The Capitanian mass extinction event, also known as the end-Guadalupian extinction event,[2] the Guadalupian-Lopingian boundary mass extinction,[3] the pre-Lopingian crisis,[4] or the Middle Permian extinction, was an extinction event that predated the end-Permian extinction event. The mass extinction occurred during a period of decreased species richness and increased extinction rates near the end of the Middle Permian, also known as the Guadalupian epoch. It is often called the end-Guadalupian extinction event because of its initial recognition between the Guadalupian and Lopingian series; however, more refined stratigraphic study suggests that extinction peaks in many taxonomic groups occurred within the Guadalupian, in the latter half of the Capitanian age.[5] The extinction event has been argued to have begun around 262 million years ago with the Late Guadalupian crisis, though its most intense pulse occurred 259 million years ago in what is known as the Guadalupian-Lopingian boundary event.[6]