Modern Snake Diversity

About 66 million years ago, a massive asteroid crashed into Earth near the site of the small town of Chicxulub in what is now Mexico. The impact eradicated roughly 75% of the animal and plant species on Earth, including whole groups like non-avian dinosaurs and ammonites. New research from the Universities of Bath, Bristol, and Cambridge shows that snakes — a major group of predators comprising over 3,700 living species — started to diversify around the time of this catastrophic event.
Somewhere in Gondwanaland, a snake explores the post-extinction world of the Early Paleocene epoch. Image credit: Joschua Knüppe.
The end-Cretaceous 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 extinction event on the evolution of snakes remains poorly understood.
“Our research suggests that extinction acted as a form of ‘creative destruction’ — by wiping out old species, it allowed survivors to exploit the gaps in the ecosystem, experimenting with new lifestyles and habitats,” said senior author Dr. Nick Longrich, a researcher in the Milner Centre for Evolution at the University of Bath.
In the study, Dr. Longrich and his colleagues used fossils and analyzed genetic differences between modern snakes to reconstruct snake evolution.
Their results show that all living snakes trace back to just a handful of species that survived the Chicxulub asteroid impact 66 million years ago.
The researchers argue that the ability of snakes to shelter underground and go for long periods without food helped them survive the destructive effects of the impact.
In the aftermath, the extinction of their competitors — including Cretaceous snakes and the dinosaurs themselves — allowed snakes to move into new niches, new habitats and new continents.
Snakes then began to diversify, producing lineages like vipers, cobras, garter snakes, pythons, and boas, exploiting new habitats, and new prey.
Fossils also show a change in the shape of snake vertebrae in the aftermath, resulting from the extinction of Cretaceous lineages and the appearance of new groups, including giant sea snakes up to 10 m long.
“It’s remarkable, because not only are they surviving an extinction that wipes out so many other animals, but within a few million years they are innovating, using their habitats in new ways,” said Dr. Catherine Klein, a researcher at the Friedrich-Alexander-Universität Erlangen-Nürnberg.
“The study also suggests that snakes began to spread across the globe around this time.”
The findings are published in the journal Nature Communications.
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C.G. Klein et al. 2021. Evolution and dispersal of snakes across the Cretaceous-Paleogene mass extinction. Nat Commun 12, 5335; doi: 10.1038/s41467-021-25136-y

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