Neurosensory anatomy of Varanopidae and its implications for early synapsid evolution

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dc.contributor.authorBazzana, KDen_AU
dc.contributor.authorEvans, DCen_AU
dc.contributor.authorBevitt, JJen_AU
dc.contributor.authorReisz, RRen_AU
dc.date.accessioned2025-01-13T00:44:19Zen_AU
dc.date.available2025-01-13T00:44:19Zen_AU
dc.date.issued2021-11-14en_AU
dc.date.statistics2024-09-18en_AU
dc.description.abstractVaranopids are a group of Palaeozoic terrestrial amniotes which represent one of the earliest‐diverging groups of synapsids, but their palaeoneurology has gone largely unstudied and recent analyses have challenged their traditional placement within synapsids. We utilized computed tomography (CT) to study the virtual cranial and otic endocasts of six varanopids, including representative taxa of both mycterosaurines and varanodontines. Our results show that the varanopid brain is largely plesiomorphic, being tubular in shape and showing no expansion of the cerebrum or olfactory bulbs, but is distinct in showing highly expanded floccular fossae. The housing of the varanopid bony labyrinth is also distinct, in that the labyrinth is bounded almost entirely by the supraoccipital‐opisthotic complex, with the prootic only bordering the ventral portion of the vestibule. The bony labyrinth is surprisingly well‐ossified, clearly preserving the elliptical, sub‐orthogonal canals, prominent ampullae, and the short, undifferentiated vestibule; this high degree of ossification is similar to that seen in therapsid synapsids and supports the traditional placement of varanopids within Synapsida. The enlarged anterior canal, together with the elliptical, orthogonal canals and enlarged floccular fossa, lend support for the fast head movements indicated by the inferred predatory feeding mode of varanopids. Reconstructed neurosensory anatomy indicates that varanopids may have a much lower‐frequency hearing range compared to more derived synapsids, suggesting that, despite gaining some active predatory features, varanopids retain plesiomorphic hearing capabilities. As a whole, our data reveal that the neuroanatomy of pelycosaur‐grade synapsids is far more complex than previously anticipated. © 1999-2024 John Wiley & Sons, Inc or related companies.en_AU
dc.description.sponsorshipThanks to Kevin Seymour (ROMVP) for assistance with collection numbers. Thanks to the Field Museum in Chicago for providing the raw data of Varanodon and Mycterosaurus. Thanks to the University of California Museum of Paleontology for access to the isolated braincase of Aerosaurus. Thanks to Mary Silcox and Devin Ward for assistance with bony labyrinth skeletonization and measurement protocols. This study was supported by a Natural Sciences and Engineering Research Council (NSERC) scholarship to KDB, NSERC grants to RRR and DCE, and the generous support of the Australian Nuclear Science and Technology Organisation. The authors declare that there are no competing interests.en_AU
dc.format.mediumPrint-Electronicen_AU
dc.identifier.citationBazzana, K. D., Evans, D. C., Bevitt, J. J., & Reisz, R. R. (2022). Neurosensory anatomy of Varanopidae and its implications for early synapsid evolution. Journal of Anatomy, 240(5), 833-849. doi:10.1111/joa.13593en_AU
dc.identifier.issn0021-8782en_AU
dc.identifier.issn1469-7580en_AU
dc.identifier.issue5en_AU
dc.identifier.journaltitleJournal of Anatomyen_AU
dc.identifier.pagination833-849en_AU
dc.identifier.urihttps://doi.org/10.1111/joa.13593en_AU
dc.identifier.urihttps://apo.ansto.gov.au/handle/10238/15924en_AU
dc.identifier.volume240en_AU
dc.languageEnglishen_AU
dc.language.isoenen_AU
dc.publisherWileyen_AU
dc.subjectAnatomyen_AU
dc.subjectEvolutionen_AU
dc.subjectTomographyen_AU
dc.subjectSkullen_AU
dc.subjectAnimalsen_AU
dc.subjectFossilsen_AU
dc.subjectTomographyen_AU
dc.subjectBrainen_AU
dc.subjectReptilesen_AU
dc.subjectMammalsen_AU
dc.titleNeurosensory anatomy of Varanopidae and its implications for early synapsid evolutionen_AU
dc.typeJournal Articleen_AU
dcterms.dateAccepted2021-11-04en_AU
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