as Tengrisaurus (from the Barremian or Aptian of Russia) and Jiangshanosaurus (from the Albian of China). The latter was noted to have similar dorsal vertebrae to the much older Sibirotitan. Most of the referred specimens, although dis-articulated, are thought to have belonged to a single individual; it was suggested the large remains found in the 1960s could have originally been from the same skeleton as later remains, some found as recently as 2011. A singular cervical centrum was noted to be juvenile, and from a different individual, as the rest of the remains belonged to an adult animal. Among these fossils, PM TGU 120/10-Sh1-22, a dorsal vertebra, was selected as the holotype specimen. An axis vertebra from the type locality was later assigned to Sibirotitan astrosacralis as well. Description Two characters were found to distinguish it from its close relatives. The hyposphene ridge on its dorsal vertebrae was particularly high, unlike other members of Titanosauriformes; this is the only autapomorphy of the taxon. Its possession of only five sacral vertebrae distinguishes it from all other somphospondyls, as possession of six is a synapomorphy of the clade. It was noted that juveniles have fewer vertebrae, but given the adult age of the individual examined, the trait was instead seen as an evolutionary reversal. Using one of the cervical vertebrae, a size estimate was attempted. They found it roughly corresponded in size to that of the diplodocoid sauropod Apatosaurus, and suggested a similar size of 20 tonnes might have been possible. Classification Several characters were noted among the remains, four of which allowed classification in the group Titanosauriformes. These include the fashion in which the tooth crowns align in the jaw, presacral bone texture, and both the elongation of and the concave nature of certain parts of the cervical centra. An additional character, relating to the size of the arch of the cervical vertebrae, was used to assign it more specifically as a member of Somphospondyli. Characters in its vertebrae and ribs were found shared with Epachtosaurus and Euhelopus. A phylogenetic analysis was performed. It was noted that many differing and conflicting matrices exist for analyzing the systematics of Titanosauriformes, due to many taxa being poorly known. Because it is suited well for basal Titanosauriformes in particular, the matrix of Mannion et al. (2013) was chosen. In this analysis, it was found to be a relatively advanced non-titanosaurian somphosondyl. The following phylogenetic