Hadrocodium wui is an extinct mammaliaform that lived during the Sinemurian stage of the Early Jurassic approximately 195 million years ago in the Lufeng Formation in what is now the Yunnan province in south-western China (25.2°N 102.1°E, paleocoordinates 34.3°N 104.9°E). It is considered as the closest relative of the class Mammalia.