But this was just one of the Big Five mass extinctions the planet has experienced since living organisms evolved 3.5 billion years ago, and it wasn’t the worst.
Scientists now say they have found evidence of a new extinction event in the fossils that has allowed dinosaurs to dominate the Earth for more than 200 million years.
It took place 232 million to 234 million years ago and was called the Carnian pluvial episode.
“So far, paleontologists have identified five ‘major’ mass extinctions in the last 500 million years of life history,” said the study’s co-author. Jacopo Dal Corso, a geologist at the Chinese University of Geology in Wuhan, in a news statement.
“Each of them had a profound impact on the evolution of the Earth and life. We identified another major extinction and apparently played a key role in helping to restore life on land and in the oceans, noting the origins of modern ecosystems.”
The reason, the researchers say, is most likely massive volcanic eruptions in present-day Western Canada, where huge amounts of volcanic basalt have erupted 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 peaks in global warming,” Dahl Corso said.
Climate change has caused great losses of biodiversity in the ocean and on land. Just 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 – largely the evergreen trees we know today with needles and cones.
It wasn’t just dinosaurs. Many modern groups of plants and animals also appeared at this time, including some of the first turtles, crocodiles, lizards, and the first mammals.
The Carvian pluvial episode has also affected ocean life, with 33% of marine life missing, according to a study published in the journal Scientific Advances. This marks the beginning of the species of coral reefs observed today, as well as many modern plankton groups, suggesting profound changes in ocean chemistry after the mass extinction.
The warming climate is also associated with increased rainfall, and this was discovered in the 1980s as a humid episode lasting about 1 million years. But “the sudden dry conditions after the wet episode gave the dinosaurs a chance,” said study co-author Mike Benton, Professor of Vertebrate Paleontology at the University of Bristol in the United Kingdom in the statement.
“We already know that dinosaurs originated about 20 million years before this event, but they have remained quite rare and insignificant until the Carnian pluvial episode is hit,” Benton said.
Alfio Alessandro Chiarenza, a paleontologist and research associate at University College London, said that while the study highlighted many of the important changes that life had undergone during that time, he was “cautious in defining it as mass extinction”.
“Given the unevenness of fossil data, our information on trends in biodiversity over time and space is often uneven,” he said in an email.
“Fossils can be ‘hidden’ in rocks that we haven’t explored yet or just haven’t survived to this day,” he added.
Scientists usually define mass extinction as the extinction of at least 50% of all species in a short time. Geologically, this period of time it is usually less than 2.8 million years old.
Benton told CNN that they could not yet calculate a figure for the loss of terrestrial life, but the event would affect plants and animals with very different ecologies around the world and with significant loss of species in a short period of time.
The worst mass extinction occurred 250 million years ago, destroying 95% of all species and probably due to massive volcanic eruptions in Siberia.