The Apatosaurus was similar to the Diplodocus, though it was shorter and more robust than its cousin. It measured 21 m long and weighed between 30 and 35 tons. At first, it was thought to be unable to support its weight and was considered amphibious. Several studies have shown that it was indeed a terrestrial animal.
It had horned pads like elephants. It was discovered in several locations in the United States. It was discovered in 1877.