March 1, 1894.] 



KNOWLEDGE. 



51 



THE MAILED MONSTERS OF ARGENTINA. 



By R. Lydekker, B.A.Cantab. 



AMONG all the extinct mammals of the Argentine, 

 none strike the beholder with more astonishment 

 than those gigantic cousins of the modem arma- 

 dillos of South America, collectively known as 

 glyptodonts ; their name being derived from the 

 peculiar sculpture with which the grinding surfaces 

 of their molar teeth are ornamented. In a previous 

 article, entitled " Armadillos and Aard-Varks," we 

 have already considered the leading characters of the 

 great or der of edentate mammals, of which the whole 

 of the typical representatives are characteristic of 

 South America, although a few of the extinct species 



however, the armadillos (exclusive of the aberrant 

 piehiciago, described in the article referred to) have a 

 larger or smaller portion of the middle region of the 

 carapace formed of movable transverse bands of plates, in 

 the glyptodonts the whole structure is welded into a single 

 piece. It must not, however, be supposed that this carapace 

 consists of a single solid dome of bone, as, if it did, there 

 would, of course, be no possibility of growth. On the 

 contrary, the carapace, as shown in the beautiful figure 

 taken from a photograph of the external skeleton of the 

 largest member of the group preserved in the museum at 

 La Plata, is composed of a number of polygonal or 

 rhomboidal plates articulating together at their edges, and 

 thus allowing of free growtli. In very old individuals a 

 considerable number of these plates may, however, become 

 completely fused together. During life these bony plates 



Fig. 1. — Internal Skeleton of the Smooth-tailed Glyptodont. 



wandered into North America during the Pleistocene 

 period. We have likewise pointed out how the armadillos 

 and their allies differ from the other members of the order, 

 and have likewise made some mention of the glyptodonts 

 themselves. There are, however, such great differences 

 between the various kinds of glyptodonts, which are sub- 

 divided into several genera, that the group will well repay 

 special investigation ; and, indeed, no adequate conception 

 of the extinct fauna of the " Land of Skeletons " could be 

 given without devoting a separate article to these most 

 curious animals. 



As we have already pointed out elsewhere, both arma- 

 dillos and glyptodonts differ from the other members of the 

 order to which they belong in having their bodies protected 

 by a bony shell or carapace, covering all but the under 

 parts ; the top of the head being covered by a similar bony 

 shield, while the tail is encased in a series of bony rings, or 

 in rings at the base and a long tube at the tip. Whereas, 



were covered with small horny shields, as in the living 

 armadillos ; and they frequently show incised lines formed 

 by the lines of union between such shields. For instance, 

 in the members of the typical genus of the group, or ring- 

 tailed glyptodonts, each bony plate was smooth and 

 polygonal in shape, while the lines indicating the borders 

 of the horny shields take the form of a rosette. Another 

 important point of difference from the armadillos is to be 

 found in the contour of the skull, which is short, deep, 

 and rounded, instead of being long, flattened, and pointed 

 at the muzzle. Then again, whereas the armadillos have 

 small cylindrical teeth, those of the glyptodonts are large, 

 and fluted at the sides, with their grinding surfaces marked 

 by the aforesaid sculpture ; while the whole series is in 

 close contact, and forms one of the most efficient grinding 

 machines imaginable. To support the enormous weight 

 of the carapace, which in some of the larger kinds is 

 considerably more than an inch in thickness, special 



