You find them in greenhorn plains but you have to buy all the fossil chips or beat the game and youll be able to. hope i helped!
You can find him at bonemoth
At Parchment Desert
You can find Salto fossils in the BB Base.
You can find dark fossils anywhere after completing the test in rivet ravine:)
dropping fossils are found in dark fossils anywhere around vivosaur island.
it is in the pirate ship in bottomsup bay.
In the Mole's secret tunnel after you beat the game
You find all the Cerato fossils in Rivet Ravine. NOT in the mine, in the plain.
In Rivet Ravine tunnel #5.
in rivet ravine 1st tunnel you find u-raptor fossils
Spinax is donation point vivosaur, meaning its fossils can be bought with donation points.
ANy random dig site just be lucky