Mazon Creek Fossil Fauna
Tetrapods and "Blades"
Amphibians belong to a class of egg-laying vertebrates adapted to life both on land and in water. They are the most primitive of the quadrupedal vertebrates and the first vertebrates to come ashore. Adaptations developed by adult amphibians for life on land include lungs for breathing, a tough outer skin to control water evaporation from the body and, in some species, legs. They return to the water to lay their eggs.