From LiveScience:
Scientists have unearthed the remains of a gigantic, 200 million-year-old sea monster that may be the largest marine reptile ever discovered.
The newfound creature is a member of a group called ichthyosaurs, which were among the dominant sea predators during the Mesozoic era (251.9 million to 66 million years ago). The newly described species lived during the end of the Triassic period (251.9 million to 201.4 million years ago). Ichthyosaurs had already attained massive sizes by the early portion of the Mesozoic, but it was not until the late Triassic that the largest species emerged.