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.[2] The largest freshwater turtle living today is the Arrau turtle (Podocnemis expansa), a pleurodire closely related to Stupendemys, but the Arrau turtle measures only 75 centimetres (30 in).[3]