tetrapods
Amphibians are vertebrates that exist in two worlds. They divide their time between freshwater and terrestrial habitats. They share a number of features with air-breathing lungfish, but they also differ from lungfish in many ways. One way they differ is their appendages. Amphibians are the first true tetrapods, or vertebrates with four limbs. Modern amphibians include frogs, salamanders, and caecilians, as shown Figure below .