The fossils are very helpful in proving the theory about the continental movement, because there's lots of different types of fossils that have been found during excavations on different continents.
To be more specific, fossils of the same species, have been found in two or more continents, that are nowadays separated, but the fossils are totally same, which will not happen if they have evolved separate from each other, thus proving that in the past, the continents were merged.