PLEISTOCENE PERIOD 205 



some cases as large as rhinoceroses (Toxodon). The guinea- 

 pig-shaped typotheres were also much bigger, some of the 

 animals having skulls a foot in length (T. cristatum). These 

 creatures had further converged to true rodents by the loss 

 of their canine teeth. Among the lama-hke litopterns, forms 

 were now to be seen as large as camels (Macrauchenia). In 

 the Pliocene Period some of the litopterns were remarkable in 

 having the nasal aperture much higher up the skull than in 

 the earlier forms. This shifting process had been continued, 

 and the aperture was now located between the eyes. This 

 leads one to suppose that a short trunk had been evolved. 

 Macrauchenia, the typical form, was, so to speak, playing 

 many parts. In bodily shape and the length of the neck it 

 resembled a lama ; its limbs — the fore being longer than the 

 hind — were suggestive of a giraffe ; its head resembled in 

 structure that of a horse ; its proboscis that of a primitive 

 elephant ; its teeth, those of a rhinoceros ; whilst its feet 

 were much as those of the primitive three-toed horses. 



There was thus in South America a remarkable medley of 

 animals savouring of primitive times in mammal evolu- 

 tion. The mosaic anatomj^ of Macrauchenia was quite out of 

 date. The dissipated constitution of toxodonts exhibited a 

 want of concentration almost as anachronic. Animals, small- 

 brained and heavily armoured— represented by glyptodonts— 

 had long been more or less condemned in other parts of the 

 world. Brain power had come well to the fore, and heavy 

 armour was being discarded. Had not man been evolved ?— a 

 well-brained creature with practically no armour to shield him 

 from his foes. It is, therefore, no matter for surprise that as 

 soon as South America became, as it were, opened up, a good 

 deal of the native fauna failed to hold its own. It was 

 victimised, in short, by what may be called mammal free 

 trade. Litopterns, toxodonts, typotheres, and glyptodonts 

 slowly passed away ; and are not known after this Period. 

 Carnivores from the north had, no doubt, much to do with this; 

 for to judge by the size of the " sabre-toothed " cats (Smilo- 

 don), and certain wolf-like animals (C. moreni), these brutes 

 were living well. Ground-sloths survived the other forms, for 

 they were certainly in existence when in later times man 



