Here's why:
* Scales: Reptiles have scales, while mammals have fur or hair. Diamondback rattlesnakes have distinctive scales.
* Cold-blooded: Reptiles are cold-blooded, meaning they rely on external sources to regulate their body temperature. Mammals are warm-blooded and maintain a constant internal temperature.
* Lay eggs: Reptiles generally lay eggs, while mammals give birth to live young. Diamondback rattlesnakes lay eggs.