You'll love my novel New Dawn, Skybison (enter shameless shilling).
Part of the backstory is the secret Vonnic Kingdoms - basically, ancient super-fucking-insane blond space elves who created the 1st Kingdom of Atlantis on flying crystal cities 65 million years ago, and were so nucking futs and good at magic they had gladiator slave fighters fight dragons and dinosaurs in massive interdimensional colosseums.
Their (half the time totally off their rockers) kings would ride Tyrannosauruses...well, before they went extinct. Then they used wyverns as mounts.
Then they disappeared because they messed with the heart of a dead god (never a good idea).