Is an armadillo a marsupial mammal?

No, an armadillo is not a marsupial mammal. Armadillos belong to the order Cingulata, which is part of the superorder Xenarthra. They are not closely related to marsupials, which belong to the order Marsupialia. Marsupials are characterized by having a pouch where they carry their young, while armadillos have a bony shell that protects them.