THE IMPACT OF THE PERMO-TRIASSIC MASS EXTINCTION ON TERRESTRIAL AND MARINE BIOGEOGRAPHY (Invited Presentation)

The modern-day latitudinal diversity gradient (LDG) is a general trend of increasing biodiversity from the poles to the equator. However, our understanding of the underlying processes that drive it is limited, and it remains unclear whether this pattern was consistent throughout the Phanerozoic. One approach to answering these questions is to examine spatial biodiversity patterns in the geological past, across different global climate regimes and continental configurations.

The Late Permian–Middle Triassic (~260 – 237 Ma) represents an ideal time interval for investigating how LDGs respond to changing climates and landmass distributions. It is characterized by large-scale volcanic episodes, extreme greenhouse temperatures and mass extinctions and recoveries, including the most severe mass extinction event in Earth history at the end of the Permian (~250 Ma). Continental configuration was also markedly different from today, with most of the major landmasses coalesced into the supercontinent Pangea.

Permo-Triassic geochemical proxies and climate models have suggested that extremely high equatorial temperatures may have rendered the lower latitudes uninhabitable for complex animals, thus producing a bimodal LDG with temperate peaks. In order to test this hypothesis, we downloaded and reviewed occurrences from the Paleobiology Database across the Late Permian–Middle Triassic and used shareholder quorum subsampling (SQS) to reconstruct LDGs. These methods were used to compare the global distribution of tetrapods, both terrestrial and marine, and brachiopods and bivalves, across the end-Permian extinction and recovery interval.

Throughout the Late Permian-Middle Triassic, terrestrial tetrapods exhibited a bimodal richness distribution, with peaks in the northern low latitudes and southern mid latitudes. Marine reptiles were only found in northern mid latitudes during this interval. In contrast, brachiopods and bivalves possessed a more unimodal distribution, with their latitude of peak diversity moving northwards across the equator during the interval. These results indicate that Permo-Triassic spatial diversity patterns were shaped by a variety of factors, including extreme greenhouse climatic conditions and continental configuration.