Evolution and dispersal of snakes across the Cretaceous-Paleogene mass extinction

Catherine G Klein,Matthew A Wills,Davide Pisani,Rebecca Lakin,Daniel J Field,Nicholas R Longrich

doi:10.1038/s41467-021-25136-y

Abstract

Mass extinctions have repeatedly shaped global biodiversity. The Cretaceous-Paleogene (K-Pg) mass extinction caused the demise of numerous vertebrate groups, and its aftermath saw the rapid diversification of surviving mammals, birds, frogs, and teleost fishes. However, the effects of the K-Pg extinction on the evolution of snakes—a major clade of predators comprising over 3,700 living species—remains poorly understood. Here, we combine an extensive molecular dataset with phylogenetically and stratigraphically constrained fossil calibrations to infer an evolutionary timescale for Serpentes. We reveal a potential diversification among crown snakes associated with the K-Pg mass extinction, led by the successful colonisation of Asia by the major extant clade Afrophidia. Vertebral morphometrics suggest increasing morphological specialisation among marine snakes through the Paleogene. The dispersal patterns of snakes following the K-Pg underscore the importance of this mass extinction event in shaping Earth’s extant vertebrate faunas.

Highlights

Mass extinctions have repeatedly shaped global biodiversity
We explore the effect of the K-Pg extinction event on vertebral morphological disparity, in order to directly incorporate an extensive sample of fossil taxa, while benefiting from the tendency for morphological disparity indices to be less sensitive to sampling biases than diversity estimates[39]
Implementing alternative assumptions regarding the quality of the fossil record by manipulating parameterizations of priors on fossil calibrations influenced mean estimated ages, but confidence intervals for nodes of interest—in particular for crown Afrophidia—converged near the K-Pg boundary

Summary

Introduction

Mass extinctions have repeatedly shaped global biodiversity. The Cretaceous-Paleogene (K-Pg) mass extinction caused the demise of numerous vertebrate groups, and its aftermath saw the rapid diversification of surviving mammals, birds, frogs, and teleost fishes. Most studies[31,32,33,34] suggest that the majority of extant snake clades diverged in the Cretaceous, several analyses hint at a more recent diversification of the major subclade Alethinophidia[30,35,36]. Given this uncertainty, we attempted to improve our understanding of the timescale of crown snake diversification and the methodological factors that affect these inferences. We find a pattern of increasing vertebral disparity in the aftermath of the extinction, with concurrent increases in average and maximum body size, and dispersal to previously unoccupied landmasses

Methods

Results

Conclusion