Long ago, before the dawn of the age of dinosaurs, a heavy rain descended upon the supercontinent of Pangaea — and it kept raining for more than 1 million years.
This epic rainy spell — known now as the Carnian Pluvial Episode (CPE) — occurred roughly 233 million years ago and was a stark shift from the typically arid conditions of the late Triassic period. But stormy skies weren’t the only change Earth was facing. According to a study published Sept. 16 in the journal Science Advances, new fossil evidence suggests that the CPE was in fact a major extinction event — driven by volcanic eruptions and climate change — that resulted in the deaths of one-third of all marine species, plus a significant number of terrestrial plants and animals.
This “lost” extinction event doesn’t quite reach the death toll of the five major mass extinctions typically discussed by the scientific community (the Permian-Triassic extinction, which occurred just 20 million years earlier, may have wiped out 90% of living species, for example). However, the study authors argue, the CPE isn’t just important for what was lost — but also for what was gained. Far from just a period of death, the CPE was a period of “turnover,” the researchers wrote, effectively paving the way for the dominion of the dinosaurs and the evolution of many terrestrial animal groups that still roam the Earth today.