Johannes was part of a team that published a study on the relationship between body size and mean annual temperature in PNAS. The study used both modern and fossil turtles, including from the Shungura Formation of southern Ethiopia.

Parker et al. 2022. The utility of body size as a functional trait to link the past and present in a diverse reptile clade. Proceedings of the National Academy of Sciences. https://www.pnas.org/doi/epdf/10.1073/pnas.2201948119