Sibirosaurus is a nickname given to an unnamed macronarian dinosaur - a so far undescribed species and genus of sauropod.
Sibirosaurus lived in Siberia, Russia, in the Late Cretaceous some 100 million years ago in what is now known as the Kiya River. The fossil fragments were found in 2008 and reported 2015 but so far only in popular newspapers. Sibirosaurus is thus not yet a formally valid scientific name and taxonomic designation, but a temporary nickname for a taxon whose exact relationships are not known. The fossils were classified as a macronarian since they shared a few features with Brachiosaurus, titanosaurs, and other macronarians.
References
Sibirosaurus Wikipedia(Text) CC BY-SA