Date of Award

Spring 2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geology and Geophysics

First Advisor

Bhullar, Bhart-Anjan

Abstract

Within the great diversity of living vertebrates, mammals alone are distinguished by the presence of facial muscles. These delicate sheets of muscle are distributed in superficial layers of the face and neck and are responsible for critical everyday functions such as communication, feeding, and active gathering of sensory information. Despite the importance of this anatomical system in the lives of mammals, they have seldom been the focus of investigation, especially within an evolutionary context. The goal of this PhD dissertation is to explore facial muscles as a whole and integrated anatomical system with a dynamic evolutionary history and functional relevance to living organisms. Herein, I present work that employed the fossil record to identify a potential osteological correlate for the presence of facial muscles in relation to innovations in tactile sensory perception, used developmental data from embryos and neonates to understand patterns of facial muscle ontogeny, and gathered behavioral observations from social media platforms to probe the relationship between mobility performance and the complex soft tissue structures comprising the mobile nasal proboscis, one manifestation of the great morphological diversity of facial muscles. This corpus of work aspires to set a foundation for future research into facial muscles as an important innovation in mammalian evolution and their broader applications for biologically-inspired design, intersections with ecology and behavior to aid conservation efforts, and providing exciting, accessible science for public outreach.

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