A partial titanosaur (Sauropoda, Dinosauria) skeleton from the Maastrichtian of Nalat-Vad, Hateg Basin, Romania

摘要

Remains of titanosaurian sauropods are common in the Upper Cretaceous (Maastrichtian) of the Hateg Basin, Romania, but their usual occurrence as either isolated elements or dispersed bones in multitaxon bonebeds has hampered the understanding of their detailed anatomy or systematic position. The discovery of a partial articulated skeleton in floodplain deposits at Nalat-Vad, preserving parts of the vertebral column and pelvic girdle, allows for the first time a more detailed understanding of the axial anatomy of the Romanian titanosaurs. The specimen is described as a new taxon, Paludititan nalatzensis gen. et sp. nov., based on several autapomorphies: presence of an accessory anterior centrodiapophyseal lamina in the posterior dorsals; dorsal segments of the anterior and posterior centrodiapophyseal laminae parallel in posterior dorsals; presence of amphiplatyan mid-caudal vertebrae within the procoelous series; anterior caudal vertebrae with narrow neural spines showing anteriorly projecting anterodorsal corner, and presence of a posterolateral buttress on the iliac peduncle of the ischium. The description of Paludititan supports a higher titanosaurian diversity in the Hateg assemblage than previously recognized, and will contribute to the clarification of the taxonomic status of Magyarosaurus, the only titanosaur previously described from the area, and its included species. Phylogenetic analyses of Paludititan show it is a relatively derived titanosaur, but yields equivocal results as to its more precise systematic position and relationships, depending on the dataset used. These preliminary results suggest that development of a standard dataset for cladistic analyses should represent one of the major tasks of sauropod systematics.