Free shipping! Mesosaurus (meaning "middle lizard") is a significant genus of small aquatic reptiles that lived during the Early Permian period, approximately 299 to 270 million years ago. Despite the name, they are not dinosaurs. This fossil is extremely valuable because it can no longer be exported from its original habitat. The skeleton is exceptionally beautiful, and the teeth are remarkably well-preserved; it is a museum-quality fossil. Key Characteristics Appearance: They had a long, streamlined body and a powerful tail used for swimming. They typically grew to about 40–70 cm (1.3–2.3 ft) in length, though some specimens reached up to 2 meters. Skull & Teeth: They possessed elongated snouts filled with numerous very thin, needle-like teeth. These were likely used as a "strainer" to filter small crustaceans (like pygocephalomorph shrimps) from the water. Adaptations: Their nostrils were located near the eyes at the top of the snout, allowing them to breathe while remaining mostly submerged—similar to modern crocodiles. Scientific Significance: Continental Drift The Mesosaurus is most famous for providing crucial evidence for Alfred Wegener's Theory of Continental Drift: Localized Distribution: Fossils of Mesosaurus are found only in eastern South America (Brazil and Uruguay) and southern Africa. The "Impossible" Swim: As freshwater or coastal creatures, they could not have survived a journey across thousands of miles of the salty Atlantic Ocean. The Conclusion: Their presence on two distant continents proves that South America and Africa were once joined as part of the supercontinent Gondwana.