A sixth mass extinction that paved the way for the dinosaurs has been discovered by scientists.
It happened 233 million years ago – and began the rise of the biggest animals that ever walked the earth.
Massive volcanic eruptions in western Canada wiped out vast numbers of species on land and in the oceans – allowing them to take over.
They included a menagerie of lumbering beasts such as sheep-sized reptiles called rhynchosaurs and elephant-like tusked dicynodonts.
The disaster also massacred reefs, sea lilies, shelled octopuses and a group of marine reptiles called thalattosaurs.
The carnage during the middle of the Triassic period has been named the ‘Carnian Pluvial Episode’.
It led to extreme climate change and rerouted the trajectory of life on Earth – launching the near-eternal ‘age of the dinosaurs’.
Lead author Dr Jacopo Dal Corso, of the China University of Geosciences at Wuhan, 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 gigantic pulses erupted into the atmosphere from volcanoes whose frozen magma have been unearthed in Wrangellia province in British Columbia.
They fuelled violent storms, lashing rains, scorching temperatures – and ocean acidification.
The study published in Science Advances is based on a review of geological and palaeontological evidence from around the world.
It found huge volumes of volcanic basalt poured out – and forms much of the western coast of North America today.
Evidence of a very humid period around this time – and lasting about a million years – was first detected back in the 1980s.
It caused major biodiversity loss. New groups took over – forming more modern-like ecosystems.
The shifts in climate encouraged growth of plant life – and the expansion of modern conifer forests.
Co-author Professor Mike Benton, of Bristol University, 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.
“We now know 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.”
As well as dinosaurs, many modern groups of plants and animals also appeared including some of the first turtles, crocodiles, lizards – and mammals.
The Carnian Pluvial Episode also had an impact on ocean life – leading to the birth of modern-style coral reefs and plankton. It triggered changes in the chemistry and carbonate cycle of the seas.
Dr Dal Corso said: “So far, palaeontologists had identified five ‘big’ mass extinctions in the past 500 million yeas 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.”
The last happened 65 million years ago when a city sized space rock wiped out the dinosaurs.