As always, Pokémon X & Y offer the choice of two fossil pokémon - Tyrunt and Amaura, and as always, you'll only be able to choose one of the two.
Tyrunt is a Rock/Dragon type that comes from the Jaw fossil and will evolve into Tyrantrum. Both forms have the Strong Jaw ability which means moves such as Crunch are stronger than usual.
Amaura is a Rock/Ice type and it can be found by restoring the Sail fossil. It'll evolve into Aurorus, and both forms share the Refrigerate ability which changes normal type moves into ice type moves.