Mesosaurus

Mesosaurus was an extinct aquatic reptile from the Early Permian of southern Africa and South America. Its fossils helped establish that these regions were once connected.

Permian: The geologic period from about 299 to 252 million years ago, preceding the Triassic. Mesosaurus lived during the Early Permian, before the end-Permian extinction.
Aquatic locomotion: Movement through water using body undulation, limbs, fins, or other propulsive structures. Mesosaurus's elongated body and laterally flattened tail supported swimming.
Louis Agassiz: A Swiss-American naturalist who made major contributions to paleontology, geology, and glaciology. Agassiz described Mesosaurus in the nineteenth century from Brazilian fossils.
Mesosaurus tenuidens: A species of Mesosaurus known from Early Permian fossils in South America and southern Africa. This is the best-known species and the principal source of the transcontinental fossil evidence.
Amniote: A vertebrate whose embryo develops within an amnion or related protective membranes. Mesosaurus belonged to the early amniote radiation that diversified after the Carboniferous.
Hydrodynamics: The study of fluids in motion and the forces they exert on objects. Streamlining helps explain how Mesosaurus's body shape reduced resistance in water.
Continental drift: The hypothesis that continents move across Earth's surface over geological time. Mesosaurus fossils on separated continents became evidence that Africa and South America had once been joined.
Irati Formation: A Permian geological formation in Brazil that contains fossils, including Mesosaurus remains. Its fossil beds preserve South American specimens of Mesosaurus.
Pangaea: A supercontinent that assembled most of Earth's landmasses during the late Paleozoic and early Mesozoic. Its geography explains how Mesosaurus fossils occur on both sides of the South Atlantic.
Vertebral column: The series of vertebrae that supports the body and protects the spinal cord in vertebrates. Mesosaurus's long trunk and tail vertebrae contributed to its swimming profile.

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