As we circulate to the this new Oligocene, horses beginning to change. The fresh new climate out-of United states is actually become drier, and you can grasses were simply developing. The fresh big woods was in fact beginning to shrink. The fresh new late Eocene horses replied by development harder teeth and you can become a while larger and leggier (to have ideal rates out in new discover).
The fresh types Mesohippus celer looks all of a sudden throughout the later Eocene, approx 40 My (such as for instance abrupt speciations can happen whenever a population experiences the new choosy forces and you will/otherwise will get remote throughout the moms and dad varieties.