(Georgia Institute of Technology, 2022-05)
Shinn, Ollie
Toad ears are usually composed of a tympanic membrane, tympanic annulus, columella, and inner ear, and vary greatly across species. In order to investigate the state and evolutionary history of ears within the toad family Incilius, I compiled information on the tympanum and columella presence and shape from first hand CT scans and observations as well as previously documented descriptions. I applied this information to the phylogeny presented by Mendelson et al (2011) and reviewed them for changes throughout evolutionary history. I concluded that the common ancestor of Incilius had both a tympanum and a columella, and both had been lost and regained at least once in evolutionary history, most likely around the same point in evolution. Based on those conclusions, I predicted the most likely state of columella for species I did not have data on. While hearing is important for many toads’ social behaviors, it is important to recognize that several studies have shown that amphibians without complete ears can still perceive sounds.