The exact point in earth's history that the Silurians belong to is unclear. Both the actual Silurian period and the Eocene epoch of the Tertiary period have been proved incorrect.
The most likely period for their evolution is the late Cretaceous period, and having been culturally and technologically developed enough, they would have survived the asteroid impact that wiped out the dinosaurs, and went into hibernation during the early Eocene, when the first primates evolved (when awakened, they show an awareness of "apes"). Of course, this is purely speculative.
The Silurians are a fictional species that were created for the BBC television show Doctor Who
"You give us space, we can bring new sources of energy, new methods of water supply, new medecines, scientific advances. We were a great civilisation; you provide a place for us on the surface, we'll give you knowledge and technology beyond humanity's dreams. We work together, this planet could achieve greatness!" - Eldane, ambassador of the Cwmtaff Silurian Tribe
"We will wipe the vermin from the surface and reclaim our planet" - Allayah, Silurian Warrior