Here's why:
1. Distance: The distance between Africa and South America is over 4,500 miles (7,200 kilometers). Mesosaurus would have to cross the entire Atlantic Ocean, which is one of the largest bodies of water on Earth, to travel between the two continents. This would be an enormous undertaking for such a small creature.
2. Habitat Preference: Mesosaurus was adapted to live in shallow freshwater environments, such as rivers, streams, or shallow lakes. It did not have the necessary adaptations to survive in the open ocean, such as the ability to swim long distances or withstand the high salt concentrations of seawater.
3. Geological Evidence: The geological evidence does not support the idea of Mesosaurus crossing the Atlantic Ocean. Fossils of Mesosaurus have been found in South America and Africa, but there are no known fossil records of Mesosaurus in any other parts of the world. This suggests that Mesosaurus was limited to the freshwater habitats of these two continents.
4. Continental Drift: The theory of continental drift, which proposes that the Earth's continents have moved over time, can help explain the presence of Mesosaurus fossils on both Africa and South America. It is believed that Africa and South America were once part of a larger supercontinent called Gondwana. Mesosaurus could have inhabited the freshwater environments of Gondwana, and as the supercontinent split apart, its populations became isolated on the different continents.
However, it's important to note that the exact mechanisms by which Mesosaurus came to be distributed across Africa and South America are not fully known and remain a subject of scientific debate.