Edentata, a small group of mammals, elevated into an order by Cuvier, and associated rather by negative than positive characters; these are, a partial or total absence of teeth, the possession of very large claws embracing the ends of the toes, and a general slowness of motion arising from the organization of the limbs. One group consists of strictly vegetable feeders, the tardigrada of Illiger, including the sloths (bradypus, Linn.); the other group is principally insectivorous, including the ant-eater (myrmecophaga, Linn.), the armadillo (dasypus, Linn.), the pangolin (ma-nis, Linn.), the aard-vark (orycteropus, Geoff.), and the gigantic fossil megatherium. The term edentata, or toothless animals, is not properly applied to any of the group except the ant-eaters and the pangolins. The sloths are fitted for a life among the branches of trees, which they rarely leave unless in search of fresh food, and then in the slowest and most awkward manner; the ant-eaters dig up their insect food with their powerful claws, and entrap them on their glutinous tongues; the armadillos, with their hard external covering, pursue insects on the ground, dig after vegetables and roots, and eat even decaying carcasses.
The skull in the sloth is very short and round, in the armadillo longer and pointed, and in the ant-eater much elongated; in the megatherium there is a return to the short and solid skull of the sloth, and this animal seems in many respects intermediate between the tardigrada and the true edentata. The spine varies in the length and firmness of its parts, according to the habits of the animal; the neck is long and capable of great rotation in the sloth, the two upper dorsals being so modified that they perform the functions of cervi-cals, with rudimentary ribs; the dorsal portion is very long, and contains more vertebrae than in any other mammalian group, viz.: 16 in the great ant-eater, 14 in the three-toed and 23 in the two-toed sloth; the ribs are remarkably broad, overlapping each other near the spine in some of the ant-eaters, giving thus great solidity to the chest and the necessary support for the digging fore limbs; the lumber vertebrae are broad, with strong spinous, transverse, and articulating processes; the caudal vertebrae are 7 or 8 in the sloths, 40 in the great ant-eater, 45 in the long-tailed pangolin, and at least 18 in the megatherium; the V-shaped bones on the inferior surface are well developed in the true edentata, and in the megatherium; the anterior bone of the sternum is considerably developed in the whole group, especially in the ant-eaters and armadillos.
The pelvis in the sloths and the megatherium is wide and capacious, and the ilia very broad; in the true edentates it is elongated, with the acetabulum behind the middle, and the ilia are very long. In the latter the anterior limbs are formed for digging, and therefore the scapular arch is well developed, the humerus short and robust, with strongly marked processes for muscular attachments; a clavicle is present in the ant-eaters and armadillos, but absent in the pangolins; the forearm has so large an olecranon that the ulna is nearly or quite twice the length of the radius; the bones are robust, and the hand is remarkable for the unequal size of the fingers, the middle one being in most of them much the largest; the peculiarities of the posterior limbs are less remarkable. Another reason for separating the tardigrades from the edentates is found in the digestive apparatus. In the former the teeth are simple, formed for bruising leaves and stems; the stomach is complicated, divided into numerous compartments by internal folds, somewhat like the stomach of ruminants; the large intestine is readily distinguished by its size from the small, and by their partial separation.
In the edentates, the teeth when present are simple, more numerous, and formed for crushing insects; the stomach is far less complicated, and the division into small and large intestine is not well marked. The peculiar subdivision of the arteries of the limbs in the sloths is not required in the active and terrestrial edentates; and the investing armor of the armadillo and the pangolin would be equally unnecessary for the arboreal tardigrades. The edentata seem to establish the passage from the unguiculata to the ungulata, as the nails are greatly developed, and cover in a great degree the ends of the fingers. That which especially characterizes them is the absence of teeth in the anterior portion of the jaws, the dental apparatus being in most reduced to molars and canines.