Fig. 99.—Skull of Armadillo. Dasypus sexcinctus. × ⅔. ex.oc, Exoccipital; fr, frontal; max, maxilla; nas, nasal; par, parietal; peri, periotic; p.max, premaxilla; s.oc, supraoccipital; sq, squamosal; ty, tympanic. (From Parker and Haswell's Zoology.)
| Fig. 100.—Bones of the right manus of the Hairy Armadillo. Dasypus villosus. × ⅔. c, Cuneiform; l, lunar; m, magnum; p, pisiform; R, radius; s, scaphoid; td, trapezoid; tm, trapezium; u, unciform; U, ulna; I-V, digits. (From Flower's Osteology.) | Fig. 101.—Bones of the manus of the Great Armadillo. Priodon giganteus. × ⅓. a, An accessory carpal ossicle in front of the pisiform, which is not seen in the figure. Other letters as in Fig. 100. (From Flower's Osteology.) |
The skull in the Armadillos presents a number of likenesses to the other American Edentates.[[104]] The premaxillaries are small, but are larger in Dasypus than in Tatusia. On the other hand the lachrymals are larger in the latter. The zygomatic arch is complete, but there is no downward process as in the Sloths. In Tatusia (but not in Dasypus) the "short thick pterygoids add somewhat to the hard palate." This is clearly a beginning or a remnant of the quite crocodilian character of the palate of Myrmecophaga. In the cervical vertebrae we see the Whale-like character of fusion between individual vertebrae; and also, as in the Whales, the degree to which this fusion is carried out varies; two to four may be thus united. The additional articular facets upon the dorsal vertebrae have been already commented upon as a point of important likeness to other American Edentates. The dorsal vertebrae are commonly eleven in number, the lumbar being three. But in Priodon the numbers are twelve and two respectively. There are traces to be observed of the double-headed attachment of the ribs to the sternum. The shoulder girdle of the Armadillos is somewhat diverse in form in different genera; the acromion is always large, and is remarkable in Priodon for the fact that the humerus also articulates with it, its extremity being recurved, and forming a socket for this purpose. As in some other Edentates there is a second spine on the scapula behind the first. The clavicle is strong. There is some variation in the form of the manus. It is five-fingered in Dasypus; in Tolypeutes the first digit has vanished; on the other hand, in Priodon, the fifth has become rudimentary
and the third enormously enlarged. This latter fact recalls the arrangement characteristic of Myrmecophaga. The pelvis is greatly attached by the ischium to the vertebral column. The femur has a third trochanter.
The various forms of Armadillos are largely distinguished by the number of movable thin bands of scutes lying between the large anterior and posterior shields. Thus we have Dasypus sexcinctus, Tolypeutes tricinctus, etc.
Fig. 102.—Pelvis and sacrum of Armadillo. Dasypus sexcinctus. ac, Acetabulum; il, ilium; isch, ischium; obt.for, obturator-foramen; pect.tub, pectineal tubercle; pub, pubis. (From Parker and Haswell's Zoology.)
The little Pichi-chago (or, more correctly, Pichy-ciego), Chlamydophorus, which only grows to about 5 inches in length, has no movable bands at all. It is covered with a uniform series of plates, which, moreover, are not discontinuous at the neck. It differs, too, from the prevailing Armadillo-type by the absence of conspicuous external ears. In the anterior part of the body the armature consists of little more than the horny plates, which in other Armadillos overlie the bony dermal plates. In the hinder region the bony plates are strong. In this animal, therefore, we have the dermal armature reduced to a minimum; but it must be noticed that, like the extinct Glyptodons, the armature is continuous and nowhere ringed.