i62 EVOLUTION IN THE PAST 



Miocene species of ground-sloths failed to survive the Period ; 

 but it is probable that some of those of which remains have 

 been found (Prepotherium, Nematherium, Analcitherium) were 

 forerunners, if not actual ancestors, of some of the gigantic 

 ground-sloths of later times. 

 ARMADILLOS Armadillos of various types were about the land. Some 

 were very small animals (Prozaedius) ; others (Stegotherium, 

 Proeutatus) attained a length of two feet, and therefore nearly 

 rivalled in size the largest of armadillos now living. They 

 probably differed but little in appearance from existing forms ; 

 and Uke the latter their carapaces had movable bands, 

 enabhng the animals more or less to roll themselves up for 

 protection. 

 GLYPTODONTS Other forms, closely alhed to the armadillos, are known on 

 account of their " carved " or fluted teeth as Glyptodonts. 

 They differed in some parts of their anatomy from armadillos, 

 and were not, hke the latter, adapted for burrowing. Their 

 carapaces, moreover, were far less flexible. Except in a 

 few cases they did not exceed the biggest of the armadillos 

 in length, great though be the disparity in nomenclature 

 (PfopalcBohoplofhorus). Glyptodonts were destined to make 

 a mark in South American mammal Ufe ; and some of the 

 known Miocene forms (Metopoxotus) probably were ancestors 

 of the monster glyptodonts that subsequently appeared. 



No remains of ant-eaters or tree-sloths have been found ; 

 but ground-sloths had some strong points of resemblance to 

 tree-sloths, and also to ant-eaters. Ground-sloths, tree- 

 sloths, and ant-eaters, therefore, were probably all derived 

 from a common ancestry. Moreover, it is probable that at 

 one time there was a stiU older stock which held potentially 

 not those animals only, but also armadillos and glypto- 

 donts. 



Many kinds of creatures besides ground-sloths and arma- 

 dillos were at this time in South America. The most notable 

 of these were hoofed animals ; but it is not possible to bring 

 them into close line with any ungulates now living. 

 TOXODONTS Some of them are grouped together as Toxodonts, as the 

 typical forms had " bow "-shaped grinding teeth. These 

 strange animals were for the most part about the size of 



