You have to beat the Elite 4 to get the other fossils. I think you can only get Old Amber until you beat the Elite 4 by breaking rocks.
This is not right. You can get any of them except the two new ones and two from either gen 1, or gen 3, depending on which version you picked.
Yes, that was right. You're not getting any fossils for anything not sixth-gen or Aerodactyl (trading aside) unless you beat the Elite 4. --- Creator of Jay's Journey (see quote!) "It's not ten years old! Therefore, it sucks!" - Nostalgia whores everywhere