Mesosaurus is an extinct genus of anapsid reptile from the Permian period. It was about 1 m (3 ft 4 in) long.

The return to the water

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Mesosaurus was one of the first reptiles to return to the water where its amphibian ancestors originally came from. Its feet were webbed, it was streamlined and its long tail sported a high fin. Since the hind legs were much longer they are presumed to have been used to propell the creature through the water. Its body was flexible and could easily move sideways, but it could not turn as a result of highly thickened ribs- a feature also seen in modern sea cows.

Skull and teeth

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Mesosaurus had a small skull with long jaws. The nostrils were located at the top, allowing the creature to breathe with only the upper side of its head breaking the surface (similar to a crocodile). Mesosaurus's most striking feature were its numerous, thin teeth. Each teeth had its own socket, which is a carnivore trait, but they were too thin to catch prey with. Instead, they are thought to have been used to filter plankton from the water.

Distribution

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Mesosaurus was significant in the proving of the theory of continental drift because its remains were found in southern Africa and eastern South America- two far-spaced areas. Because Mesosaurus lived in fresh water and therefore could not have crossed the Atlantic Ocean, this distribution indicated that Africa and South America used to be joined together. Indeed, all the world's continents were joined into one supercontinent called Pangaea in the time Mesosaurus existed.