Ontogenetic variation of the Middle Triassic pseudosuchian Batrachotomus kupferzellensis: Implications for the palaeobiology of early archosaurs

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The clade of Archosauria consists of two main clades, the Ornithodira (including extant birds) and the Pseudosuchia (including extant crocodylians), and represents one of the most successful clades among tetrapods. Most of our knowledge of the palaeobiology of Mesozoic archosaurs (e.g. intraspecific variation, growth physiology and functional morphology) is based on ornithodirans (i.e. non-avian dinosaurs and pterosaurs), whereas respective knowledge is limited for early pseudosuchians, although the latter evolved a great taxonomic and ecological diversity, especially in the Triassic period. Due the availability of several specimens of different ontogenetic stages the pseudosuchian Batrachotomus kupferzellensis from the Middle Triassic outcrops of Baden Württemberg, which represents one of the terrestrial top predators during this time period, represents an appropriate object to study the palaeobiology of early pseudosuchians. Thus, the aim of the proposed project is to obtain better insights into this topic, using the Batrachotomus kupferzellensis as a model organism. Important questions to be answered during this project include the following: How long did Batrachotomus kupferzellensis take to grow to adult size and when did it reach sexual maturity? How far was its growth subject to seasonality? What does this tell us about growth rates in this taxon? Did the animal growth uniformly within different body regions? What are main ontogenetic changes in the osteology of Batrachotomus kupferzellensis? Are there changes in dentition (e.g. serration, morphology of teeth)? Do these data reveal ontogenetic differences in ecology, e.g. in terms of locomotion and feeding behaviour? If comparing the data with that of extant crocodylians, other basal pseudosuchians and basal dinosaurs, does the ontogenetic data of Batrachotomus kupferzellensis provide any evidence for heterochronic events in early archosaur evolution? What are the plesiomorphic ontogenetic and growth patterns of the hypothetical ancestor of Archosauria? The central methods to answer these questions will be the analysis of bone histology, morphometrics, detailed studies of the osteology as well as three-dimensional reconstructions of internal cranial structures based on MicroCT data. In sum, the proposed project will help to learn more about the palaeobiology of Batrachotomus kupferzellensis and closely related species, which also helps to understand their role as top-predators in the terrestrial ecosystems of the Triassic. Due to a wider comparison with other Archosauriformes, the project will obtain deeper insights in the palaeobiology of Triassic pseudosuchians and basal archosaurs in general.