740 



GENETICS AND EVOLUTION 



320. The Anthropoids 



Monkeys, apes and man, which have many characteristics in com- 

 mon, are grouped in the suborder Anthropoidea. The anthropoids have 

 larger, more complicated brains, and large, forward-directed eyes en- 

 closed in complete bony sockets. Most of the anthropoids walk on all 

 lour legs, but tend to sit upright, so that the hands are free to manipu- 

 late objects. The opposability of the thumb and great toe is highly de- 

 veloped. 



The anthropoids are subdivided into two groups, the more primitive 

 platyrrhine or broad-nosed monkeys of South and Central America, and 

 the catarrhine or narrow-nosed forms, which include the Old World 

 monkeys, apes and man. 



The platyrrhines, which have widely separated nostrils directed for- 

 ward and sideward, are a group of primates which became isolated in 

 South America during the Tertiary and evolved independently of the 

 other anthropoids. They include the marmosets, which are primitive and 

 resemble lemurs in general body form, and the capuchin, squirrel and 

 spider monkeys, most of which have strongly prehensile tails which serve 



as "fifth hands" in climbing (Fig. 36.3). 

 The catarrhines have a much nar- 

 rower nose, with nostrils set close 

 together and directed downward. They 

 all have the same dental formula, a 

 large brain, flattened nails on all digits, 

 and a tail which may be long, short or 

 absent, but is never prehensile (Fig. 

 36.4). 



The oldest fossil catarrhine is 

 Parapithecus, whose remains have 

 been found in the lower Oligocene in 

 Egypt. It was a small monkey and is 

 believed to represent the common 

 ancestor of today's Old World mon- 

 keys, apes and man. The present-day 

 Old World monkeys are a large group, 

 which includes the macaque, guenon, 

 mandrill, mangabey, baboon, langur 

 and others. They all tend to sit up- 

 right and have buttocks with bare, 

 hardened sitting pads, called ischial 

 callosities, which are frequently a 

 brilliant red or blue. The mandrills 

 and baboons have taken to living on 

 the ground and walking on all fours. 

 They have an elongated snout and 

 large canine teeth. Baboons are intel- 



.J''^,T ^*;^- ^Pi'^'^'' monkey, a New jj animals that travel in troops 



World monkey with a strong prehensile ^ • i • • r i j 



tail, used in swinging from tree to tree, ^nd cooperate m obtammg food and 



(Courtesy of the San Diego Zoo.) protecting the females and young. 



