I love animals.
My too. Especially armadillos. It means little armoured one in Spanish. 
Yes they are so cute and odd looking.
Yes, they are. All species of armadillos are native to the Americas. 
Why do they have the hard shell?
More then likely because they are a decedent of an extinct group of mammals, know as glyptodants. 
When was that around?
diverged some 35 million years ago, much more recently than previously assumed.
Distribution.
Like all of the Xenarthra lineages, armadillos originated in South America. Due to the continent's former isolation, they were confined there for most of the Cenozoic. The recent formation of the Isthmus of Panama allowed a few members of the family to migrate northward into southern North America by the early Pleistocene, as part of the Great American Interchange. (Some of their much larger cingulate relatives, the pampatheres and chlamyphorid glyptodonts, made
Armadillo
Armadillos (from Spanish "little armoured one") are New World placental mammals in the order Cingulata. The Chlamyphoridae and Dasypodidae are the only surviving families in the order, which is part of the superorder Xenarthra, along with the anteaters and sloths. Nine extinct genera and 21 extant species of armadillo have been described, some of which are distinguished by the number of bands on their armour. All species are native to the Americas, where they inhabit a variety of different environments. 
Armadillos are characterized by a