Date of Award

5-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Biology

Thesis Sponsor/Dissertation Chair/Project Chair

Robert Meredith

Committee Member

Lisa Hazard

Committee Member

Scott Kight

Committee Member

John Smallwood

Abstract

The borophagines are an extinct lineage of canids that inhabited North America for more than 20 million years. This group included genera such as Aelurodon, Borophagus, and Epicyon. Borophagines are commonly referred to as “bone-crushing dogs” because their skull morphology converged with that of extant hyenas, predators capable of consuming bone. The purpose of this study was to determine whether convergence was present in the mandible, an anatomical structure strongly correlated with feeding behavior, particularly in the genera Aelurodon and Borophagus. It was hypothesized that most borophagine taxa possessed mandibular shapes similar to those of hyenas. Numerous mandibular characters were gathered using digital calipers. Taxa examined included extant canids (canines), extant hyaenids, and multiple borophagine genera. Both bivariate and multivariate analyses were conducted to evaluate clustering patterns among taxa. Phylogenetic independent contrasts (PIC) were conducted after bivariate analysis to determine the strength of clustering patterns by removing phylogenetic effects. Bivariate analyses confirmed mandibular convergence between the borophagines and hyenas. However, multivariate analyses revealed that adaptations for durophagy occurred in different jaw regions between the two groups, suggesting parallel evolution in feeding behavior, rather than direct anatomical convergence. Additionally, Aelurodon exhibited substantial interspecific variation, with some species clustering with extant canines, suggesting ecological and functional diversity within the genus. These results indicate that further research on mandibular shape is warranted, with the incorporation of phylogenetic analyses to account for evolutionary constraints.

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