Open Access

Marco Schade

• The skull is an extremely informative part of the vertebrate body. Skulls are involved to hunt, feed and drink, to nurse, fight, dig, and to many other activities. Also, main sensory organs are situated on the head in order to enable a given animal to see, smell, taste, feel, listen, equilibrate and think; hence, the head is the main connection to the external world. It follows that a skull, with and without soft tissue, can tell a lot about its owner. Each skull consists of many individual bones constituting regions (e.g., snout and braincase) that represent different aspects of an anatomical mosaic, which in turn allows deeper (palaeo)biological insights. In the past three centuries, palaeontologists dug out countless fossils from all over the world and from many preserved periods and groups, including dinosaurs. Hence, public and private collections house numerous fossil skull specimens. To further enlighten our understanding of palaeoecological, physiological and phylogenetic affinities of dinosaurian representatives belonging to different groups, and in order to reveal new aspects on their (neuro)anatomy, behaviour, ontogeny and evolution, a thoroughly examination with modern techniques is the aim of this thesis. In order to get a phylogenetically broad understanding, fossil remains from at least four extinct species, including Irritator challengeri (a theropod: mostly bipedal carnivores) from the Early Cretaceous of northeastern Brazil, Europasaurus holgeri (a sauropod: long-necked, quadrupedal herbivores) from the Late Jurassic of Lower Saxony, Emausaurus ernsti together with an unnamed taxon from the Early Jurassic of Mecklenburg-Western Pomerania, and Struthiosaurus austriacus, Late Cretaceous of eastern Austria (the latter three are thyreophorans: armoured, mostly quadrupedal herbivores), were in closer focus. To document and digitally reconstruct cranial bones and cavities therein, the material was examined with micro computed tomography (microCT). On this basis, the full morphology of the preserved anatomy was revealed, described and contextualized, for example, in conjunction with comparative anatomy and biomechanical considerations. During this process, further methods were used to investigate and depict individual fossils: macro- and microphotography, photogrammetry and phylogenetic analyses, each encompassing multiple sub-tasks and being supported by 3D prints. As part of the result, it was possible to formulate reasoned assumptions about the lifestyle of the taxa in focus. For instance, the neuroanatomy and the osteological characteristics of the spinosaurid Irritator challengeri implicate that this taxon was an agile hunter with a habitually inclined snout that was specialized in catching relatively small prey with a robust dentition and a comparably weak - but fast - bite, with a remarkable jaw mechanism which enabled the animal to kinetically widen the pharynx during lower jaw depression. The (neuro)anatomy of I. challengeri, S. austriacus, E. ernsti and E. holgeri presented here, enrich our knowledge about a plethora of (lifestyle-related) aspects of these animals, their closer relatives and the prehistoric world they lived in.