Skull sinuses precluded extinct crocodile relatives from cetacean-style deep diving as they transitioned from land to sea
During major evolutionary transitions, groups develop radically new body plans and radiate into new habitats. A classic example is cetaceans which evolved from terrestrial ancestors to become pelagic swimmers. In doing so, they altered their air-filled sinuses, transitioning some of these spaces to allow for fluctuations in air capacity and storage via soft tissue borders. Other tetrapods independently underwent land-to-sea transitions, but it is unclear if they similarly changed their sinuses. We use computed tomography to study sinus changes in thalattosuchian crocodylomorphs that transformed from land-bound ancestors to become the only known aquatic swimming archosaurs. We find that thalattosuchian braincase sinuses reduced over their transition, similar to cetaceans, but their snout sinuses counterintuitively expanded, distinct from cetaceans, and that both trends were underpinned by high evolutionary rates. We hypothesize that aquatic thalattosuchians were ill suited to deep diving by their snout sinuses, which seem to have remained large to help drain their unusual salt glands. Thus, although convergent in general terms, thalattosuchians and cetaceans were subject to different constraints that shaped their transitions to water. Thalattosuchians attained a stage similar to less pelagic transitional forms in the cetacean lineage (late protocetid-basilosaurid) but did not become further specialized for ocean life.
Authors
- Mark T. Young (ORCID: https://orcid.org/0000-0002-7263-6505)
- Charlotte I. W. Bowman (ORCID: https://orcid.org/0000-0002-9412-798X)
- Yanina Herrera (ORCID: https://orcid.org/0000-0002-2020-1227)
- Robert Higgins (ORCID: https://orcid.org/0000-0003-0416-1867)
- James M. Clark (ORCID: https://orcid.org/0000-0003-0980-4315)
- David Dufeau
- Rachel A. Racicot (ORCID: https://orcid.org/0000-0002-5047-8892)
- Thomas Cowgill (ORCID: https://orcid.org/0000-0002-7620-4515)
- Lawrence M. Witmer (ORCID: https://orcid.org/0000-0002-7610-0118)
- Stephen L. Brusatte (ORCID: https://orcid.org/0000-0001-7525-7319)
- Lindsay E. Zanno (ORCID: https://orcid.org/0000-0002-1654-1990)
- Julia A. Schwab (ORCID: https://orcid.org/0000-0002-6229-7116)
- Xing Xu (ORCID: https://orcid.org/0000-0002-4786-9948)
Institutions
- Museum für Naturkunde (DE)
- North Carolina Museum of Natural Sciences (US)
- National Museums Scotland (GB)
- North Carolina State University (US)
- Consejo Nacional de Investigaciones Científicas y Técnicas (AR)
- Yunnan University (CN)
- George Washington University (US)
- Chinese Academy of Sciences (CN)
- Senckenberg Research Institute and Natural History Museum Frankfurt/M (DE)
- University of Manchester (GB)
- Institute of Vertebrate Paleontology and Paleoanthropology (CN)
- Ohio University (US)
- University of Southampton (GB)
- Universidad Nacional de La Plata (AR)
- Marian University - Indiana (US)
- University of Edinburgh (GB)
Publication Details
- Journal
- Royal Society Open Science
- Published
- 2024-10-01
- DOI
- https://doi.org/10.1098/rsos.241272
- Citations
- 1
- Primary Topic
- Paleontology and Evolutionary Biology
- Type
- article
- Field-Weighted Citation Impact
- 1.59
Funders
- National Science Foundation
- Alexander von Humboldt-Stiftung
- Leverhulme Trust
- University of Southampton
- National Natural Science Foundation of China
- Consejo Nacional de Investigaciones Científicas y Técnicas
- Vetenskapsrådet
- Leibniz-Institut für Zoo- und Wildtierforschung
- Leibniz-Gemeinschaft
- Agencia Nacional de Promoción Científica y Tecnológica