VERTEBRATE PALAEONTOLOGY 145 



told. In fact one could easily discuss the evolution of the story of 

 the evolution of the horse. 



It started when Kowalevsky in 1874 working with European 

 and Asian forms drew up the scheme shown below. 



Equus (Pleistocene- Recent) 



HI 



Hipparion (Pliocene) 



t 



Anchitherium (Miocene) 



t 



Palaeotherium (Eocene) 



These fossil types showed the trends in the evolution of the 

 modern horse, i.e. increase in size of the body, reduction in the 

 number of digits, molarisation of the premolars, etc, even though 

 in fact later workers showed that Palaeotherium, Anchitherium 

 and Hipparion were not even on the main line to the evolution of 

 the horse. In particular, Kowalevsky was handicapped in studying 

 only Old World horses whilst it has been clearly shown by the 

 magnificent work of American palaeontologists such as Marsh, 

 Cope, Leidy, Osborn and Matthew that the major development 

 of the horse took place in the New World. In 1917 Lull published 

 a scheme showing the then current concept of the evolution of the 

 horse (Fig. 42). 



Further research showed that the situation was even more 

 complex than that illustrated by Lull and in 1951 the scheme 

 shown in Fig. 43 was a more accurate account of the evolution of 

 the horse ; it will be noted that instead of a simple direct line the 

 pattern has become more and more branched. 



To the interested non-specialist there are several things that are 

 puzzling in the accounts of the evolution of the horse. In the first 

 place it is difficult to find a critical account of the basic information. 

 The accounts given by Piveteau (1958) and by Matthew (1926) 

 are more concerned with the names of the intermediate forms and 

 the basic trends of evolution. The account given by Simpson 

 (1951) is of great interest and very readable but it is written for a 

 wider audience. It is necessary to go back to the references given 

 in Matthew (1926) or the papers of Matthew and Stirton (1930), 



