400 ORIGIN OF LIFE IN AMEEICA 



remarkable and instructive examples of convergent develop- 

 ment among mammals. Finally the Santa Cruz beds contain 

 the remains of monkeys of South American type. The earliest 

 traces of mammalian remains in Patagonia were supposed to 

 have been found together with the bones of dinosaurs. Since 

 these reptiles are characteristic of the Mesozoic Era, the state- 

 ment that they were contemporaneous with rather advanced 

 types was at first treated with little credence, especially as 

 the actual deposits were not examined by Dr. Ameghino * 

 but by his brother. Dr. Both, however, has since re-examined 

 the localities in question and has met with mammalian re- 

 mains partly mixed with those of dinosaurs, and partly resting 

 actually below the latter, so that there is scarcely any doubt 

 as to the correctness of the original observation. The 

 mammals belong to peculiar mastodon-like ungulates, having 

 been placed in the order Pyrotheria which is now extinct and 

 quite confined to Patagonia. Others, such as Notostylops, be- 

 long to the Toxodontia above alluded to. 



I think there is a general agreement now that, at any rate 

 at the dawn of the Tertiary Era, a number of rather 

 specialized groups of mammals lived in Patagonia, and, 

 although some of them became extinct, others continued 

 to inhabit the country until recent geological times. A few 

 of the largest edentates, like the giant ground sloth Mega- 

 therium, which was about the size of an elephant, and is 

 supposed to have dragged down trees in order to feed on the 

 leaves, rather than climb up like its modern diminutive rela- 

 tion the tree-sloth, still roamed about the country in 

 Pleistocene times. f A few years ago the dried skin, with hair 

 still attached to it, of a huge creature was discovered in a cave 

 in southern Patagonia, near the boundary between Argentina 

 and Chile. It proved to belong to the ground sloth Neomy- 

 lodon, now known as Grypotherium listai.J Later on, the 

 bones of the animal were disinterred, along with those of an 

 extinct horse and a large carnivore. Traces of a fire were 

 also noticed and an enclosure with cut hay. From these evi- 



* Ameghino, Fl., "Formations sedimentaires," p. 80. 



t Lankester, Bay, " Extinct Animals," p. 172. 



t Moreno, F. P., and A. Smith Woodward, "Neomylodon listai." 



