7 o4 PROTOUNGULATES xxvm. 8 



8. Order Tubulidentata 



The aardvark ('earth-pig') or Cape ant-eater, Orycteropus (Fig. 

 470), is a zoologically very isolated form, of unknown affinities, placed 

 by Simpson with the Protoungulata, because it is possibly not very 

 remote from the condylarths. It is the size of a small pig, with a highly 

 curved back, and is much given to digging, both for protection and to 

 obtain termites, which are its main food. It occurs from South Africa 

 to the Sudan. There is an elongated snout, round mouth, and long 

 tongue, as in other ant-eaters. The peglike teeth are unlike those in 

 any other mammal. They consist of numerous hexagonal columns 



1 



Fig. 470. Orycteropus, the aardvark. (From life.) 



of dentine, separated by tubes of pulp. There is no enamel, though 

 enamel organs are present in the tooth germs. In the adult there are 

 about five teeth in each jaw, but there is a full series of rudimentary 

 milk teeth. 



There are special arrangements in the mouth and throat to allow 

 the animal to bury its snout in a mass of termites and then to swallow 

 them while continuing to breathe. There are large salivary glands. 

 The digits (4 in hand and 5 in foot) are covered by structures some- 

 times referred to as compressed nails, sometimes as hoofs. There is 

 a strong clavicle and complete radius and ulna and tibia and fibula. 

 The limbs are thus specialized for digging, but retain the characters 

 of the earliest mammals. The head is long and the brain small and of 

 an extremely primitive type, with extensive olfactory regions and very 

 small neopallium. The olfactory turbinals are better developed than 

 in any other mammal; the aardvarks find termites by their scent. 

 The animals are nocturnal and the retina has only rods, and a tapetum. 

 The ears are long and hearing acute and there are bristles on the long 

 mobile snout. The uterus is paired and the placenta of a zonary type, 

 somewhat like that of carnivores. There is a very large allantois. 



