Reptilian anatomy is characterized by a unique skeletal structure, featuring a backbone made up of vertebrae that supports their body. They possess a skull with a strong jaw, allowing for a powerful bite. Reptiles have a three-chambered heart, except for crocodilians, which have a four-chambered heart, aiding in efficient circulation. Their skin is covered in scales made of keratin, providing protection and reducing water loss. Reptiles are ectothermic, meaning they rely on external sources for body heat. Their limbs are adapted for various modes of locomotion, with some species like snakes having evolved to move without limbs.