"the Earth's most severe known extinction event, with up to 96% of all marine species[6][7] and 70% of terrestrial vertebrate species becoming extinct.[8] It is the only known mass extinction of insects.[9][10] Some 57% of all families and 83% of all genera became extinct. Because so much biodiversity was lost, the recovery of life on Earth took significantly longer than after any other extinction event,[6] possibly up to 10 million years"

https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extin...

Maybe it's methane, maybe not.