

"^ 





Fig. 20.5. Reconstruction of selected genera representing significant stages in the evolution 

 of the horse family. A, Hyracothenum { = Eohippus), Eocene. B, Mesohippus, Oligocene. 

 C, Hippanon, Pliocene; this genus is not on the main line of evolution of modern horses. 



different, in fact, that without the fossil remains of numerous connecting 

 forms they probably would not be considered related at all. The evolution 

 of horses involved many independent lines, each culminating in different end 

 forms at different periods. The evolutionary sequence leading most directly 



626 



