LAUSR

Abstract Sibirotitan astrosacralis nov. gen., nov. sp., is described based on isolated but possibly associated cervical and dorsal vertebrae, sacrum, and previously published pedal elements from the Lower Cretaceous (Barremian?) Ilek Formation at Shestakovo 1 locality (Kemerovo Province, Western Siberia, Russia). Some isolated sauropod teeth from the Shestakovo 1 locality are referred to the same taxon. The phylogenetic parsimony analyses place Sibirotitan astrosacralis nov. gen., nov. sp., as a non-titanosaurian somphospondyl titanosauriform. The new taxon exhibits four titanosauriform and one somphospondylan synapomorphies, and one autapomorphy – a hyposphene ridge that extends between the neural canal and the postzygapophyses. It differs from all other Somphospondyli by having only five sacral vertebrae. The new taxon shares with Euhelopus and Epachtosaurus sacral ribs that converge towards the middle of the sacrum in dorsal view. Sibirotitan astrosacralis nov. gen., nov. sp., is only the second sauropod taxon from Russia and one of the oldest titanosauriform described so far in Asia.