Dasypus novemcinctus, the nine-banded armadillo, is one of six extant species of Dasypus, the long-nosed armadillos (McBee and Baker, 1982). D. novemcinctus is a smallish armadillo with total lengths of 615-800 mm and weights ranging from 3-8 kg (McBee and Baker, 1982). Similar to other armadillos, the top of the head, the back and sides of the body, the tail, and the top of the legs and feet are covered with ossified dermal scutes. |
|
Armadillos belong to a group of exclusively New World mammals named Xenarthra that is characterized by having accessory vertebral articulations. Other members of this group include extant tree sloths, extant anteaters, the extinct ground sloths, and extinct glyptodonts which were closely related to armadillos. Morphological data place Xenarthra as a basally diverging branch of Placentalia, often as the sister taxon to Pholidota (Novacek, 1992a, b). An analysis of molecular data places Xenarthra in a large unnamed clade of placental mammals that includes all of the major extant groups except Afrotheria. Within this large unnamed clade, Xenarthra is the sister taxon to Boreoeutheria (all of the remaining placental groups; Murphy et al., 2001).
Dasypus novemcinctus derives its name from the presence of usually nine bands of bony armor along its body. However, the number of bands varies between eight and eleven (McBee and Baker, 1982); D. novemcinctus in North and South America typically only have eight bands (Nowak, 1991).
The nine-banded armadillo has a broad geographic range, extending from northwestern Argentina and Uruguay to the southern and midwestern United States (McBee and Baker, 1982). Dasypus novemcinctus is the only xenarthran that occurs in the wild in the United States. Its U.S. distribution includes Texas, Louisiana, Mississippi, Alabama, Florida, Georgia, South Carolina, Tennessee, Arkansas, Oklahoma, Missouri, Kansas, and Colorado (McBee and Baker, 1982). There are seven subspecies of D. novemcinctus; the one shown on this webpage is D. n. novemcinctus, the only one known to occur in the U.S. (McBee and Baker, 1982).
The fossil record indicates that Dasypus dispersed northward across the Panamanian land bridge as part of the Great American Interchange during the Pliocene. This dispersal consisted of a number of other mammalian taxa as well, including other xenarthrans. The fossil record of Dasypus in the United States extends back to the Blancan (Pleistocene). A larger extinct species, D. bellus, occupied a U.S. range similar to the modern one of D. novemcinctus (McBee and Baker, 1982; Nowak, 1991).
The skull of the nine-banded armadillo is characterized by a long, narrow rostrum. The posterior of the skull is expanded laterally, up to four times the transverse width of the snout. The lower jaw is gracile with a poorly developed symphysis and a tall, posteriorly-hooked coronoid process. Dasypus lacks canines and incisors. The postcanines are peg-like and each has a single root (McBee and Baker, 1982).
Dasypus novemcinctus is nocturnal and crepuscular in activity (McBee and Baker, 1982). D. novemcinctus is insectivorous but may also consume other invertebrates, reptiles, amphibians, some birds, and vegetable matter (Kalmbach, 1943). The nine-banded armadillo is an adept digger. Nests in its burrows are constructed from leaves, dead grass, and twigs (McBee and Baker, 1982). Armadillos are capable of swimming great distances but have also been observed walking across the bottom of shallow, narrow bodies of water (McBee and Baker, 1982).
Dasypus novemcinctus first breeds at one year of age. Ovulation occurs from June to August during which time mating takes place. However, implantation does not occur until November and young are born in either March or April (McBee and Baker, 1982).
The nine-banded armadillo usually gives birth to quadruplets, always of the same sex (Kalmbach, 1943). Sometimes deviations of two, three, or five young are born; however, there are never fewer than four embryos at the start (Kalmbach, 1943).
Armadillos are economically important because they eat harmful insects. They are a source of food in parts of the southern U.S. and in Latin America (McBee and Baker, 1982; Nowak, 1991). Armadillos are also valuable for medical research for studying multiple births, organ transplants, birth defects, and leprosy and other diseases (Nowak, 1991:533).
Literature
Kalmbach, E. R. 1943. The armadillo: its relation to agriculture and game. Game, Fish, and Oyster Commission, Austin, Texas, 61 pp.
McBee, K., and R. J. Baker. 1982. Dasypus novemcinctus. Mammalian Species 162:1-9.
Murphy, W. J., E. Eizirik, S. J. O’Brien, O. Madsen, M. Scally, C. J. Douady, E. Teeling, O. A. Ryder, M. J. Stanhope, W. W. de Jong, and M. S. Springer. 2001. Resolution of the early placental mammal radiation using Bayesian phylogenetics. Science 294:2348-2351.
Novacek, M. J. 1992a. Fossils, topologies, missing data, and the higher level phylogeny of eutherian mammals. Systematic Biology 41:58-73.
Novacek, M. J. 1992b. Mammalian phylogeny: shaking the tree. Nature 356:121-125.
Nowak, R. M. 1991. Walker’s Mammals of the World. Volume 1. Fifth edition. The Johns Hopkins University Press, Baltimore.
Talmage, R. V., and G. D. Buchanan. 1954. The armadillo (Dasypus novemcinctus). A review of its natural history, ecology, anatomy and reproductive physiology. The Rice Institute Pamphlet 41:1-135.
Links
Dasypus novemcinctus on Texas Pakrs & Wildlife.
Species account and images of Dasypus novemcinctus on the Animal Diversity Web (Univ. of Michigan Museum of Zoology).
 )
