There are 21 species of armadillo, according to the Integrated Taxonomic Information System (ITIS). Some armadillos are very small, while others are huge. The smallest is the pink fairy armadillo, which is about 6 inches (15 centimeters) long. Giant armadillos are the largest species, and are about 5 feet (1.5 meters) long, according to National Geographic.

An armadillo's armor is made up of overlapping plates covering the back, head, legs and tail. The number of armored bands identifies the different species, according to the San Diego Zoo. Only one species, the three-banded armadillo, can roll itself into a hard armored ball to defend itself against predators. Other armadillo species simply dig a hole quickly and hunker down so that their tender stomach is protected and their armor is the only thing visible.

Armadillos have pointy snouts and long, sticky tongues, similar to anteaters, which are close cousins. Their eyesight is poor, so they hunt with a highly developed sense of smell. They also have wiry hairs along their sides and belly, which they use to feel their way around, like curb feelers on some cars. They also have strong legs and sharp claws for digging.