Evolutionary pattern of fusulinacean foraminifer in Maokouan, middle Permian

A composite standard section (CSS) has been established for the Maokouan (≈ Guadalupian) in Guizhou Province, southwestern China, which includes stratigraphical ranges of 179 fusulinacean species from five sections of the Maokou Formation in this area. Based on statistical results of the first and last appearances of fusulinacean species in the CSS, three evolutionary radiations and four pulses of extinction, characterized by high rates of species origination and extinction significantly different from the rates of background evolution, are recognized in the Maokouan fusulinacean fauna. The evolutionary pattern of fusulinacean foraminifer suggests that the Maokouan mass extinction probably started at the middle Maokouan and dramatically intensified in the late Maokouan.