You see... I do not care. But if you need me to pick.
Show me what a horse used to be. It started as goop. Walk me through its evolution. Show me the links.
Horses? Okay.
The first animals that we would call horses lived about 10 million years ago. You can read about the evolution of these early horses to modern forms
here.
They are members of the odd-toed ungulateswhich have members in three groups today, as described below:
ORDER PERISSODACTYLA
Suborder Hippomorpha
Family Equidae: horses and allies, seven species in one genus
Wild horse, Equus ferus
Przewalski's Horse, Equus ferus przewalskii
Domestic horse, Equus ferus caballus
African Wild Ass Equus africanus
Domesticated Ass (Donkey) Equus africanus asinus
Onager or Asiatic Ass, Equus hemionus
Kiang or Tibetan Wild Ass, Equus kiang
Plains Zebra, Equus quagga
Mountain Zebra, Equus zebra
Cape Mountain Zebra, Equus zebra zebra
Hartmann's Mountain Zebra, Equus zebra hartmannae
Grevy's Zebra, Equus grevyi
Suborder Ceratomorpha
Family Tapiridae: tapirs, four species in one genus
Brazilian Tapir, Tapirus terrestris
Mountain Tapir, Tapirus pinchaque
Baird's Tapir, Tapirus bairdii
Malayan Tapir, Tapirus indicus
Family Rhinocerotidae: rhinoceroses, five species in four genera
Black Rhinoceros, Diceros bicornis
White Rhinoceros, Ceratotherium simum
Indian Rhinoceros, Rhinoceros unicornis
Javan Rhinoceros, Rhinoceros sondaicus
Sumatran Rhinoceros, Dicerorhinus sumatrensis
The odd toed ungulates evolved from earlier groups, as you can see in the diagram about halfway down
this page. They stem from a group of placental mammals called the
Laurasiatheres, which in turn evolved from a group called
Eutheria, which is the name given to the all placental mammals.
You can see a diagram of how mammals in general evolved from earlier groups
here.
Therapsids themselves evolved from the
Sphenacodonts, which include the well-known Dimetrodon.
Before then, the lineage can trace its line through reptiles, amphibians and fish, then through earlier invertebrate life forms before its origin at the dawn of life.