Changes in terrestrial biota before the Permian-Triassic ecological crisis

The period around the Permian-Triassic boundary was marked by one of the most important and interesting events in the evolution of life. The diversity of both marine and continental biotas decreased. The changes were global and led to the establishment of the new Mesozoic World. Transformations of the organic world constituted a single process with changes in the inorganic components of the biosphere. The preceding glacial period had ended and the “cool,” zonal, and markedly seasonal climate was replaced by a “warm,” “equable,” virtually non-seasonal and azonal climate. The new climatic organization remained on Earth for more than two hundred million years. The biotic crisis was global: it involved the sea, the land, and inland waters. The changes on land began earlier and more superficial. The principal events were in the Kazanian and Vyatkian, before the end of the Permian. The crisis was caused to a greater extent by biospheric processes than by momentary external influences, the latter at most triggering the crisis.