xxm. 5 FOSSIL PROSIMIANS 613 



The Lorisformes (Fig. 390) include the slow lorises and other lemur- 

 like animals that are found outside Madagascar. They are known as 

 fossils back to the Miocene. The slow lorises (Nycticebus and Loris) of 

 India and Ceylon are arboreal and nocturnal, proceeding by remark- 

 ably slow and deliberate movements and often hanging upside down. 

 They eat fruit or small animals. Lorises also show some features that 

 recall the higher primates, for instance the tympanic ring is fused to 

 the petrosal bulla. In some of them the face is shorter and the brain- 

 case rounder than in true lemurs. It is therefore possible that they 



A 



(x4) 



(x3) 



Fig. 392. Dentition of Plesiadapis anceps. A. Right upper teeth showing 

 P 3 P 4 and 3 molars. B. Lower dentition. (After G. G. Simpson.) 



are survivors of an earlier stock, closer to our own than are the lemurs, 

 and some of the features, such as procumbent incisors, may be 

 developed independently in the two groups. However, traces of very 

 early features remain, including a transverse skin fold on the abdomen 

 of the female, which is considered by some to represent a marsupium. 

 On the African mainland there are also two successful genera of this 

 type, Galago, the bush baby (Fig. 391), and Perodkticus, the potto. 

 The former are jumping animals and can leave the trees; their 

 elongated tarsus somewhat recalls that of Tarsius. 



5. Fossil Prosimians 



The earliest primates of the Palaeocene and Eocene were insecti- 

 vorous and fruit-eating animals. They may be distributed among five 

 families, whose relationships are difficult to decide. The *Plesiadapidae, 

 from the Paleocene and Eocene of both Old and New Worlds, had 

 large upper and lower incisors and have been considered as related 

 both to tree-shrews and to the aye-aye (Fig. 392). They are probably 

 too specialized to be directly ancestral to either the lemurs or higher 



