Северная Двина
The first fossils were found in the Sokolki Assemblage Zone of the Kutuluk and Salarevo Formations in the Oblast of Arkhangelsk as part of the Northern Dvina River excavations led by Amalitsky during the end of the 19th century. Two nearly complete skeletons were found alongside several other skeletal remains, one of which was mounted and exhibited in Saint Petersburg in 1900 with the other following a few years later. Proper descriptions of the findings were published posthumously in 1922.