Crocodiles are classified as reptiles because they possess distinct characteristics that differentiate them from amphibians. One of the main reasons is their skin. Crocodiles have tough, scaly skin that helps retain moisture and provides protection from environmental elements. This is in contrast to amphibians, which typically have moist, permeable skin that requires them to stay in wet environments.
Moreover, crocodiles have adapted to life on land and possess lungs for breathing air, whereas amphibians, like frogs, often rely on both their skin and lungs for respiration during different life stages. Crocodiles lay eggs with hard shells on land, which is another key trait of reptiles, while amphibians generally lay their eggs in water and the eggs often lack protective shells.
Additionally, crocodiles are ectothermic, meaning their body temperature is regulated by the environment around them, a common trait found in reptiles. In summary, the unique physical characteristics and reproductive strategies of crocodiles firmly place them within the reptile category, distinguishing them from amphibians.