series the centra become platycoelous, approaching the sacral vertebrae structure. The sacrum is composed by six (originally five) sacral vertebrae and they are fused into a single structure, indicating that the individual was an adult at the time of death. They are lightly more longer than the dorsals and have stocky, side to ide broadened neural spines with the top surfaces bearing small depressions. A single caudal vertebra is present after the sacral series and represents the first caudal. Its neural spine is broken and the centrum is slightly amphicoelous (concave on both ends) with sub-equal height and length. Pelvic girdle The pelvis is represented by the well-preserved left side composed by the ilium, pubis and both ischia; the right ilium and pubis were eroded though. As a whole, the pelvis is robustly built and some elements are deformed such as the left ilium, which due to taphonomical factors has been bent out of shape. Like other derived therizinosaurids, the pelvis has an opisthopubic condition where the pubis and ischium are fused and directed backwards. The ilium is stocky with an extremely well-developed and elongated preacetabular process (anterior expansion of the iliac blade), nevertheless, the postacetabular process (posterior expansion) is missing. Its pubic peduncle (a robust projection that connects to the pubis) is also well-developed, being straight and thick at the end. The acetabulum (hip socket in the middle) is large and relatively circular in shape. The pubic bone has lost its lower end and is well-fused to the ischial bone. The ischium is relatively thin, expanded, and the obturator process (a notably large projection at the end) is broken. Classification Nanshiungosaurus was in 1979 by Dong assigned to the Titanosaurinae, based on the assumption it was a sauropod genus, more specifically a titanosaurine (titanosaur). During this same year, the paleontologist Altangerel Perle described and named Segnosaurus also erecting the Segnosauridae to contain this strange taxon. After the findings of Nanshiungosaurus and Segnosaurus, more complete relatives started to be discovered, but their anatomical traits were so aberrant compared to other theropods to the point of being considered as Late Cretaceous sauropodomorph dinosaurs. In 1990, the paleontologists Rinchen Barsbold and Teresa Maryańska noted the striking similarities between the pelvises of Nanshiungosaurus and Segnosaurus, such as the ophisthopubic condition and large iliac blade. They concluded that the former was part of the Segnosauria and found this group to be a rare and