Fact of the Day : Which animals are sometimes called Hoover hogs? (from The Encyclopedia of Mammals)Armadillos
Armadillos are one of the oldest, and oddest, groups of mammals. Because of the tough protective carapace they all possess, early zoologists often linked them with shelled vertebrates such as turtles. Modern taxonomists put them in the order Cingulata.
The Xenarthra was the name given to one of the four basal groups of placental mammals, diverging from other mammals as long as 103 million years ago. Within the Xenarthra, armadillos split off into their own taxonomic branch about 55–75 million years ago. Recent molecular genetic studies suggest armadillos may be closely related to the ferroungulates, which include the carnivores, cetaceans, and artiodactyls.
Although they are now classified in the order Cingulata, armadillos were previously included in the order Xenarthra along with anteaters and sloths. Prior to the Xenarthra they were included in the now obsolete order Edentata, which means “without teeth.” This was always spurious, as they all possess rudimentary, peglike teeth that are undifferentiated (in other words, not divided into incisors, canines, or molars) and that serve to mash up their food. Most species have 14–18 teeth in each jaw, but the giant armadillo, with 80–100, has more than almost any other mammal. In the long-nosed species of the genus Dasypus, the jaws do not open very wide, so, as with the anteaters, they capture prey with their long, flexible tongues.
Though hardly lightweights, modern armadillos are puny compared with their ancestors. The largest extant species, the giant armadillo (Pri-odontes maximus), weighs 30–60kg (66–132lb), but the extinct glyptodonts were far more massive, with weights estimated at 100kg (220lb) or more. Some of these fossil forms were so large that their carapaces (up to 3m/10ft long) were used as roofs or tombs by early South American Indians.
Our knowledge of living armadillos is extremely sparse. Many species have not been studied extensively in the wild, and attempts to breed armadillos for study in captivity have been largely unsuccessful. The only well-known species currently is the nine-banded armadillo, which has been the subject of a few long-term field studies.
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