The Sea Devils and the Silurians lived in the time of the dinosaurs until the catastrophe of the Moon's approach drove them into hibernation. They slept longer than planned and emerged late in the 20th century. The human scientist who discovered the Silurians estimated their era incorrectly. A later "Doctor Who" story said that they should have been classified as the Eocenes. A second species of hibernating Earth reptiles lived primarily underwater. They were labeled "sea devils" by a frightened, superstitious construction worker who encountered them.