284 LAND MAMMALS IN THE WESTERN HEMISPHERE 



were represented by species which differed but shghtly from 

 those of the present. The grasses were already in existence, 

 but, there is good reason to believe, they had not attained 

 to much importance and did not cover the plains and open 

 spaces as they did in the Miocene and still continue to do. 

 As the grasses afford the principal food-supply of so many 

 grazing animals, the matter of their abundance and extension 

 is a very significant one in the history of mammalian develop- 

 ment, and, as we have already learned, eventually led to wide- 

 spread and profound modifications of structure, especially of 

 the teeth. While there is thus nothing very strange about 

 the plant-world of Paleocene times, the higher animal life was 

 almost totally different from that of modern times and made 

 up a most curious and bizarre assemblage, from which nearly 

 all the familiar Recent types were absent. The reptiles had 

 been greatly impoverished by the world-wide and, as yet, un- 

 explained destruction which overtook them at the end of the 

 Mesozoic era, but it is possible that in both North and South 

 America a few of the huge Dinosaurs survived the decimation 

 of the class. Very characteristic of the Paleocene in North 

 America and Europe were large, lizard-like reptiles, allied to 

 the New Zealand Tuatara, while crocodiles and tortoises 

 abounded ; snakes were present, but do not appear to have 

 been very common. 



It is the mammals which were the strangest element of 

 Paleocene life, and our imaginary observer would find no 

 creature that he had ever seen before. The difference from 

 modern mammalian life was not merely one of species, genera 

 or even families, but of orders, for only one, or at most two, 

 of the orders now living were then to be found in North America, 

 and both of these (marsupials and insectivores) were primitive 

 and archaic groups, which seem like belated survivals in the 

 modern world. There were no rodents, or true carnivores, no 

 lemurs, monkeys, artiodactyls, perissodactyls or proboscideans. 



In the Torrejon, or upper Paleocene, there were many 



