Post‐Permian Radiation

Abstract

The post‐Permian radiation is the diversification of the modern evolutionary fauna in the aftermath of the end‐Permian mass extinction. This radiation was ‘delayed’ due to the magnitude of species loss, persistent environmental stress and subsequent biotic crises associated with the extinction event. Investigating the post‐Permian radiation is, however, confounded by issues with the quality of the Early Triassic fossil record. Since the low level of post‐extinction diversity has not been recorded since the Ordovician, an expectation is that the post‐Permian radiation would record large‐scale adaptations and the evolution of novel body plans. Globally, however, the extinction did not cause a reduction in the number of ecological lifestyles, and the post‐Permian radiation was seeded by an ecological diverse group of survivors. Groups that radiated into vacant ecospace include the bivalves, which diversified to dominate benthic habitats; the Scleractinia, which replaced the Palaeozoic reef‐building metazoans and the reptiles that became top marine predators. Our understanding of the post‐Permian radiation is hampered by the poor Early Triassic fossil record. The end‐Permian mass extinction event is the most severe extinction event known from the fossil record. The post‐Permian radiation was delayed due to ecological and environmental changes associated with the mass extinction event. The mass extinction did not cause the extinction of ecological lifestyles, and the post‐Permian radiation was at low taxonomic levels. The post‐Permian radiation caused a marked change in the evolutionary trajectory of almost all animal groups and led to fundamental changes in the functioning of marine ecosystems.