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Paleopathology in Late Triassic phytosaurs

Schädel von Mystriosuchus mit abnormaler Vertiefung (ad) im Knochen vor der Nasenöffnung (na) und möglicher Kallusbildung (pc) auf dem Rostrum. Schädellänge etwa 100 cm.

The fascinating and innovative research field of paleopathology, which focuses on the study of prehistoric diseases and injuries, helps researchers gain deeper insights into the lifestyle of long-extinct organisms. As part of a research project funded by the DFG, scientist Dr. Florian Witzmann focuses on the prehistoric diseases of phytosaurs. Phytosaurs are a diverse group of carnivorous reptiles that are particularly well suited for large-scale paleopathological studies, as thousands of specimens are preserved in museums worldwide. Despite the existence of numerous pathological specimens, there is currently no overview of the range and causes of pathologies in phytosaurs. Dr. Florian Witzmann aims to fill this knowledge gap through extensive studies of the types and frequencies of diseases in phytosaurs. His research aims to draw conclusions about the lifestyle and behaviour of phytosaurs based on the insights gained.

Phytosaurs, which are systematically assigned to the group of archosaurs, lived over 200 million years ago in the Late Triassic period. Interestingly, despite not being closely related, they can be compared to crocodiles, which are considered their modern ecological equivalent. Apart from their almost worldwide distribution at the time, little is known about phytosaurs so far. Therefore, the aim of the research project is to use paleopathology to decipher intra-species aggression patterns and trophic interactions, such as food relationships, by examining the injuries found in fossils. The following five hypotheses are at the centre of the research project:

  1. The ecological adaptations and behaviours of semi-aquatic phytosaurs resemble those of modern crocodiles, and it is likely that they exhibit similar types and frequencies of diseases.
  2. Fighting for resources and mating may have been an ancient behaviour of archosaurs, which can be observed in both crocodiles and phytosaurs from the Triassic period.
  3. In the Late Triassic, phytosaurs were the top predators in non-marine habitats and likely also fed on other predators.
  4. It can be expected that the different species of phytosaurs that lived in different paleo-habitats during their time also exhibited different types and frequencies of diseases.
  5. Like crocodiles and other reptiles, phytosaurs are ectothermic animals, which means that their bone healing after fractures resembles that of modern ectothermic animals rather than that of endothermic animals like birds and mammals. Bone healing may also have led to changes in bone structure that could have affected overall bone strength and fitness.

To test these five hypotheses, pathological specimens of phytosaurs from various museum collections in the US and Germany will be morphologically examined. Other planned methods include measurements using micro-computed tomography (µCT) and medical CT as well as bone histology. Synchrotron studies, which use particle accelerators to analyse materials, will be used to determine whether the type of bone healing indicates an overall slower or faster growth of the skeleton in phytosaurs compared to other early archosaurs and crocodiles. In addition, the 3D models of the bones from the synchrotron data will be used as a basis for finite element analysis (FEA) to obtain an overall picture of the mechanical effects of bone remodelling after injuries. By using this technique, it is possible to model physical systems and predict how they will behave under different conditions. Ultimately, the use of innovative methods will lead to the discovery of general relationships between bone healing, growth rate, and bone strength.

The results of this project will not only improve our understanding of phytosaurs, but also lead to deeper insights into the evolution of early archosaurs.