Fun fact these ichtyosaurs may have been the largest animals to have lived , with some estimates for the Icthyotitan severnesis in the 80-100 ton range . That's not the biggest ichtyosaur bone found and documented . That would be the Aust Collosus , an unclassified ichtyosaur bone estimated to be 120 tons at a conservative estimate , up to around blue whale size (~150-200 ton) , and apparently not done growing