Since the dinosaur skeletons were found in the Patagonia region of Argentina, Mapusaurus refers to the word for “of the Earth” in the language of the Mapuche tribe of western Patagonia, and “sauros”, meaning “lizard” – hence, “earth lizard”. roseae is a combination of the rose-colored rocks where the bones were found, and the name of one of the sponsors of the excavation, Rose Letwin.