The fact that similar fossils are found on both sides of the ocean is evidence for continental drift, which is the idea that the continents have moved over time.

Here's why:

* Fossil distribution: The presence of identical or very similar fossils on continents now separated by vast oceans suggests that these landmasses were once connected. It's unlikely that the same species could have evolved independently on separate continents.

* Matching geological formations: Not only fossils, but also matching geological formations on different continents support the idea of a once unified landmass.

* Puzzle-like fit: The shapes of continents, particularly South America and Africa, fit together like pieces of a puzzle, further hinting at a past connection.

The discovery of these similarities was crucial in the development of the theory of plate tectonics, which explains the movement of Earth's continents over millions of years.