LIFE IN THE KAINOZOIC EPOCH 473 



of difference between the early kainozoic ancestors of Ungulates 

 and Carnivores, both of which undoubtedly sprang from the 

 same mesozoic stock, though this is as yet unknown. In similar 

 fashion we find that the lines of descent of recent Insect-Eaters 

 {Insectivora), Lemurs {Lemtiroidea), and Monkeys {Primates) 

 converge as we trace them back to the beginning of the epoch. 

 The branches of the genealogical tree of mammals corresponding 

 to the last two groups actually meet, and on this account some 

 experts would place the Lemurs in the same order as Monkeys 

 {Primates). We further find that the lines of descent of Insecti- 

 vores. Lemurs, and Monkeys converge towards those of the 

 Ungulates and Carnivores, and this appears to be also true for 

 the Mammals Poor in 

 Teeth {Edentata). Some 

 day, perhaps, we may be 

 able to trace back all 

 these six orders, together 

 with Conies and Ele- 

 phants, to common meso- 

 zoic ancestors. 



Whales, &c. {Cetacea), 

 \^ea - C^OTJOs ( izrenxa ) 



\ /' Fig. 1332. — Skeleton of Phenacodus (reduced) 



Gnawers {Rodentia), and 



Bats {Chiroptera) seem to have acquired their typical characters 

 before the Kainozoic epoch began, and we are not yet able to 

 trace them back to the main line of mammalian descent. The 

 two first groups, and creatures of the seal kind, replaced the 

 marine reptiles of Mesozoic time in the life of the sea, and the 

 Flying Reptiles proved unable to maintain their supremacy against 

 the competition of Bats and Birds. 



In the later part of the Kainozoic epoch certain orders of 

 mammals were represented by relatively gigantic forms. A 

 good instance of this is afforded by certain extinct American 

 representatives of the Mammals Poor in Teeth {Edentata). At 

 this time South America and the southern part of the sister 

 continent were inhabited by huge Ground -Sloths, of which one 

 typical form {Megatherium) was at least as large as an elephant. 

 It and its allies combined some of the structural features of exist- 

 ing Sloths and American Ant- Eaters. That so large an animal 

 as the one mentioned was not a climber is sufficiently obvious. 



