How are fossil Pokemon obtained in BW2?

Question

I know you are given the option to choose either tirtouga or archen in Nacrene Museum. Is there a way to naturally obtain fossil(s) and/or fossil Pokemon?

Answer 1

>In Pokémon Black 2 and White 2, the former Gym Leader Lenora will give the player either Fossil when they reach Nacrene City later on in the game after defeating the Elite Four. Just like before the player must choose one of the two Fossils and then speak to the researcher standing alone at the front desk of the museum to revive it.

and

>After defeating Ghetsis, Fossils of previous generations will be given out by a Worker in Twist Mountain, with one being given out per day.

Fossil

Cover & Plume Fossils

Answer 2

There is no actual way to obtain Fossil Pokemon in the wild/naturally. The only way you can get them is by getting the corresponding fossil and reviving them. Some trainers are also shown using them. However in B/W2 you can get extra fossils by;
>After defeating Ghetsis, Fossils of previous generations will be given out by a Worker in Twist Mountain, with one being given out per day.