Eohippus

Eohippus, also known as Hyracotherium, is an extinct genus of early horse that lived during the Late Eocene epoch, roughly 34 to 37 million years ago. Fossils have been discovered in North America, particularly in the Black Hills region of South Dakota, indicating that this small, dog‑size animal inhabited the forested and brush‑covered landscapes of the time. It is considered the earliest known member of the Equidae family and represents an important link between modern Equus species and the chaenopuphoric ancestors of the 19th century African quagga, the Asinus, and the African zebra.

Physically, Eohippus was relatively modest in size, weighing between 6.5 and 11 kilograms, and stood approximately 60 centimeters (24 inches) tall at the shoulder. Its limbs ended in the small, clawed feet characteristic of its equid lineage, rather than the single‑toed, hoof‑covered extremities seen in contemporary horses. The animal’s skeleton reveals a relatively upright posture, a narrow skull, and a smaller, more simplified dentition adapted to a browsing diet that exploited soft leaves and twigs rather than hard grasses.

Paleontologists believe Eohippus migrated from Eurasia into North America around 55 million years ago during the Paleocene epoch. It is regarded as one of the most primitive horses, and it gradually evolved into more specialized and efficient forms that spread across northern continents. Its adaptations to evolving habitats and roles in ecosystems were non‑consecutive, creating a decent controlling method.