Silurians (and their water-dwelling cousins, the Sea Devils)
ELEVENTH DOCTOR: These must be the only ones awake; the others must still be in hibernation.
NASREEN: So why did they go into hibernation in the first place?
ELEVENTH DOCTOR: Their astronomers predicted a planet heading to Earth on a crash course. They a built life underground and put themselves to sleep for millennia in order to avert what they thought was the apocalypse. When in reality, it was the moon, coming into alignment with the Earth.
MALOKEH: How can you know that?
ELEVENTH DOCTOR: Long time ago, I met another tribe of homo reptilia — similar, but not identical.
RESTAC: Others of our species have survived?
ELEVENTH DOCTOR: The humans attacked them. They died. I’m sorry.
— Cold Blood