- Armadillos, sloths, and anteaters (Xenarthra) are notable for the unique joints in their backbone that provide them with the strength and support they need to dig and burrow
- Armadillos, sloths, and anteaters have few or no teeth and a small brain
- Xenarthra are an ancient group of placental mammals that once roamed across Gondwanaland before the continents of the southern hemisphere separated into their present-day configuration
- When Gondwanaland divided, it split up to form South America, Africa, India, Arabia, New Zealand, and Australia, Xenarthra were initially isolated on the continent of South America but have since spread northward into areas of Central America and southern parts of North America
- Though xenarthran populations were absent from Africa, Asia, and Australia, these regions contain unrelated species that evolved to resemble xenarthrans
- Similar environmental conditions in these distant parts of the world resulted in species that, although unrelated, adapted in a similar manner and as a result resemble each other in some ways. This evolutionary dynamic is known as convergent evolution
- Examples of species that display convergent evolution with the xenarthrans include the aardvark (Africa), the pangolin (Africa and SE Asia), and the spiny anteater (Australia)
- These animals all have genetically different ancestors than the xenarthrans and consequently belong to different orders than the xenartrhans, yet they have evolved similar characteristics
- Xenarthrans were classified in the past together with the pangolin , also scaly anteater or Tenggiling, is a mammal of the order Pholidota
- There is only one extant family and one genus of pangolins, comprising eight species
- Anteaters, armadillos, and sloths are a group of eutherian mammals known as the Xenarthra
- They were once placed in the order Edentata and are still often referred to as edentates, a word that means "toothless"
- Although xenarthrans such as anteaters are indeed toothless, the giant armadillo has as many as 100 teeth, more than almost any other mammal
- Members of the mammalian group Edentata not only include the 31 living species of armadillos, true anteaters, and tree sloths, but also contain eight families of extinct ground sloths and armadillo-like animals
- Xenarthrans are a small group of insectivores and herbivores of small to medium body size (up to around 60 kg)
- In the past however, xenarthrans were much more diverse and numerous
- They radiated into about a dozen families in South America, including not only the groups known today but also animals such as the extinct giant ground sloths and giant armored gylptodonts
- Several groups of xenarthrans, mainly the ground sloths and armadillos, successfully crossed the Central American land bridge to North America when it formed during the Pliocene
- Today, only one of these species, an armadillo (Dasypus novemcinctus), still survives there; the majority of living species live in Central and South America
