What makes it a reptile?
There are countless species and varieties of reptiles around the world. Even though there are many differences, reptiles do share a few common traits.
For starters, they use lungs to breathe. Lizards might breathe using the same muscles they use to run and crocodiles have a more flexible diaphragm, but overall, reptiles have lungs that are more advanced than amphibians, but not as refined as mammals. Reptiles also have scales made of keratin protein. Scales provide protection from predators, help retain water, and can play a role in courtship and territorial clashes. Reptiles are not the only animals to have scales, but it is a common characteristic among all reptiles.