Permo-Triassic Mass Extinction

Dynamics of the recovery phase following the Permo-Triassic Mass Extinction (Jennifer Botha-Brink)

Mass extinctions s are important to macroevolution because they represent a significant decrease in biodiversity over a relatively short geological period and they can trigger a change in extinction selectivity, thus providing the opportunity for novel evolutionary paths to form. The post-extinction recovery can be as important as the extinction event itself, in terms of reshaping the long-term trajectories of organisms and allowing previously marginal groups to diversify. However identifying the selection processes during recovery intervals is difficult and remains unresolved. Understanding these processes is key to unravelling the evolutionary impact of mass extinctions. This project aims to assess the dynamics of the post-extinction ecosystems following the Permo-Triassic Mass Extinction, the most catastrophic mass extinction event in Earth’s history. I use a variety of techniques including biostratigraphy, morphology and palaeohistology to identify survival strategies, assess life history variation, and examine the origin and radiation of new or previously marginalized lineages during the recovery phase.

Community dynamics of Permo-Triassic terrestrial vertebrates from the Karoo Basin (Daryl Codron, Jennifer Botha-Brink)

The Karoo sequence of central South Africa has provided one of the most complete records of changes in terrestrial vertebrate communities before and after the extinction. Current notions suggest that terrestrial vertebrate ecosystems shifted from stable dynamics to unstable, high-risk systems from the Latest Permian to the Early Triassic. This project aims to examine changes in Permo-Triassic community composition to test the hypothesis that unbalanced foodwebs were drivers of high extinction rates in Early Triassic systems.

Ecological interactions amongst therapsid carnivores in South African Permo-Triassic foodwebs (Jacqueline Codron, Jennifer Botha-Brink)

The trophic structure of terrestrial vertebrate Permo-Triassic communities was substantially different from that of modern mammal-dominated systems. Whereas mammal communities of today typically comprise a wide diversity of herbivore relative to carnivore species, the opposite was true for therapsid and other Permo-Triassic faunas. This has led some to speculate that many Permian and Triassic vertebrate systems were imbalanced, leading to instability and relatively high rates of extinction. However, these speculations do not take into consideration the ecological effects of niche differentiation amongst carnivores. Interestingly, a similar pattern of high carnivore:herbivore diversity ratios is well-known in non-avian dinosaurs. Recent studies simulating predator-prey interactions amongst dinosaurs showed that stability could easily be achieved if carnivores partitioned the prey base by selecting for particular age or size classes within herbivore taxa. Our research combines stable isotope, morphological, and histological tools to investigate patterns of dietary niche partitioning amongst Permo-Triassic carnivores, and ultimately to test hypotheses about ecological stability in those systems.

Taphonomy of Early Triassic vertebrates from the Karoo Basin (Jennifer Botha-Brink, in collaboration with Roger Smith, Iziko Museums of South Africa)

This project is a taphonomic study of the vertebrates that lived during the Early Triassic. Currently, there are two opposing hypotheses relating to the environment during the Early Triassic. One theory maintains that the climate after the Permo-Triassic Mass Extinction became hot, arid and highly seasonal with monsoon-type rainfall. In contrast, another theory states that the post-extinction climate became hot and wet, with excessive rainfall resulting in a greenhouse type of environment. We agree with the first theory and the objectives of this project are to find evidence of drought in the Karoo Basin by documenting the taphonomy of vertebrates from the Lower Triassic. The project involves the documentation of the mode of burial, the degree of articulation or fragmentation, the death pose and if it died on the surface or within a burrow. This gives us information on the conditions during fossilization, which in turn reveals important information on the environment at the time.