 Ivan III married Sophia Palaiologina, the niece of the last Byzantine emperor Constantine XI, and made the Byzantine double-headed eagle his own, and eventually Russia's, coat-of-arms.In development of the Third Rome ideas, the Grand Duke Ivan IV (the "Terrible") was officially crowned first "Tsar" ("Caesar") of Russia in 1547.The "Tsar" promulgated a new code of laws (Sudebnik of 1550), established the first Russian feudal representative body (Zemsky Sobor) and introduced local self-management into the rural regions.