A couple things I wanna know about formations

[Raptor9468]

I have a few things I want to know about the fossil formations in general.

Are there any formations located underground entirely and are undiscovered?

Have we seen more evolved species disposited on top of another less evolved species?

Thanks for any help

[RuMert]

All the species are somehow "evolved". Ammonites could develop a keel, for example, and become more evolved though this particular adaptation happened many times with different genera. Modern nautiluses have simple eyes, which make them more evolved and fit for the environment they live in. In short, a species is more evolved when it fits better and it doesn't always mean big brains and giant claws. Yes, we see more evolved species on top of less evolved all the time

[Ludwigia]

4 hours ago, Raptor9468 said:

 Are there any formations located underground entirely and are undiscovered?

If there are any, then they haven't been discovered yet, so nobody can tell you