But it was only one of the Big Five mass extinctions the planet has undergone since living organisms evolved 3.5 billion years ago, and it wasn’t the worst.
Now, scientists say they have identified evidence of a new mass extinction event in the fossil record, which allowed dinosaurs to dominate the Earth for over 200 million years.
He takes his place From 232 million to 234 million years ago and was called the Carnian rain episode.
“So far, paleontologists have identified five ‘great’ mass extinctions in the last 500 million years of life history,” said study co-author. Jacopo Dal Corso, a geologist at the China University of Geosciences in Wuhan, in a statement.
“Each of these has had a profound effect on the evolution of Earth and life. We have identified another major extinction event, and it evidently played an important role in helping restore life on land and in the oceans, marking the origins. of modern ecosystems. “
The cause, the researchers said, was most likely massive volcanic eruptions in what is now western Canada, where huge volumes of volcanic basalt spilled and eventually formed much of the west coast of North America.
“The eruptions were so huge, they pumped huge amounts of greenhouse gases like carbon dioxide, and there were spikes in global warming,” Dal Corso said.
Climate change has caused severe biodiversity loss in the ocean and on land. Immediately after the extinction event, new groups took over, forming more modern ecosystems. Climate change has encouraged the growth of plant life and the expansion of coniferous forests, the largely evergreen trees we know today with needles and cones.
It wasn’t just the dinosaurs. Many modern groups of plants and animals also appeared around this time, including some of the earliest turtles, crocodiles, lizards, and the earliest mammals.
The Carnian rain episode also had an impact on ocean life, with 33% of marine life disappearing, according to the study, published in the journal Scientific Advances. It marked the beginning of the type of coral reefs seen today, as well as many of the modern plankton groups, suggesting profound changes in ocean chemistry following the mass extinction event.
Warming of the climate was also associated with increased rainfall, and this was detected in the 1980s as a wet episode lasting about 1 million years in all. But it was “the sudden arid conditions after the wet episode that gave the dinosaurs their chance,” said study co-author Mike Benton. professor of vertebrate paleontology at the University of Bristol in the UK in the statement.
“We now know that dinosaurs originated about 20 million years before this event, but they remained quite rare and of little significance until the Carnian rain episode,” Benton said.
Alfio Alessandro Chiarenza, a paleontologist and associate researcher at University College London, said that while the study highlighted many of the important changes life has undergone during this time frame, he was “cautious about defining this as an extinction of mass”.
“Given the irregularity of the fossil record, our information on trends in biodiversity over time and space is often patchy,” he said via email.
“Fossils may be ‘hiding’ in rocks that we have not yet studied or that simply have not been preserved to this day,” he added.
Scientists typically define a mass extinction as the disappearance of at least 50% of all species in a short amount of time. Geologically speaking, that time period it is usually less than 2.8 million years old.
Benton told CNN that they could not yet estimate a figure for the loss of terrestrial life, but the event would affect plants and animals of very different ecologies around the world and with a substantial loss of species in a short amount of time.
The worst mass extinction event occurred 250 million years ago, wiping out 95% of all species and was likely due to massive volcanic eruptions in Siberia.