Finally, the changing narrative of PTT extinctions in the Karoo emphasizes that a more nuanced approach to the end-Permian mass extinction is needed that accounts for the idiosyncrasies of the event in different geographical areas. Only by recognizing the specific details of the extinction in different places can the search for generalizations be successful.
They investigate two exposures of a slope in South Africa called the Karoo Basin – a much larger feature than the two sample outcrops they look at.
1/ Large outpourings from Siberian Trap volcanism are the likely trigger of calamitous climatic changes, including a runaway greenhouse effect and ocean acidification, which had profound consequences for life on land and in the oceans. [What? Before SUVs?]
2/ Extinction dynamics likely reflect the disappearance of theriodonts …, pareiasaurs …, cynodonts …, and dicynodont species.
3/ Our data show species-level evenness to be relatively stable throughout the Cistecephalus and Daptocephalus assemblage zones and across the main extinction acme close to the Daptocephalus–Lystrosaurus declivis Assemblage Zone boundary, likely because of the retention of some extinction acme-crossing species (Lystrosaurus curvatus, Lystrosaurus maccaigi, Moschorhinus, Promoschorhynchus) alongside the appearance of new species in the inferred recovery phase.
4/ The substantial evidence for significant climatic changes related to global warming beginning at the end of the Permian period globally likely had disastrous effects on local conditions in the Karoo. These effects were possibly related to aridity and also increased climatic variability.
5/ Nevertheless, it is very likely that fluctuating climates associated with the end-Permian mass extinction played a significant role in steadily altering the composition and structure of tetrapod communities in the uppermost DAZ, eventually causing an ecosystem collapse marked by the unstable, short-lived communities observed in the lower Lystrosaurus declivis Assemblage Zone of South Africa’s Karoo Basin.
6/ Therefore, the success of Lystrosaurus and the likely reason for its cosmopolitan distribution was not caused strictly by the ecological aftermath of the PTT or Early Triassic environments but instead had its roots in the Permian.
7/ The rise of the disaster taxon Lystrosaurus well before the Permian–Triassic boundary indicates that its success did not stem solely from an ability to survive postextinction conditions. Instead, it likely had preexisting adaptations or ecological and evolutionary versatility that allowed it to flourish under the conditions that caused widespread and sustained extinctions among other taxa.
8/ This period of instability was likely key to breaking the incumbency of previously dominant synapsid clades, paving the way for the rise of archosaurs and their relatives as a more complete recovery was achieved later in the Triassic.