Davis, EdwardFlora, Holley2020-02-272020-02-272020-02-27https://hdl.handle.net/1794/25261The shapes of artiodactyl headgear play key roles in interactions with their environment and each other. Consequently, headgear morphology can be used to predict behavior. For example, larger, recurved horns are typical of gregarious, large-bodied animals fighting for mates. Smaller spike-like horns are more characteristic of small-bodied, paired mates from closed environments. Here, I report a genus-level cladistic analysis of the extinct family, Antilocapridae, testing prior hypotheses of evolutionary history and headgear evolution. I included 53 post-cranial, cranial, and headgear characters, expanding on previous analyses by developing 14 novel character traits. This phylogenetic analysis not only establishes ancestral headgear morphology of Antilocapridae but allows inferences of major social structure changes. These results confirm previous works inferred through comparison with artiodactyl families that antilocaprids evolved from small-bodied monogamous pairs to large-bodied gregarious herds. Our findings show multiple originations of herding social behavior.en-USAll Rights Reserved.AntilocapridaeHeadgearMorphologyPhylogenyElectronic Thesis or Dissertation