Armadillos are small placental mammals of the fami - Armadillos are small placental mammals of the family Dasypodidae, known for having a bony armor shell. Their average length is about 75 centimeters (30 inches), including tail. All species are native to the Americas, where they inhabit a variety of environments. In the United States, the sole resident armadillo is the Nine-banded Armadillo (Dasypus novemcinctus), which is most common in the central southern states, particularly Texas