took about 55 million years for the Equus Family
(see the "Some Information" section)
to evolve from their earliest horse-like ancestor,
which lived during the Eocene period. That animal,
though first called Eohippus, is now named Hyractotherium.
It was not much larger than a hare. It was a "browsing"
animal - unlike the today's horses, it was feeding
on leaves and shrubs. Also, it had paw-like feet
with four-toed forefeet, and three-toed hind feet.
What is a horse's hoof? It's a toe which is
what we call a "hoof" nowadays, but it
used to be three - the middle one, and the other
two grown into the leg. So the Hyractotherium's
feet reminded that of a rodent, and its low-crowned teeth
were made for "browsing". The Hyractotherium
is believed to have an appearance of a big
guinea pig with a donkey's tail, and stripes along
the Hyractotherium evolved into the Mesohippus.
It was much the same, except it had three-toed feet,
no stripes, and its teeth were suited slightly more
for grazing. It was about the size of a sheep, and
it had lived during the Oligocene period about 37
million years ago.
next horse was Parahippus. It hadn't changed much
in any way, except for the two side toes of each
growing deeper into the leg, and the horse growing larger.
then came the Miocene period (about 20 million years
ago) and many of the woodlands became grasslands.
Adapting to this environmental change, the horses
had developed longer legs in order to run across
a large area in search of pasture and to escape
from predators. Furthermore, their teeth became
high-crowned in order to adapt to the new diet.
The first grazing horse was the Merrychippus, which
then became the Pliohippus - the first one-toed
horse. After that, came the Pleistocene period (about
two million years ago), which gave rise to the Equus
- the nowadays horse.