One of the most well-known, derived features of mammals is heterodonty, a difference in tooth size and/or shape along the jaw. However, some form of heterodonty is found in a wide range of other vertebrates. Interestingly, the regions of the tooth row in heterodont reptiles often mirror mammalian dental regions (i.e., incisors, canines, premolars, molars). This similarity in the organization of heterodont dentitions suggests that these dental regions are delineated by similar developmental modules in different amniote lineages.

We are using a combination of 3D geometric morphometrics and molecular development approaches to determine the role of modularity in the development of reptilian heterodont dentitions. This work may inform the origins of mammalian heterodonty as well as uncover any evidence for parallel evolution of heterodonty across vertebrates.

The evolution of the mammalian middle ear from the jaw joint of early synapsids is a classic case of the evolution of a novel, complex feature. However, the selective pressures that drove this transition are unclear because the function of the middle ear bones when they were still attached to the jaw is poorly known. I study the functional anatomy of purported hearing structures in extinct synapsids to determine whether the synapsid mandible was subjected to selection for hearing performance before the origin of mammals. We use 3D geometric morphometrics, evolutionary modeling, and comparative anatomy of extant functional analogs to answer these questions.

Some species of modern chameleons have a hearing system similar to that hypothesized to have been present in the ancestors of mammals. Instead of an ear drum, these chameleons use an expansion of their pterygoid bone to collect sound vibrations and transfer them to the inner ear. I use enhanced contrast CT scanning, gross dissection, and embryology to learn more about this unique hearing system.

Anomodonts were a highly successful clade of non-mammalian therapsids. As their name would suggest, most members of this clade had a reduced dentition, often consisting of a pair of tusks. As a result, studies of dental evolution across Synapsida often overlook this clade, despite an impressive diversity of dental features found in early anomodonts. We have used CT scanning and histology to track the evolution of features such as the periodontal ligament, tooth replacement, and multiple tooth rows in early anomodonts. This work contributes to our growing knowledge of synapsid evolution and the origin of mammalian dental features.