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科（侏罗纪-白垩纪）是已知最奇特的蜥脚类动物之一。Dicraeosauridae科包括东非、南美和北美的分类群，体长大多小于10米，颈部较短，神经棘较高。双龙科在系统学、进化起源、生物地理学、包括生态学在内的生物力学等方面的认识仍然很差。字符编码主要局限于坦桑尼亚tenaguru晚侏罗世的Dicraeosaurus hansemani和阿根廷巴塔哥尼亚早白垩世的Amargasaurus cazaui。D. hansemani是唯一一种已知有足够颅骨和下颌骨的二元龙，可以进行三维颅骨重建。鉴于Dicraeosaurus属作为Dicraeosauridae科的命名分类单元和首次被描述的类型的科学重要性，本项目将对来自tenaguru的保存完好且解剖结构多样的Dicraeosaurus材料进行彻底的重新描述和第一次符合ICZN的分类修订。通过对滇达古龙资料的修订，为设计新的特征矩阵和首次以滇达古龙科为中心的系统发育分析编码奠定了基础。系统发育分析还将包括所有其他已明确或不明确地归属于双龙属的分类群。由于diraeosauridae在鞭毛纲的基础上的关键地位，这项工作将有助于更好地了解梁龙科的总体系统发育以及这些类群中某些特征复合物的发展。D. hansemani头部和各种双桡龙颈椎的详细三维重建将提供有关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不同种类双桡龙的摄食范围。将对Dicraeosauridae脊柱中存在的气动结构进行详细的重新评估，并在3D中重建颈部肌肉组织和肩部带的颈部肌肉悬吊。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的双龙类蜥脚类。这一新的双爪龙科颈部生物力学模型将为这些蜥脚类动物的摄食策略、生态多样性和摄食范围提供精确的信息，这些都是目前争论不休的问题。结合古生态学和古气候学资料，新的双剑龙科系统发育将使对双剑龙科进化历史和生物地理的详细刻画成为可能。

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.