Molly Ziegler

Date of Award


First Advisor

Robert Schmidt

Second Advisor

Susan Lyon


For my thesis I collected and raised Bufo americanus or American toad eggs. I preserved them at different stages to observe the skeletal ontogeny. The specimens were cleared and stained following the process written by T. Potthoff (1984). After clearing and staining I identified which stage each specimen was at based on the descriptions by Gosner (1960). The structures that appeared or changed at various stages were observed and recorded. I compared my findings to other studies on different species of frogs. Some of the studies included species that were compared with B. americanus including Spea multiplicata (Banbury and Maglia 2006), Charophrys pierotti (Wild 1999), and Ceratophrys cornuta (Wild 1997). Additionally I compared the development of the chondrocranium to a study done by Larson (2004) who looked at B. americanus. For example the hyobranchial apparatus of C. cornuta at stage 35 is strikingly similar to the hypobranchial apparatus of B. americanus. Through my study I found that there is little 5 variance in skeletal ontogeny between different species. However the order of ossification and time at which these structures ossified differed between species. The difference between my thesis and the literature that is published is that I looked at not only the chondrocranium but also the axial and appendicular skeleton. Following the development of the skeleton through the larval stages is significant because similarities between other species are noticed and this information has the potential to impact phylogenetic relationships. Other studies have only focused on the chondrocranium or the adult skeleton of frogs. This original research adds to the existing body of research focused on the skeletal ontogeny of B. americanus.