Delayed recovery of non-marine tetrapods after the end-Permian mass extinction tracks global carbon cycle

Abstract

During the end-Permian mass extinction, marine ecosystems suffered a major drop in diversity, which was maintained throughout the Early Triassic until delayed recovery during the Middle Triassic. This depressed diversity in the Early Triassic correlates with multiple major perturbations to the global carbon cycle, interpreted as either intrinsic ecosystem or external palaeoenvironmental effects. In contrast, the terrestrial record of extinction and recovery is less clear; the effects and magnitude of the end-Permian extinction on non-marine vertebrates are particularly controversial. We use specimen-level data from southern Africa and Russia to investigate the palaeodiversity dynamics of non-marine tetrapods across the Permo-Triassic boundary by analysing sample-standardized generic richness, evenness and relative abundance. In addition, we investigate the potential effects of sampling, geological and taxonomic biases on these data. Our analyses demonstrate that non-marine tetrapods were severely affected by the end-Permian mass extinction, and that these assemblages did not begin to recover until the Middle Triassic. These data are congruent with those from land plants and marine invertebrates. Furthermore, they are consistent with the idea that unstable low-diversity post-extinction ecosystems were subject to boom–bust cycles, reflected in multiple Early Triassic perturbations of the carbon cycle.

Provincialization of terrestrial faunas following the end-Permian mass extinction

“…First, as previously shown for tetrapods (3,4,12,17) the taxonomic composition of assemblages preserved in each basin underwent wholesale revision; there are no species (or genera) found in both Upper Permian and Middle Triassic rocks. Among basins, a second, largerscale transition also occurred.…”

“…The end-Permian event had a devastating effect on global biodiversity, with estimates of over 90% species extinction among marine invertebrates and over 70% in terrestrial animals (but significantly less among plants) (3)(4)(5)(6)(7)(26)(27)(28). Recent work has suggested that recovery was delayed because of prolonged environmental disturbance, manifested by wide fluctuations in the global carbon cycle that persisted for most of the Early Triassic (13,29), and that substantial ecosystem diversity was not regained until about 8-million-years later in the Middle Triassic (12,13,30,31). On land, the recovery of terrestrial vertebrates has been studied extensively in the Karoo Basin of South Africa.…”

“…As a result, patterns documented in the Karoo Basin have necessarily been considered representative of the southern hemisphere as a whole (5,12,24). Our work has shown that the four basins preserving Upper Permian fossils (Malawi, South Africa, Tanzania, Zambia) were, despite markedly different basin architecture and fill, characterized by a single, highly interconnected community during the Permian.…”

“…These two zones are sufficiently separated from the end-Permian mass extinction to represent reasonable glimpses of pre-and postextinction assemblages. Indeed, the Cynognathus AZ is considered the first postextinction biozone to feature a stable global carbon cycle (12,13). In addition to the Karoo, we collected data on the composition of tetrapod faunas in four other areas preserving fossiliferous Upper Permian and Middle Triassic beds, namely the (i) Luangwa Basin of Zambia, (ii) Ruhuhu Basin of Tanzania, (iii) Chiweta beds of Malawi, and (iv) Beacon Basin of Antarctica (see Fig.…”

Dinosaur morphological diversity and the end-Cretaceous extinction

“…Unfortunately, records of dinosaur disparity across the entire Mesozoic are not yet available for comparison, and are difficult to compile because of low sample sizes in many stage-level intervals, but the establishment of these patterns should be a major goal of research on dinosaur biodiversity. Furthermore, there are known instances in the fossil record in which major vertebrate clades endured catastrophic diversity and disparity losses, both during mass extinctions and normal background times, but later rebounded [36][37][38][39][40] . A satisfactory understanding of the causes and tempo of the non-avian dinosaur extinction remains difficult, but the compilation of additional biodiversity metrics (such as disparity) and increased study of non-North American taxa is helping to bring clarity.…”