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Title: Palatal Biomechanics and Its Significance for Cranial Kinesis in Tyrannosaurus rex

The extinct nonavian dinosaurTyrannosaurus rex, considered one of the hardest biting animals ever, is often hypothesized to have exhibited cranial kinesis, or, mobility of cranial joints relative to the braincase. Cranial kinesis inT.rexis a biomechanical paradox in that forcefully biting tetrapods usually possess rigid skulls instead of skulls with movable joints. We tested the biomechanical performance of a tyrannosaur skull using a series of static positions mimicking possible excursions of the palate to evaluate Postural Kinetic Competency inTyrannosaurus. A functional extant phylogenetic bracket was employed using taxa, which exhibit measurable palatal excursions:Psittacus erithacus(fore–aft movement) andGekko gecko(mediolateral movement). Static finite element models ofPsittacus,Gekko, andTyrannosauruswere constructed and tested with different palatal postures using anatomically informed material properties, loaded with muscle forces derived from dissection, phylogenetic bracketing, and a sensitivity analysis of muscle architecture and tested in orthal biting simulations using element strain as a proxy for model performance. Extant species models showed lower strains in naturally occurring postures compared to alternatives. We found that fore–aft and neutral models ofTyrannosaurusexperienced lower overall strains than mediolaterally shifted models. Protractor muscles dampened palatal strains, while occipital constraints increased strains about palatocranial joints compared to jaw joint constraints. These loading behaviors suggest that even small excursions can strain elements beyond structural failure. Thus, these postural tests of kinesis, along with the robusticity of other cranial features, suggest that the skull ofTyrannosauruswas functionally akinetic. Anat Rec, 303:999–1017, 2020. © 2019 Wiley Periodicals, Inc.

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Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
The Anatomical Record
Medium: X Size: p. 999-1017
["p. 999-1017"]
Sponsoring Org:
National Science Foundation
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