The tapirs are an ancient family which has changed but little since it separated from the other perissodactyl stocks in the early Tertiary.
"The Elements of Geology"
William Harmon Norton
This is because of our still very incomplete knowledge of several perissodactyl genera of the Eocene, any one of which may eventually prove to be the ancestor sought for.
"Darwin and Modern Science"
A.C. Seward and Others
As I said above, the primitive Ungulate soon branches into three types which dimly foreshadow the tapir, the horse, and the rhinoceros, the three forms of the perissodactyl.
"The Story of Evolution"
Joseph McCabe