A new macronarian sauropod from the Upper Jurassic of Portugal

The Upper Jurassic of Portugal is relatively rich in sauropod remains. We describe a new sauropod specimen, which includes a partial tail, pectoral and pelvic girdle elements, and hind limb bones, from Praia de Valmitão (Praia da Amoreira-Porto Novo Formation, upper Kimmeridgian–lowermost Tithonian). This specimen constitutes the holotype of Oceanotitan dantasi, gen. et sp. nov., which shows a unique combination of characters, including the presence of anterior caudal vertebrae with a medial accessory articulation on the prezygapophysis; a circular, rough tuberosity on the medial surface of the scapula; an elliptical concavity on the ventral face of the scapula; an ischium that is shorter than the pubis; and a robust fourth trochanter located at the midline of the posterior face of the femur. Multiple phylogenetic analyses recover Oceanotitan dantasi within Titanosauriformes, with one resolving it at the base of Somphospondyli. This taxon shares several apomorphies with some Cretaceous somphospondylans and turiasaurs, such as the transverse furrow on the chevron articulations (shared with Tangvayosaurus and Phuwiangosaurus) and the ischium being shorter than the pubis (shared with Mierasaurus and somphospondylans). Oceanotitan might represent the oldest known somphospondylan, and its establishment increases the known diversity of the Late Jurassic–earliest Early Cretaceous sauropod fauna in the Iberian Peninsula, which also consists of turiasaurs, diplodocids and macronarians (non-camarasaurid, non-titanosauriform macronarians; camarasaurids; and brachiosaurids). This high diversity in sauropods suggests that this region might have played an important role during the Late Jurassic in the dispersal and diversification of several sauropod lineages between North America, Africa, and Europe, especially macronarians.

葡萄牙上侏罗纪的蜥脚类化石资源相对丰富。本文描述了一种新的蜥脚类化石标本，该标本包括部分尾巴、胸骨和骨盆环部分以及后肢骨骼，来源于Valmitão海滩（Amoreira-Porto Novo组，上基米里阶至下提塘阶）。该标本为Oceanotitan dantasi属新种（gen. et sp. nov.）的模式标本，展现出独特的性状组合，包括前尾椎上存在中侧副关节于前椎体突；肩胛骨内侧存在圆形粗糙的突起；肩胛骨腹面存在椭圆形凹陷；坐骨短于耻骨；以及位于股骨后侧面中线的粗壮第四转子。多次系统发育分析将Oceanotitan dantasi归入泰坦龙形类，其中一次分析将其置于双凹椎形类的基础位置。该类群与某些白垩纪的双凹椎形类和土龙类具有多个衍征，例如，在椎骨关节上的横向沟（与Tangvayosaurus和Phuwiangosaurus相同）以及坐骨短于耻骨（与Mierasaurus和双凹椎形类相同）。Oceanotitan可能代表已知最古老的双凹椎形类，其确立增加了伊比利亚半岛晚侏罗纪至早白垩纪蜥脚类动物群的已知多样性，该动物群还包括土龙类、剑龙类和长颈龙类（非板龙类、非泰坦龙形类长颈龙类；板龙类；以及长颈龙类）。这种蜥脚类的高多样性表明，该地区可能在晚侏罗纪期间在北美、非洲和欧洲之间多个蜥脚类系群的扩散和多样化中发挥了重要作用，尤其是长颈龙类。