Due to their protective carapace, the armadillo once was thought to be part of the group of vertebrates associated with turtles! But in fact, these extremely ancient creatures are within one of the four basic groups of placental animals, Xenarthra, which diverged from other mammals 103 million years ago. Armadillos split within Xenarthra ~55-75 million years ago and are now classified under the order Cingulata. But what’s so special about these little insect-eating “knights in shining armor” other than its old history?
Most species of armadillo have 14-18 teeth in each jaw, but the giant armadillo has more than almost any other mammal in the world with a whopping 80-100 teeth per jaw. This is rather ironic because prior to being grouped under Xenarthra, armadillos used to be part of the now-obsolete grouping of Edentata, which means “without teeth”! Because their jaws are unable to open to large angle, they primarily use their tongues to capture their prey (mainly insects), just like the anteater. They access their buggy prey after vigorous digging with their clawed forelimbs and hindlimbs.
Many who think of the armadillo have a generalized idea in their mind: a little pig-like critter that looks like a cross between a hedgehog and a miniature anteater with a hardened shell that it can roll up into when under predation. That’s, indeed, a very accurate picture of the armadillo! Technically, though, it does not possess a shell but rather a very touch carapace that covers the upper portion of the body (shoulders, hips, middle back, tail, top of head, and lateral side of limbs).
This unique anatomical armor develops out of the skin. It is primarily made by scutes, which are like small bony shields, that is then covered by rigidly pointy skin. Underneath all that toughness, like so many creatures (metaphorically) is soft skin and hair. In order to protect themselves from injury to this more vulnerable region, most armadillos can withdraw their limbs under the hip and shoulder shields and curl up into a ball.
Thus the armadillo, a native to Florida, Georgia, South Carolina to Kansas, E. Mexico, Central and South America, and a variety of Caribbean islands, is not prey to much other than jaguars, alligators, and black bears.
Apart from males being a big larger than females, they possesses little sexual dimorphism (or different characteristic features between the sexes). But a specialty of the male armadillo is his genital pride. Yes, indeed, armadillos possess one of the largest penises in the animal kingdom. It can extend TWO-THIRDS of the entire body length of some species. To make use of his titanic gonad, the male follows the female around as a sign of “courtship”. Then after mating, embryonic development usually begins right away. Interestingly, though, some species can delay implantation of the fertilized egg by 3-4 months.
The most interesting armadillos, that which are in the genus Dasypus, are the ONLY vertebrates to exhibit obligate polyembryony, which is when one fertilized egg divides into multiple embryos so that the offspring produced are all clones of one another! Why would nature create such an anamoly? Through studies of altruism, it is thought that they will each help one another out more due to their identical genetics. Not to worry, though, they usually don’t mate with one another thereby not perpetuating a linear temporal line of clones.
The last kooky characteristic of the armadillo is its unique reaction to leprosy, an externally disfiguring bacterial disease in humans that later affects peripheral nerves the mucosa lining of the respiratory tract. Leprosy was found to infect armadillos in the wild, but unlike humans the disease shows no external symptoms until it progresses to such an extent that it actually begins to harm internal tissues. It is not known whether humans can actually contract leprosy from armadillos, but I don’t want anyone to find out…
Wacky creatures, right?