You get it by getting a life...and not playing Pokemon...
The Quick claw is located in the National Park in Pokemon Heartgold and Soulsilver.
You can not get an Armor Fossil in HeartGold.
You cannot get a Skull Fossil (Cranidos) in Pokemon HeartGold.
Anorith
If given to the Devon researcher in the Devon corporation the claw fossil can be revived into Anorith.