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| 14.31 | Level V life: (placental/land) anteaters, sloths | |
| An anteater or sloth is any member of the mammalian order Edentata, which includes 31 living species distributed among the armadillos , true anteaters, and tree sloths, as well as eight extinct families of ground sloths and armadillo-like animals. The living families and six of the extinct families constitute the suborder Xenarthra. A second suborder, Palaeanodonta, consists of two extinct families. The entire evolutionary history of the edentates is restricted to the Western Hemisphere, and the majority of the living species occur today in South America. | ||
| Edentata means lacking teeth, though in reality only the true anteaters are toothless. The majority of edentates have simple, peglike cheek teeth that lack enamel; canine-like teeth do occur in some forms. Certain armadillos may have as many as 100 teeth. Edentates possess specialized traits, such as reduced dentition, a long sticky tongue, powerful, clawed, forefeet, associated with their insect diets. They also have primitive traits, such as the possession of five toes on the hindfeet, a simple uterus, and small, uncomplicated brain, which place them close to the primitive stock that gave rise to the infraclass Eutheria, which includes all placental mammals. | ||
| Living edentates range in size from the tiny pink fairy armadillo or "lesser pichiciego" (Chlamyphorus truncatus) of Argentina, measuring about 16 centimetres (6.3 inches) in length and weighing little more than 100 grams (3.5 ounces), and the slightly larger two-toed or silky anteater (Cyclopes didactylus), just over 37 centimetres (14.6 inches) long and weighing about 325 grams (11.5 ounces), to the 60-kilogram (132-pound) giant armadillo (Priodontes giganteus), nearly 1.5 metres (five feet) long, and the giant anteater (Myrmecophaga tridactyla), which weighs up to 25 kilograms (55 pounds) and may be over two metres (6.6 feet) in length. Among extinct forms, an Oligocene armadillo, Prozaedyus proximus, had a skull under eight centimetres (3.1 inches) in length and was only somewhat larger than the smallest of the living armadillos. The Pleistocene ground sloth, Megatherium americanum, was six metres (20 feet) long and was larger than a modern elephant; a Pleistocene glyptodon (Doedicurus clavicaudatus) was more than four metres (13 feet) long and 1.5 metres (five feet) high. Both flourished in South America about 500,000 years ago. | ||
| 14.15.1 | External appearance | |
| Anteaters (Myrmecophagidae) have elongate
heads; tubular muzzles with no teeth; and long, sharp claws. Their toes vary in
number from two to four on the forefeet and from four to five on the hindfeet,
depending on the species. The thick coat of the giant anteater is gray with
lateral white-bordered blackish stripes, and the hair is long and straight,
especially on the characteristically stiff bushy tail. Tamanduas, or lesser
anteaters, have short hair, which is usually cream-coloured to brownish, with a
black vestlike area over the upper thorax. The entire underside of the tail, as
well as the tip, is naked. The two-toed anteater (Cyclopes) has soft silky fur,
usually golden yellow in colour. In this species, only the underside of the
prehensile tail is naked. Males and females are of approximately equal size in
Cyclopes and Tamandua, but males are much larger in Myrmecophaga. All anteaters
have enormously developed salivary glands that supply the sticky saliva that
covers their long extrusible tongues.
The shaggy pelage of tree sloths grows from the belly toward the back on the body and toward instead of away from the body on the limbs (i.e., downward, when the animal is suspended beneath a branch), thus facilitating the shedding of rain. Tree sloths have pale faces with darker eye rings. The body hair is yellowish to brownish, but the individual hairs are fluted and contain a growth of algae that gives a greenish cast to the entire animal, especially in the rainy season. In the drier conditions of captivity, the algae die and the animal loses the natural coloration. The legs are long, with the forelimbs longer than the hindlimbs, and are designed for suspension of the body rather than for "column-like" support. Armadillos are characterized by a dorsal bony carapace made up of scapula (shoulder), dorsal, and pelvic shields, separated by a series of movable bands. A bony cephalic (head) shield is also present. The tail is typically armoured as well, except in the naked-tailed armadillos of the genus Cabassous. The body hair is greatly reduced, but some, such as the pink fairy armadillo, have dense fur on their sides and underparts. A sparse growth of hair also occurs among the bony plates of all species. |
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