Increasing morphological disparity and decreasing optimality for jaw speed and strength during the radiation of jawed vertebrates

Science Advances, vol. 8, pp. eabl3644

Abstract

The Siluro-Devonian adaptive radiation of jawed vertebrates, which underpins almost all living vertebrate biodiversity, is characterized by the evolutionary innovation of the lower jaw. Multiple lines of evidence have suggested that the jaw evolved from a rostral gill arch, but when the jaw took on a feeding function remains unclear. We quantified the variety of form in the earliest jaws in the fossil record from which we generated a theoretical morphospace that we then tested for functional optimality. By drawing comparisons with the real jaw data and reconstructed jaw morphologies from phylogenetically inferred ancestors, our results show that the earliest jaw shapes were optimized for fast closure and stress resistance, inferring a predatory feeding function. Jaw shapes became less optimal for these functions during the later radiation of jawed vertebrates. Thus, the evolution of jaw morphology has continually explored previously unoccupied morphospace and accumulated disparity through time, laying the foundation for diverse feeding strategies and the success of jawed vertebrates.

Authors 7

1. William J. Deakin corresponding

   University of Bristol

   Affiliation as printed

   School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK

2. Philip S. L. Anderson

   University of Illinois Urbana-Champaign

   Affiliation as printed

   Department of Evolution, Ecology and Behavior, University of Illinois, Urbana-Champaign, IL, USA

3. Wendy den Boer

   Swedish Museum of Natural History

   Affiliation as printed

   Swedish Museum of Natural History, Department of Palaeobiology, Frescativägen 40, 114 18 Stockholm, Sweden

4. Thomas J. Smith

   University of Bristol

   Affiliation as printed

   School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK

5. Martin Rücklin Aachen Naturalis Biodiversity Center

   Naturalis Biodiversity Center

   Affiliation as printed

   Naturalis Biodiversity Center, Postbus 9517, 2300 RA Leiden, Netherlands

6. Philip C. J. Donoghue corresponding

   University of Bristol

   Affiliation as printed

   School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK

7. Emily J. Rayfield corresponding

   University of Bristol

   Affiliation as printed

   School of Earth Sciences, University of Bristol, Life Sciences Building, Tyndall Avenue, Bristol BS8 1TQ, UK