Smith Lecture: Pia Viglietti

The Permo-Triassic mass extinction (PTME) profoundly reshaped terrestrial ecosystems, yet the mechanisms driving survival and recovery remain poorly understood. South Africa’s Karoo Basin preserves an exceptional fossil record of this transition, offering a unique opportunity to investigate vertebrate community responses to extreme environmental change. I will discuss some of the hypotheses I am currently testing about the timing and drivers of mass extinction recovery, and some preliminary results. These include some detrital zircon geochronology, which refine the traditional placement of the Permo-Triassic boundary, and support a synchronous extinction event across the basin. The paleobiological insights of the “Distaster taxon” Lystrosaurus, such as juvenile aggregation, burrowing, growth and life history patterns and broad environmental tolerance may have all been factors that contributed to its success during a prolonged biodiversity crisis. Body size analyses support a pronounced "Lilliput effect," with smaller-bodied taxa dominating Early Triassic assemblages, suggesting smaller faunivores and burrowers were robust to the effects of the extinction. Food web reconstructions indicate reduced community stability post-extinction, with true recovery delayed until the Middle Triassic. These findings provide critical insights into the origin and evolution of the dominant tetrapods of the Mesozoic (e.g., archosaurs, mammaliaforms) and today (e.g., birds, crocodilians, mammals). They also highlight the interplay of climatic stressors and biotic interactions in shaping past and present biodiversity crises.