Commitment to the morphological extreme – Revised systematics of the sauropod dinosaur Dicraeosaurus from the Late Jurassic of Tendaguru (Tanzania) and 3D articulation and biomechanics of the dicraeosaurid neck and shoulder girdle

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The family of Dicraeosauridae (Jurassic-Cretaceous) is one of the most peculiar known sauropod groups. Dicraeosauridae comprises taxa from East Africa, South America and North America, which are mostly less than 10 m in body length and possess rather short necks with high neural spines. Dicraeosauridae are still poorly understood in terms of their systematics, evolutionary origin and biogeography, and biomechanics including ecology. Character coding is mostly restricted to Dicraeosaurus hansemanni from the Late Jurassic of Tendaguru/Tanzania and Amargasaurus cazaui from the Early Cretaceous of Patagonia/Argentina. D. hansemanni is the only dicraeosaurid with enough cranial and mandibular elements known to allow for a 3D skull reconstruction. Because of the scientific importance of the genus Dicraeosaurus as name-bearing taxon and first described type for the family Dicraeosauridae, the well-preserved and anatomically diverse material of Dicraeosaurus from Tendaguru will undergo a thorough redescription and a first ICZN conforming taxonomic revision in this project. The revision of the material of Dicraeosaurus from Tendaguru will be taken as basis for devising a new character matrix and for coding for the first phylogenetic analysis centering on Dicraeosauridae. The phylogenetic analysis will also include all other taxa that have been unambiguously or ambiguously assigned to Dicraeosaurid. Because of the pivotal position of Dicraeosauridae at the base of Flagellicaudata, this work will contribute to a better understanding of the phylogeny of Diplodocoidea in general as well as to the development of certain character complexes within these groups. Detailed 3D reconstructions of head of D. hansemanni and the cervical vertebral column of various dicraosaurids will give new information about the spatial flexibility of the cervical vertebral column, allowing thereby conclusions about the feeding range of different species of dicraeosaurids in all three dimensions. A detailed reassessment of the pneumatic structures present in the vertebral column of Dicraeosauridae will be made and both the neck musculature and the muscular suspension of the neck from the shoulder girdle will be reconstructed in 3D. All of this information will be integrated into a detailed biomechanical study on the neck and shoulder region of dicraeosaurid sauropod. This new biomechanical model of the neck of Dicraeosauridae will provide precise information about the feeding strategy of these sauropods, their ecological diversity, and their feeding range, which is currently controversely discussed. Combined with paleoecological and paleoclimatological data, the new phylogeny of Dicraeosauridae will make a detailed characterization of the evolutionary history and biogeography of Dicraeosauridae possible.