Squamates (lizards and snakes) are highly successful modern vertebrates, with over 10,000 species. Squamates have a long history, dating back to at least 240 million years ago (Ma), and showing increasing species richness in the Late Cretaceous (84 Ma) and early Paleogene (66–55 Ma). We confirm that the major expansion of dietary functional morphology happened before these diversifications, in the mid Cretaceous, 110–90 Ma. Until that time, squamates had relatively uniform tooth types, which then diversified substantially and ecomorphospace expanded to modern levels. This coincides with the Cretaceous Terrestrial Revolution, when angiosperms began to take over terrestrial ecosystems, providing new roles for plant-eating and pollinating insects, which were in turn new sources of food for herbivorous and insectivorous squamates. There was also an early Late Cretaceous (95–90 Ma) rise in jaw size disparity, driven by the diversification of marine squamates, particularly early mosasaurs. These events established modern levels of squamate feeding ecomorphology before the major steps in species diversification, confirming decoupling of diversity and disparity. In fact, squamate feeding ecomorphospace had been partially explored in the Late Jurassic and Early Cretaceous, and jaw innovation in Late Cretaceous squamates involved expansions at the extremes of morphospace.
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Data accessibility. We provide all data for the electronic supplementary material, and at the Dryad Digital Repository: doi:10.5061/dryad.f1vhhmgvw . Authors’ contributions. J.A.H-F., T.L.S. and M.J.B. designed the project. J.A.H-F. collected the data. J.A.H-F. and T.L.S. performed the analysis. All authors discussed the results, wrote the manuscript and gave final approval for publication. Competing interests. We declare we have no competing interests. Funding. This research was funded by a PhD scholarship from CONACYT, Mexico to J.A.H-F., NERC grant NE/ I027630/1 to M.J.B. and T.L.S. and ERC grant 788203 (INNOVATION) to M.J.B. and T.L.S. Acknowledgements. We thank Max Stockdale (University of Bristol) for advice on the geometric morphometric analysis and Emily Rayfield and Susan Evans for valuable discussions and their helpful suggestions. We thank Amanda Millhouse for access to the collection of the Smithsonian Institution, and the reviewers for extremely thorough and helpful comments.
© 2021 The Authors.
- Cretaceous Terrestrial Revolution