Magnified cross section of the shaft of one of the lower leg bones of Beishanlong, revealing growth lines. According to Greg Erickson, who undertook the age analysis, "Growth line counts revealed that the animal perished during its 14th year of life. Although it is hard to fathom, this giant was still actively growing when it died. Growth line spacing in the bones of the teen-giant show only moderate decreases in width towards the periphery." Credit: G. Erickson