Rapid turnover of top predators in African terrestrial faunas around the Permian-Triassic mass extinction

Abstract

Catastrophic ecosystem disruption in the late Permian period resulted in the greatest loss of biodiversity in Earth's history, the Permian-Triassic mass extinction (PTME).¹ The dominant terrestrial vertebrates of the Permian (synapsids) suffered major losses at this time, leading to their replacement by reptiles in the Triassic.² The dominant late Permian predatory synapsids, gorgonopsians, were completely extirpated by the PTME. The largest African gorgonopsians, the Rubidgeinae, have traditionally been assumed to go extinct at the Permo-Triassic boundary (PTB).^3,4,5 However, this apparent persistence through the sustained extinction interval characterizing the continental PTME⁶ is at odds with ecological theory indicating that top predators have high extinction risk.⁷ Here, we report the youngest known large-bodied gorgonopsians, gigantic specimens from the PTB site of Nooitgedacht 68 in South Africa. These specimens are not rubidgeine, and instead are referable to Inostrancevia, a taxon previously thought to be a Russian endemic.⁸ Based on comprehensive review of the South African gorgonopsian record, we show that rubidgeines were early victims of ecosystem disruption preceding the PTME and were replaced as top predators by Laurasian immigrant inostranceviines. The reign of this latter group was short-lived, however; by the PTB, gorgonopsians were extinct, and a different group (therocephalians) became the largest synapsid predators, before themselves going extinct. The extinction and replacement of top predators in rapid succession at the clade level underlines the extreme degree of ecosystem instability in the latest Permian and earliest Triassic, a phenomenon that was likely global in extent.

Keywords: Permian; Synapsida; Triassic; mass extinction; paleoecology; stratigraphy.