The fallen one hit it perfectly. What, exactly, is so hard about checking the COMPENDIUM?
Q. At the beginning of the game, can I start with a Mysterious/Claw/Root Fossil as my Active Pokémon even if I have another "real" Pokémon on the bench?
A. Yes, you can start with a Fossil Trainer card as your Active Pokémon, at the start of the game. (Oct 2, 2003 PUI Rules Team)
Q. Can I play Old Amber as a Basic Pokemon during setup, like we do with other Fossil cards?
A. Old Amber is considered part of the fossil group in general, but not as a Fossil by name. So you may play it as a Basic Pokemon during setup, and you must play it if you have no other Basic Pokemon or other Fossil cards in your hand. (May 22, 2008 PUI Rules Team)
* Beginning with the "Diamond & Pearl" expansion, the player who goes first now draws a card at the beginning of his or her turn. That player may not play ANY Trainer cards (including Fossils), Supporter cards, nor Stadium cards from his or her hand on his or her first turn. (May 3, 2007 PUI Rules Team)