ocr: Millennia of erosion of a sandstone outcropping in Chubut Province (above) revealed this exceptionally well preserved titanosaur skull. Found last March by paleontologist Ruben Marti- nez, it is, says Coria, "the missing piece of the puzzle" a critical source: of infor- mation on a primitive form of the plant-eaters that domi- nated southern continents during the late Cretaceous, 130 NATIONALGEOUKAPHIC, DECEMBER 1997
