Stupendemys is a prehistoric genus of freshwater turtle. Its fossils have been found in northern South America, in rocks dating from the late Miocene to the very start of the Pliocene, about 6 to 5 million years ago.Stupendemys's carapace measured over 1.80 m (5.9 ft) in length and was also very wide. With an estimated total carapace length of more than 3.3 m (11 ft), it was the largest turtle that ever existed, surpassing even Archelon.