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

Dicraeosauridae（侏罗纪-白垩纪）是已知最独特的蜥脚类动物群之一。叉龙科包括来自东非、南美洲和北美洲的分类群，它们的体长大多小于10米，颈部较短，神经棘较高。叉龙科在系统分类、进化起源、地理分布、生物力学和生态学等方面的研究还很薄弱。字符编码主要局限于坦桑尼亚Tendaguru晚侏罗世的Dicraeosaurus hansemanni和阿根廷Patagonia早白垩世的Amargasaurus cazaui。D.汉斯曼尼是唯一一个拥有足够颅骨和下颌骨元素的双头龙科，可以进行3D颅骨重建。由于Dicraeosaurus属作为Dicraeosauridae的命名分类单元和第一个描述的模式的科学重要性，来自Tendaguru的保存完好且解剖学上多样的Dicraeosaurus材料将在本项目中进行彻底的重新描述和第一次ICZN符合分类修订。对Tendaguru地区叉龙属资料的修订将作为设计新的特征矩阵和首次以叉龙科为中心的系统发育分析编码的基础。系统发育分析也将包括所有其他分类群，已明确或模糊分配到叉龙科。由于Dicraeosauridae在鞭尾目的基础上的关键地位，这项工作将有助于更好地了解一般的梁龙总科的生殖发育以及这些群体内某些特征复合体的发展。D.头部的详细三维重建。hansemanni和各种二叉龙类的颈椎将提供关于颈椎空间灵活性的新信息，从而可以在所有三个维度上得出关于不同种类二叉龙类的进食范围的结论。将对Dicraeosauridae脊柱中存在的充气结构进行详细的重新评估，并将在3D中重建颈部肌肉组织和从肩带开始的颈部肌肉悬吊。所有这些信息将被整合到一个详细的生物力学研究的颈部和肩部区域的dicraeosauridesauropod。这种新的Dicraeosauridae颈部的生物力学模型将提供这些蜥脚类动物的摄食策略，它们的生态多样性和它们的摄食范围的精确信息，这是目前有争议的讨论。结合古生态和古气候资料，新的叉龙科系统发育将使详细描述叉龙科的进化历史和地理分布成为可能。

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.