The
Permian–Triassic (
P–Tr)
extinction event, colloquially known as the
Great Dying or the
Great Permian Extinction, occurred about 252 Ma (million years) ago, forming the boundary between the
Permian and
Triassic geologic periods, as well as the
Paleozoic and
Mesozoic eras. It is the Earth's most severe known
extinction event, with up to 96% of all
marine species and 70% of
terrestrial vertebrate species becoming
extinct. It is the only known mass extinction of
insects. 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, possibly up to 10 million years.