Kungurian extinctions in eupelycosaurs: a press–pulse event?

Abstract The fossil record offers a unique window into patterns of extinction and biodiversity recovery over deep time, and recent advances in analytical methods have significantly enhanced this research field. Our analysis of an updated dataset that includes 50 terminal taxa and 175 fossil occurrences of Ophiacodontidae, Edaphosauridae, and Sphenacodontidae (OES grade hereafter) using a recent implementation of the skyline fossilized birth–death model (FBD hereafter) confirms our previous conclusion that the OES grade diversified during the latter half of the Pennsylvanian but waned thereafter. However, our new results differ in several important points compared with our previous study (published in 2024). Notably, the transition between these two diversification regimes seems to have occurred earlier (at 298.9 Ma, at the Carboniferous/Permian transition), and it appears to have been marked by a moderate (0.527 survival probability), previously unreported extinction event. Also, the OES grade seems to have experienced a much more severe mass extinction event in the mid-Kungurian, with an estimated survival rate of only 0.113, which left very few surviving OES grade lineages. Climatic instability that started around the Carboniferous/Permian boundary and lasted throughout the Cisuralian, plausibly caused by intense volcanism of the Tarim Large Igneous Province and the Panjal Traps, may explain this pattern, which consists of a stagnating biodiversity followed by a brief, severe extinction event. This is reminiscent of the press–pulse model proposed by Arens and West in 2008, but if there was indeed an end-Carboniferous crisis, it could also be viewed as a new, more complex, pulse–press–pulse pattern.