The earliest-known, plant-eating dinosaur was the Pisanosaurus mertii, found in the Ischigualasto formation of Argentina, South America. The dinosaur is dated at approximately 230 million years old (Late Triassic). And like its relatives Herrerasaurus ischigualastensis and Eoraptor lunensis, the Pisanosaurus was relatively small (around 3 feet [1 meter] in length), lightweight, and bipedal.