Answer: Because the same Fossils were found on other continents.
Explanation:
The world used to be connected but then what I call the Continental Drift started and the world broke apart, along with the dinosaurs splitting in two or more packs.
(125 mg Na) x (1 g/1000mg) x (1 mol of Na/22.99 g) = 5.43 E -3 mols of Na
5.43 E -3 mols x 6.022 E 23 = 3.27 E 21 Na atoms