146 



VERTEBRATE PALAEONTOLOGY 



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Equus 



Hipparion 



Pliohippus 



Hipparion 



Protohippus 



Onohippidion 



Hippidion 



Anchitherium 



Merychippus 



Hypohippus 



Miohippus 



Mesohippus 



Epihi 



Dpus 



Orohippus 



Hyracotherium = Eohippus 



Fig. 42. Evolution of the horse. The scheme shown here is more 

 complex than that suggested by Kowalevsky. (From Lull 1918.) 



and Osborn (1905, 1918) to get any satisfaction concerning the 

 fossils themselves. 



What does the sceptical reader hope to find out? It takes a 

 great deal of reading to find out for any particular genus just how 

 complete the various parts of the body are and how much in the 

 illustrated figures is due to clever reconstruction. The early 

 papers were always careful to indicate by dotted lines or lack of 

 shading the precise limits of the reconstructions, but later authors 

 are not so careful. Secondly it is difficult to find out just how many 

 specimens of a given genus are available for study. Thus it is 

 one thing to know that our information on Hyracotherium is 

 based on, say, 500 specimens, and another if our information is 



