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

古病理学，即对古代疾病和损伤的研究，对于理解灭绝已久的动物的生理学和古生态学具有重要作用。植龙是一类物种丰富的食肉始祖龙，非常适合进行大规模的古病理学分析，因为数以千计的标本储存在欧洲和美国的博物馆里，尽管它们没有密切的亲缘关系，但可以与鳄鱼进行比较，鳄鱼通常被认为是它们现存的生态类似物。尽管有大量的未描述的病理标本，但到目前为止，还没有关于植龙的光谱和潜在的病理原因的综述。该项目的目标是在对植龙骨骼病理类型和频率进行广泛研究的基础上，向我们提供有关植龙的生活方式和行为的信息。这尤其适用于表明积极生活方式的伤害，这些伤害源于营养相互作用(例如，大型和挣扎的猎物造成的伤害)、种内攻击或对骨骼和肌腱的反复压力。将评估植龙的病理类型和频率如何在不同的分类群、推定的营养位置和个体年龄的背景下发生变化。植物龙在晚三叠世大陆生态系统中的分布几乎遍及全球，这为在不同地理区域和时间内古环境变化的背景下研究植物龙的病理提供了难得的机会。这些研究将应用经典的形态学、医学和显微CT以及组织学切片。将对受伤后形成的修复骨进行同步辐射扫描，以评估骨骼愈合的类型是否表明植龙骨骼的生长速度通常比其他基础始龙和鳄鱼的骨骼生长速度更慢或更快。此外，来自同步辐射扫描的3-D骨模型将被用作有限元分析(FEA)的基础，以获得损伤后继发性骨重建的力学后果的综合图像。将植龙的病理学与已知生态和生活方式的现存鳄鱼的病理学进行比较，将检验这样一种假设，即由于相似的生活方式和相似的形态，植龙和鳄鱼可以预期会有类似的病理学。这一结果不仅将是对之前关于植物龙古生物学观点的独立检验，而且将是重要的。它们还将提供对早期始龙进化的更深层次的洞察，并将有助于更好地理解晚三叠世大陆生态系统中四足动物的营养相互作用。最后，3D组织学和生物力学中创新方法的使用将使我们能够确定骨愈合、生长速度和由此对骨阻力产生的后果之间的一般关系。

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.