What fossils do you find underground on platinum?

The main thing that you do in the Sinnoh Underground is Excavating in the walls for various items. After locating them, this is controlled purely with the touch screen. It gives you a Pick Axe and a Hammer to use to try and break through the rocks in order to find 2 to 4 items.

However there is a limit on how much stress you can induce on the wall through this before the wall collapses itself. You can also find all of the fossils here after you get the National Dex; Dome Fossil, Helix Fossil, Old Amber, Claw Fossil & Root Fossil. Also you can get the Armor Fossil & Skull Fossil depending on your version at any time.

However unlike in past games, you can have any number of these fossils on you so you can go revive 20 Omanytes or Anoriths if you do so wish. The other thing you will find is the currency of the Underground; Spheres. There are 5 different kinds of Spheres found in the underground; Reds, Blues, Greens, Prisms & Pales.

However, when you keep getting them, they are not combined and there is only way to combine them and that does cause a loss in the Spheres. What you do is drop the highest amount you have on the ground and keep dropping each subsequent piece onto the ground and then pick it up.