Paleopathology in Late Triassic phytosaurs as a window to early archosauriform paleoecology, behavior and bone healing

• Applicant: Dr. Florian Witzmann
• Subject Area: Geology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 459302527

Paleopathology, i.e. the study of ancient disease and injury, plays a significant role in understanding the physiology and paleoecology of long-extinct animals. Phytosaurs, a species-rich group of carnivorous archosauriforms, are well-suited for a large-scale paleopathological analysis because thousands of specimens are stored in museums in Europe and the US and – although not closely related – they can be compared with crocodylians which are often regarded as their extant ecological analogs. In spite of the large number of undescribed pathological specimens, no review of the spectrum and underlying causes of pathologies in phytosaurs exists up to date. The project has the goal to inform us about the lifestyle and behavior of phytosaurs based on a broad-based study of the types and frequencies of their skeletal pathologies. This applies especially to injuries which are indicative of an active lifestyle and are derived from trophic interactions (e.g. injuries caused by large and struggling prey), intraspecific aggression, or repetitive stress on bones and tendons. It will be assessed how type and frequency of pathologies in phytosaurs vary between different taxonomic groups, presumed trophic positions, and in the context of individual age. The nearly worldwide distribution of phytosaurs in Late Triassic continental ecosystems provides the rare opportunity to study their pathologies against the background of paleoenvironmental changes through time and between different geographical areas. The investigations will apply classic morphology, medical and micro-CT as well as histological thin sectioning. Synchrotron scanning of repair bone that was formed after injury will be carried out to assess if the kind of bone healing indicates a generally slower or faster growth rate of the skeleton in phytosaurs compared to other basal archosauriforms and in crocodylians. Furthermore, 3-D bone models derived from synchrotron scanning will be used as the basis for Finite Element Analyses (FEA) to gain an integrative picture of the mechanical consequences of the secondary bone remodeling after injuries. The comparison of phytosaur pathologies with those of extant crocodylians whose ecology and lifestyle are well known will test the hypothesis that comparable pathologies can be expected in phytosaurs and crocodylians due to an analogous lifestyle and similar morphology. The results will not only be important as independent tests of previous views on the paleobiology of phytosaurs. They will also provide a deeper insight in early archosauriform evolution and will lead to a better understanding of trophic interactions of tetrapods in Late Triassic continental ecosystems. Finally, the use of innovative methods in 3D-histology and biomechanics will allow to identify general relations between bone healing, growth rate, and the resulting consequences on the bone resistance.

• DFG Programme: Research Grants