• Extinction;
  • Fusulinaceans;
  • Middle Permian;
  • Southwest China

Study of the extinction process of 179 fusulinacean species belonging to 34 genera in southwest China demonstrates that diversity changes in the small (shell length ≤6 mm) and large (shell length >6 mm) species groups were very similar throughout the ‘Maokouan’ (∼Guadalupian). However, significant differences in the timing of extinction pulses occur between different fusulinacean clades with different wall structures, i.e. the nankinellids, schwagerinids, verbeekinids and neoschwagerinds, and between the large and small species groups within the schwagerinids and verbeekinids. Fusulinacean diversity reveals that the Guadalupian mass extinction began in the Middle ‘Maokouan’ and greatly intensified in the late ‘Maokouan’. With only seven species of five genera surviving into the Late Permian, the extinction of fusulinaceans in the Guadalupian mass extinction is 96% at species level and 85% at generic level in southwest China. The preferential extinction of large, morphologically complicated species and the survival of simpler, ecologically more tolerant species of the nankinellids suggest that the extinction of Guadalupian fusulinaceans was caused by falling sea level and the consequent effects related to salinity, temperature and substrate changes. It is also demonstrated that biological characters of fusulinaceans such as shell size and test structures could have certain effects on survivorship of species in the early stages of mass extinction when extinction pressure was less intensive but were ineffectual during the extinction climax.