The Permian-Triassic extinction event, occurred at about 252 MYA. This period marks the boundary between the Permian and Triassic periods.
It is the most severe extinction event that took place on earth, with up to 96% of all marine species and 70% of terrestrial vertebrate species becoming extinct.
Due to such a great biodiversity loss, the recovery of life on Earth took a longer time than other extinction events.