Morphological selectivity of the Permian-Triassic ammonoid mass extinction

Xu Dai,Haijun Song,Dieter Korn

doi:10.1130/g48788.1

Xu Dai, Haijun Song + Show 1 more

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https://doi.org/10.1130/g48788.1

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Abstract

Abstract Ammonoids suffered a diversity bottleneck during the Permian-Triassic mass extinction (PTME) and experienced a rapid diversification in the Early Triassic. However, the kinds of ammonoids that were more likely to survive the PTME and that fueled subsequent diversification are still poorly known. We compiled a comprehensive morphological data set and used the nonmetric multidimensional scaling method to reveal the impact of the PTME on the morphological selectivity of ammonoids. Our results show that postextinction taxa occupied a quite different morphospace when compared with the pre-extinction assemblages. The survivors were mainly smooth and weakly ornamented forms, while the late Permian species were dominated by coarsely ornamented forms. Contrary to previously recognized nonselective patterns, these results suggest a morphological selectivity of the Permian-Triassic crisis. Newcomers in the Griesbachian were mainly compressed and smooth forms. This morphological shift from the coarsely ornamented ammonoids dominating the Changhsingian to the smooth ammonoids dominating the Griesbachian possibly suggests an ecological turnover of ammonoids during the PTME.

Highlights

Can we predict which kinds of organisms are more likely to survive extinctions? The answer would be quite different with regard to background and mass extinctions
Some clades with specific ecological traits show higher resilience to mass extinctions than others; for example, physiologically buffered groups were less affected by the Permian-Triassic mass extinction (PTME) than unbuffered groups (Bambach et al, 2002)
The Changhsingian ammonoids are mainly concentrated on the left side, represented by coarsely ornamented species, while the Griesbachian ammonoids are mainly clustered on the right side, dominated by smooth forms

Summary

Introduction

Can we predict which kinds of organisms are more likely to survive extinctions? The answer would be quite different with regard to background and mass extinctions. Taxa with wide geographic ranges can buffer against background extinction, but not for mass extinctions (Dunhill and Wills, 2015). Mass extinctions in geological history usually act as a random nonselective pattern, affecting different clades simultaneously and globally (Payne and Finnegan, 2007). The PTME was the most severe crisis in the Phanerozoic; it killed more than 80% of marine species (Stanley, 2016; Fan et al, 2020) It coincided with large environmental and climatic upheavals; e.g., global warming and oceanic anoxia (e.g., Song et al, 2012; Sun et al, 2012). The degree of selectivity was highly variable among different clades, ecological traits, and geographic ranges

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