PALEOBIOLOGICAL MODELS FOR THE PERMIAN-TRIASSIC EXTINCTION AND RECOVERY: PAST, PRESENT AND FUTURE (Invited Presentation)

The most significant mass extinction event of the Phanerozoic is enjoying unprecedented levels of scientific interest. In part, this can be traced to the 2001 ratification of the GSSP in Meishan, China, and to technological advances in areas such as geochemistry and geochronology. Arguably the most significant reason the close association of severe biotic crisis and elevated CO₂ levels during the Permian-Triassic (P-Tr) interval, which echo current trends in global warming and biological crisis. The P-Tr fossil record is an archive of data recording a global natural experiment of biosphere response to global warming that may help to frame debates concerning near-future scenarios. Deciphering the P-Tr fossil record is not straightforward, however, and a number of paleobiological models exist. Broadly, they may be grouped into those that simply utilize taxon range data and richness estimates, and those that invoke a more paleoecological or holistic approach combining several parameters. Different models seek to address different questions, with earlier ones mostly addressing the largest temporal and spatial scales (i.e. global, stage-level studies), whereas more recently others have been developed and applied at more local scales providing powerful tools for comparing recovery dynamics between depositional settings or geographic regions. Some enable different events to be compared, including comparisons between the past extinction intervals and recent, smaller-scale crises. All models face problems when the rock and fossil record varies significantly, as it does through the P-Tr interval, even when attempts are made to take sampling biases into account. The incorporation of better facies and paleoenvironmental data is a key challenge. Robust cladistic phylogenies, which may offer insights into clade-level recovery while minimizing stratigraphic issues, are available for vertebrates but are mostly lacking for P-Tr invertebrate groups. Models continue to be tested and refined, and a crucial remaining challenge is to collect quality data from regions of the world that are currently under-studied. The collection of high quality local paleoecological data will enable integration with ecosystem models used by ecologists and biologists, and should provide additional insights into the fossil record.