Armadillos alone possess an external bony skeleton, composed of plates of bony tissue, developed in the skin and covered with scutes of horny epidermis.
In mammals, such as dolphins and some armadillos, which have a large series of similar teeth, not always constant in number in different individuals, there may indeed be differences in the two sides; but, apart from these in describing the dentition of any mammal, it is generally sufficient to give the number and characters of the teeth of one side only.
Armadillos are omnivorous, feeding on roots, insects, worms, reptiles and carrion, and are mostly, though not universally, Peba Armadillo (Tatusia novemcincta).
Caymans, water-hogs (capinchos), several kinds of deer (Cervus paludosus the largest), ounces, opossums, armadillos, vampires, the American ostrich, the ibis, the jabiru, various species popularly called partridges, the pato real or royal duck, the Palamedea cornuta, parrots and parakeets, are among the more notable forms. Insect life is peculiarly abundant; the red stump-like ant-hills are a feature in every landscape, and bees used to be kept in all the mission villages.
The limbs are very strong, and the feet short and broad, resembling externally those of an elephant or tortois Glyptodonts constitute a family, the Glyptodontidae, whose position is next to the armadillos (Dasypodidae); the group being represented by a number of generic types.
The existence of paired caeca was previously known in a few armadillos and anteaters, but Dr Mitchell has shown that they are common in these groups, while he has also recorded their occurrence in the hyrax and the manati.
As to the Edentata, it is still a matter of uncertainty whether the pangolins (Pholidota) and the ant-bears (Tubulidentata) are rightly referred to an order typically represented by the sloths, anteaters, and armadillos of South and Central America, or whether the two first-named groups have any close relationship with one another.