How do you get omanyte on Pokemon platinum?

Answer 1

You have to have the sledge hammer and pickaxe from the the old guy in Eterna City. You dig in walls until you find a Helix Fossil. After that you have to go to the Orbeurgh City museum. You go to the guy at the end of the museum and talk to him. He will say if you want to revive the Helix Fossil into an Omantye, say yes. When he says go outside you have to go outside then back inside. After that you back to him and talk to him again. He will give you the Omantye IF you have space in your party. If you don't he says to go outside and then make space. Then when you have space enjoy your game with your Omantye!

Note: Omantye evolves into Omaster at level 40.

Hope this helped!