An armadillo is neither a reptile nor an amphibian; it is actually a mammal. Armadillos belong to the order Cingulata, which is part of a group of animals known as xenarthrans. This group also includes sloths and anteaters.
Unlike reptiles, which are cold-blooded and typically have scaly skin, armadillos have a unique shell made of bony plates covered in skin. This shell provides protection against predators. Amphibians, on the other hand, are characterized by their life cycle that includes an aquatic stage, typically as larvae, and moist skin without scales. Armadillos do not go through such a metamorphosis and have lungs for breathing air throughout their lives.
In summary, armadillos are warm-blooded mammals, equipped with a hard outer shell to defend themselves, and they exhibit characteristics that distinctly place them outside the classifications of reptiles and amphibians.