Silurian era

The Silurian was an era of Earth history, prior to the great continental drift of 200,000,000 BC. After reading Dr Quinn's notes, the Third Doctor believed it was the era in which the Silurian race originated. (TV: Doctor Who and the Silurians) The Third Doctor later believed Dr Quinn got the period wrong, saying they should be from the Eocene era. (TV: The Sea Devils, PROSE: The Eight Doctors)