ok first of all you have to go to cold feet glacier and if you have the oonga oonga mask wear it if you find oonga oonga it will give random fossil if thats not cryo head keep digging until you find it
get someone to shoot a head to you with the fossil cannon or just keep trying at coldfeet glacier there is a corner with cryo and paki parts. it isn't at the very top, so just keep moving left and when you reach the wall, move up to the corner and search
in rivet ravine
It's fossil is at BB Base
I'l your end of days
You get an Acro in Fossil Fighters in Rivet Ravine. You have to go to tunnel # 1 but you have to have beaten the game. I think it cost's $4,000. I almost forgot the Acro head is hard to clean so get the Super Drill.
in rivet ravine,not sure what part,but somewhere there
you can get it from the mole's secret tunnel;]
you have to get 50 donation points
in the bb base lol
in the pay-to-dig site
You find it at BB Base.
It is in Rivet Ravine. I believe it is rare because I have the head fossil and it is rare. :)