What does it mean when fossils of the same species are found on different continents, such as the reptile Mesosaurus which has been found in both Africa and South America?
This is usually taken to be evidence for plate tectonic movement of the contents.
Earth's plates have been in motion for over 3 billion years. They move at a very slow rate - usually measured in millions of years - and continents are either torn apart or collide together to form very large single continents. Fossils of the same genus/species suggest that contents that were once together, must have been together in the geological past.