Amphibians are vertebrate tetrapods. Amphibia includes frogs, salamanders, and caecilians. The term amphibian loosely translates from the Greek as “dual life,” which is a reference to the metamorphosis that many frogs and salamanders undergo and their mixture of aquatic and terrestrial environments in their life cycle. Amphibians evolved during the Devonian period and were the earliest terrestrial tetrapods.

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Watch this series of five Animal Planet videos on tetrapod evolution:

  • 1: The evolution from fish to earliest tetrapod
  • 2: Fish to Earliest Tetrapod
  • 3: The discovery of coelacanth and Acanthostega fossils
  • 4: The number of fingers on “legs”
  • 5: Reconstructing the environment of early tetrapods