Connecting the chondrocranium: Biomechanics of the suspensorium in reptiles

Title: Connecting the chondrocranium: Biomechanics of the suspensorium in reptiles

Creators: Alec T. Wilken, Kaleb C. Sellers, Ian N. Cost, Rachel E. Rozin, Kevin M. Middleton, Casey M. Holliday

Submitted February 07, 2020.
Accepted June 8, 2020.
Published online at on June 16, 2020.
Published in print Q3/2020.

DOI: 10.26049/VZ70-3-2020-02

Published by Senckenberg Gesellschaft für Naturforschung

Date (Publication Year): 2020

Resource Type (General): TEXT

Resource Type (optional): Vertebrate Zoology, Scientific Article

Description (en): Gnathostomes all share the common challenge of assembling 1st pharyngeal arch elements and associated dermal bones (suspensorium) with the neurocranium into a functioning linkage system. In many tetrapods, the otic and palatobasal articulations between suspensorium and neurocranial elements form the joints integral for cranial kinesis. Among sauropsids, the otic (quadratosquamosal) joint is a key feature in this linkage system and shows considerable variability in shape, tissue-level construction and mobility among lineages of reptiles. Here we explore the biomechanics of the suspensorium and the otic joint in five disparate species of sauropsids of different kinetic capacity (two squamates, one non-avian theropod dinosaur, and two avian species). Using 3D muscle modeling, comparisons of muscle moments, joint surface areas, cross-sectional geometries, and finite element analysis, we characterize biomechanical differences in the resultants of protractor muscles, loading of otic joints, and bending properties of pterygoid bones. For the first time, we quantify and directly compare biomechanical descriptors of pterygoid morphology and 3D muscle loads among disparate sauropsids. We propose three classes of pterygoids based on shape on biomechanical loading: brace, propulsive, and torsional. The tubular pterygoids of the lizards and birds appear to experience more diverse loading regimes than the mediolaterally narrow element of the non-avian dinosaur. Our new approaches and findings shed new light on our understanding of evolution and diversity of the suspensorium in tetrapods.

Key words: Biomechanics; Cranial Kinesis; Joints; Palates; Suspensorium

Citation: Wilken, A. T., Sellers, K. C., Cost, I. N., Rozin, R.E., Middleton, K. M., Holliday, C.M. (2020). Connecting the chondrocranium: Biomechanics of the suspensorium in reptiles.
Vertebrate Zoology, 70(3): 275-290.