Pokémon Ruby and Sapphire/Route 111

Use the Go-Goggles to explore the desert of Route 111. In the northeast corner of the desert is a pair of fossils. Grab one of them (the other will sink). Take it to the Devon Corp. and the researcher will determine it is a Pokémon. The Root Fossil turns into a, while the Claw Fossil turns into an.

Mirage Tower
In Pokémon Emerald, you may have found a strange tower here at times, and you probably have realized that the fossils in the place where they should be in Ruby and Sapphire are not there! Well, make sure to grab a mach bike and go into this strange tower. Get to the top, and you can finally choose the fossil you get. In Emerald, you can find the other fossil later in the game. The tower appears occasionally when entering or leaving Route 111. If you leave the tower without finding a fossil, the tower will no longer appear, but visiting the Fossil Maniac on Route 114 will trigger the tower's appearance cycle again.

Items

 * TM37 (Sandstorm): At the southern tip of the desert.