the largest fossil turtle seems to be the freshwater turtle "stupendemys", with an estimated total carapace length of more than 11 feet (3.3 metres). a close contender is "archelon ischyros", a sea turtle, which reached a length of 16 feet (4.8 m) across the flippers and a weight of over 4,850 lb (2,200 kg). for comparison, the largest living turtle is the leatherback sea turtle at a maximum 2000 lbs (900 kg).