prototaxites.
"It grew anything up to eight metres in height, and about a metre in diameter. A sort of funky, humongous fungus; erect, very phallic structures; pillars of fungus that could weigh up to 10 metric tonnes."
Having already discovered similar evidence of wildfire in southern Poland, Dr Glasspool and his team drilled out the mudstone from deep underground in Rumney, a few miles outside central Cardiff. After it was uncovered, they found tiny fragments of charcoal between two and three milimetres in length laid down in the sediment.
The fragments were found to be from a near-shore marine setting and were being washed out to sea. However, as they left their mark in the mudstone, it is likely that the wildfires that broke out among the fungi forest were widespread.
It is hoped that the discovery will help scientists to understand more about how much oxygen was in the atmosphere hundreds of millions of years ago. With at least 16% atmospheric oxygen thought to be required for fires to spread, it is likely that this amount was present during the Silurian era, albeit less than the 21% concentration in the air today.
"For fires to propagate, you really need three things," Dr Glasspool told the BBC. "A source of fuel, which, surprisingly, we seem to have in sufficient amounts in the Silurian; you need a source of ignition, which is lightning strikes as the most likely source; and then you need at least 16% atmospheric oxygen.
"There are many geochemical proxy models that look at atmospheric oxygen, but there's quite a large discrepancy between many of them. So our charcoal data helps proof these models, and with enough data points, we can then get a better feel for how atmospheric oxygen was trending during this time interval."
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