Dubbed the Carnian Pluvial Episode, this major extinction event occurred some 233 million years ago. An international team of palaeontologists used interdisciplinary evidence including geology and fossil records to uncover the previously unknown mass extinction.
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The cause of the newly-identified event was volcanic eruptions of an unimaginable scale in Wrangellia Province, modern-day Canada.
It was the sudden arid conditions after the humid episode that gave dinosaurs their chance
Professor Mike Benton
This would have seen enormous quantities of volcanic basalt being spewed out, creating much of North America’s western coast in the process.
Professor Jacopo Dal Corso, of China University of Geosciences and lead author of the landmark study, said: “The eruptions peaked in the Carnian.
“I was studying the geochemical signature of the eruptions a few years ago and identified some massive effects on the atmosphere worldwide.
“The eruptions were so huge, they pumped vast amounts of greenhouse gases like carbon dioxide, and there were spikes of global warming”.
The rapid climate change resulted in a significantly wetter environment that lasted approximately one million years.
And this global warming led directly to the deaths of many animals and plants on land and sea.
However, one unanticipated consequence of this saw new forms of life rapidly taking over, forming more modern-like ecosystems.
This new-look environment encouraged the growth of plant life and the speedy expansion of modern conifer forests.
And Professor Mike Benton of University of Bristol’s School of Earth Science thinks this “switch” was key in advancing the rule of dinosaurs.
He said: “The new floras probably provided slim pickings for the surviving herbivorous reptiles.
“I had noted a floral switch and ecological catastrophe among the herbivores back in 1983 when I completed my PhD.
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“We now know that dinosaurs originated some 20 million years before this event, but they remained quite rare and unimportant until the Carnian Pluvial Episode hit.
“It was the sudden arid conditions after the humid episode that gave dinosaurs their chance.”
Dinosaurs were not the only group to benefit from this new epoch.
The researchers now recognise many modern groups of plants and animals also received a boost.
Such animals included the first turtles, crocodiles, lizards, and the first mammals.
Life in the oceans and seas was also affected by the Carnian Pluvial Episode.
Coral reefs recognisable to modern-day eyes and the first forms of plankton also arrived, suggesting ocean chemistry also underwent a profound change.
Professor Dal Corso believes the study is critical in understanding Earth’s ancient evolutionary history.
He said: “So far, palaeontologists had identified five ‘big’ mass extinctions in the past 500 million years of the history of life.
“Each of these had a profound effect on the evolution of the Earth and of life.
“We have identified another great extinction event, and it evidently had a major role in helping to reset life on land and in the oceans, marking the origins of modern ecosystems.”
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