Author ORCID Identifier:
Date of Graduation
5-2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Anthropology (PhD)
Degree Level
Graduate
Department
Anthropology
Advisor/Mentor
Terhune, Claire
Committee Member
Ross, Callum
Second Committee Member
Plavcan, Jospeh
Third Committee Member
Delezene, Lucas
Keywords
Covariation; Geometric Morphometrics; Hyoid Apparatus; Ontogeny; Primate Anatomy
Abstract
The hyoid is central to many important functions such as feeding, vocalization, and breathing. However, primate hyoid morphology has been widely understudied compared to other aspects of craniofacial morphology. This dissertation aimed to bridge gaps in the current understanding of primate hyoid morphological variation and the hyoid’s relationship with mandibular morphology. Using microCT, diceCT, and three-dimensional geometric morphometric methods, this work details broad taxonomic variation of basihyal shape, resting hyoid position, and suprahyoid muscle architecture in primates, and assesses such variation for the effects of phylogeny, allometry, and covariation between these elements and mandibular shape. These analyses were also conducted using an ontogenetic approach within and between two closely related species with well-documented dietary differences. Results from the broad taxonomic analyses revealed distinct basihyal morphologies between anthropoid and non-anthropoid primates, likely reflecting differing adaptations to chewing or swallowing. Both basihyal shape and hyoid position exhibit significant relationships with both hyoid centroid size and mandible length, indicating that size plays an important role in hyoid morphology. More critically, this work is the first to quantitatively demonstrate that the morphologies of the hyoid and mandible significantly covary, suggesting that these two bony elements are integrated with each other during feeding. Analyses of the suprahyoid muscles across primates suggest similar scaling patterns as those found in the masticatory apparatus, where muscle mass scales with positive allometry, while fiber length scales more negatively, resulting in isometric scaling of suprahyoid physiological cross-sectional area. Additionally, this work reveals interesting relationships between suprahyoid muscle architecture and basihyal shape. Finally, ontogenetic analyses in capuchins revealed that Sapajus possess overall larger basihyals and more robust suprahyoid muscles than Cebus and that these differences were present in the earliest age stages. Interestingly, only Cebus exhibited significant hyomandibular covariation, while Sapajus did not. Such findings show that covariation between the mandible and hyoid differ even in closely related taxa. Overall, this dissertation shows that hyoid morphology is complex due to its relationships with phylogeny, size, biomechanical coordination, and development.
Citation
Taylor, P. M. (2026). An Assessment of the Basihyal and its Functional and Ontogenetic Relationships to the Masticatory Apparatus in Primates. Graduate Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/6102
