Off to the Races

Over millions of years in North America, horses adapted as woodlands changed to grasslands, gradually evolving from dog-sized primitive horses into the lineage that led to the modern-day horse. Mesohippus was the first three-toed horse, while ancestors of earlier horses had five toes, and this adaptation gave Mesohippus a greater chance of survival on open scrublands. Mesohippus, a three-toed horse and an ancestor of the modern-day horse, lived here in open woodlands 30 to 37 million years ago.

South Dakota · United States