Olson's Extinction was a mass extinction that occurred 273 million years ago in the late Cisuralian or early Guadalupian epoch of the Permian period, predating the much larger Permian–Triassic extinction event.[1][2][3] The event is named after American paleontologist Everett C. Olson, who first identified the gap in fossil record indicating a sudden change between the early Permian and middle/late Permian faunas. Some authors also place a hiatus in the continental fossil record around that time,[4][2] but others disagree.[5][6][7][8][9] This event has been argued by some authors to have affected many taxa, including embryophytes, marine metazoans, and tetrapods.