Dissertation Research: Evolution and Functional Morphology of the Theropod Foot

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As the thumb (digit I) is vital for grasping in humans, digit I (like the human big toe) in birds is critical for both their perching and holding prey. Despite the importance of digit I to birds, its anatomy, evolution, and function have not been studied. This study will address two primary questions, which will lead to a more complete understanding of the avian foot. First, the early evolution of the avian hallux will be investigated through comparisons of known avian fossils. Second, a study of foot function among living birds will compare muscle function and force output to lend insights into functional factors that may have shaped the evolution of bird feet. The evolution of the perching foot of birds appears to exemplify a relatively common phenomenon in biology, the differentiation of a structural copy. Having an "extra" copy of a structure allows the organism to explore a new functional or behavioral realm with one copy while maintaining the primitive function with another. Thus, a better understanding of avian foot evolution will contribute to understanding the evolution of other structures as diverse as the human thumb, redundant jaw musculature and fish feeding, and gene duplications, all of which are examples of this phenomenon.