The family Dasypodidae, the armadillos, is the only extant family in the Order Cingulata. The Dasypodidae includes 21 species placed in 8 genera, all found only in the New World (the 21st armadillo species to be recognized, Dasypus yepesi, was described only in 1995 from the Gran Chaco of Paraguay and northern Argentina). Armadillos occur from the southern United States to the Straits of Magellan. Only the Nine-banded Armadillo (D. novemcinctus) reaches as far north as the United States.
The dorsal surface of an armadillo's body is covered with bony plates that protect the head, back, and sides and sometimes the legs and tail. Around the center of the body this armor is arranged into bands of plates separated by soft skin, allowing the animal to bend its body (the number of bands is often a useful character in distinguishing armadillo species). The back is smoothly rounded and the legs are short and powerful, with strong claws on the toes. There are three to five toes on the forefeet and five on the hindfeet. The belly is soft and naked. Most species have little or no hair, but one montane species has dense hair covering the armor.
Armadillos are generally termite and ant specialists (although other animal and even plant food is consumed as well). All species apparently sleep and raise their young in burrows they dig themselves, each species building a burrow with a characteristic size and shape. An armadillo burrow can be recognized by its smooth dome-shaped roof. The litter size is 1 to 12 young.
Head and body length among armadillo species ranges from around 125 to 1000 mm and tail length from 25 to 500 mm. The Giant Armadillo (Priodontes maximus) may weigh as much as 60 kg, whereas the little known Pink Fairy Armadillo (Chlamyphorus truncatus) and Chacoan fairy armadillo (Calyptophractus retusus), which are both thoroughly adapted to a subterranean lifestyle, weigh only around 100 g (Delsuc et al. 2012 and references therein). Armadillos have small ears. The snout, which encloses a long protrusible tongue, varies considerably in length and all species have very reduced peglike dentition, with no incisors or canines.
Armadillos generally inhabit open areas such as savannahs and pampas, but they also occur in forests (four genera and eight species are found in lowland rainforest). They travel singly, in pairs, or occasionally in small groups and may be diurnal or nocturnal. Armadillos can run surprisingly rapidly. Armadillos in a few species may roll themselves into a ball when threatened.
(Emmons 1990; Nowak 1991)
The Nine-banded Armadillo has been the focus of much research on polyembryony. Polyembryony, the production of two or more embryos from a single zygote (fertilized egg), occurs sporadically in diverse animal taxa (including humans). Among the vertebrates, only armadillos of the genus Dasypus are known to utilize polyembrony as their standard reproductive mode. Each litter is typically a set of four identical quadruplets derived from a single fertilized egg. (Prodohl et al. 1996; Loughry 1998)
In the 1970s it was discovered that Nine-banded Armadillos could contract leprosy and since then armadillos have been the primary animal model in leprosy research. Genetic and other studies have revealed that, although leprosy was absent from the New World prior to European colonization, leprosy now occurs naturally in New World armadillo populations (with a prevalence exceeding 20% in some populations). Infected armadillos have been reported in Alabama, Arkansas, Louisiana, Mississippi, Texas, and Mexico. Although the United States sees only around 150 new cases of human leprosy each year, and two thirds of these are in people who have traveled to regions with endemic leprosy, around 50 cases a year appear to have been contracted within the U.S., often in Texas or Louisiana. Truman et al. (2011) found that a high percentage of unrelated leprosy cases in the southern United States involve infection with the same unique strain of the responsible bacterium, Mycobacterium leprae, that occurs naturally among wild armadillos in the region. These armadillos thus appear to represent a large natural reservoir for M. leprae. However, high prevalence rates among armadillos have been observed in only parts of the southern United States, mainly in the western Gulf Coast states. (Truman et al. 2011 and references therein)
Nine-banded Armadillos apparently crossed the Rio Grande into southeastern Texas some time in the 1820s. In contrast, the eastern population apparently originated from a separate introduction of armadillos into south-central Florida in the 1920s, which subsequently expanded and has only relatively recently merged with the main U.S. population. The extent to which leprosy will become established in eastern armadillo populations remains to be seen. In humans, susceptibility to leprosy appears to depend on multiple genes and the majority of people appear to be naturally immune to M. leprae infection, somewhat moderating the risk to the general human population, although extensive contact with or consumption of armadillos is not recommended. (Loughry et al. 2009 and references therein; Truman et al. 2011 and references therein)
- Delsuc, F., M. Superina, M.-K. Tilak, E.J.P. Douzery, and A. Hassanin. 2012. Molecular phylogenetics unveils the ancient evolutionary origins of the enigmatic fairy armadillos. Molecular Phylogenetics and Evolution 62: 673-680.
- Emmons, L.H. 1990. Neotropical Rainforest Mammals: A Field Guide. University of Chicago Press, Chicago.
- Loughry, W.J., P.A. Prodohl,C.M. McDonough,et al. 1998. Polyembryony in armadillos. American Scientist 86(3): 274-279.
- Loughry, W.J., R.W. Truman, C.M. McDonough, M.-K. Tilak, S. Garnier, and F. Delsuc. 2009. Is leprosy spreading among Nine-banded Armadillos in the southeastern United States? Journal of Wildlife Diseases 45(1): 144-152.
- Nowak, R.M. 1991. Walker's Mammals of the World, 5th edition. Volume 1. Johns Hopkins University Press, Baltimore.
- Prodohl, P.A., W.J. Loughry, C.M. McDonough, et al. 1996. Molecular documentation of polyembryony and the micro-spatial dispersion of clonal sibships in the nine-banded armadillo, Dasypus novemcinctus. Proceedings of the Royal Society of London Series B-Biological Sciences 263(1377): 1643-1649.
- Truman, R.W., P. Singh, and R. Sharma. 2011. Probable zoonotic leprosy in the southern United States. New England Journal of Medicine 364 (17): 1626-1633.
Evolution and Systematics
Echigo moles and other digging animals break the soil surface and move as much earth as possible per stroke with short, powerful limbs and sharp claws.
"Quite different in character are the feet of the diggers, animals that habitually burrow into the earth. The friction drag of moving through the ground is potentially enormous, so the size of the limbs and the area through which they move must be kept to an absolute minimum; but at the same time, great strength is needed. The limbs of animals that lead an almost completely subterranean life, like the mole, are short and thick, and their feet are broad and powerful. Each short stroke of a foot must move as much earth as possible, and the mole's feet are spade-like with widely spaced digits. In addition, the claws of digging animals are usually large, sharp and strong, to do the work of a pickaxe in breaking the soil surface. The aardvark of South Africa (its Afrikaans name, 'earth-pig', refers to its rather pig-like head) is a curious animal that digs for food in termite's nests. Its feet are short and massive with large, almost hoof-like claws on each toe. It is said that one aardvark can dig a hole faster than six men with shovels. Not only does it dig into termite nests to eat the insects, the aardvark digs burrows 4m or more in length in which to hide during the day.
The armadillos of Central and South America are also powerful diggers, able to conceal themselves at amazing speed; they too have short, strong legs with daunting claws. The feet of the giant anteater, another excavator of ant and termite nests, are not massive as those of the aardvark. They are long and curved -- so much so that the anteater is forced to walk on the sides of its feet with an ungainly bow-legged gait. The anteater is a scratch-digger, not a maker of burrows, so its claws do not need to be as large." (Foy and Oxford Scientific Films 1982:179-180)
Learn more about this functional adaptation.
- Foy, Sally; Oxford Scientific Films. 1982. The Grand Design: Form and Colour in Animals. Lingfield, Surrey, U.K.: BLA Publishing Limited for J.M.Dent & Sons Ltd, Aldine House, London. 238 p.
Molecular Biology and Genetics
Statistics of barcoding coverage
|Specimen Records:||210||Public Records:||36|
|Specimens with Sequences:||45||Public Species:||3|
|Specimens with Barcodes:||44||Public BINs:||10|
|Species With Barcodes:||11|
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