This impressive fossilized horse head comes to us preserved from China during the Oligocene epoch. Over thirty million years ago, the Oligocene saw the start of global cooling that would eventually shift the earth’s climate to one where glaciers were present and ice ages were possible. Grasslands expand and tropical forests shrank. Animals evolved to fit the new, open landscape and many fast-running prey and predator species arose as a result. Horses have been racing across the land for 50 million years – much longer than human beings. Of all colours, shapes and sizes, some larger than a small dog. Multiple horse species lived at the same time, often side by side. The size and distinct shape of the skull indicates that the prehistoric horses would have been quite unrecognizable to Equus genus that includes all extant species, which represent just one tiny twig on an immense family tree that spans millions of years. All the other branches of the horse family, known as Equidae, are now extinct. By 55 million years ago, the first members of the horse family, the dog-sized Hyracotherium, were scampering through the forests that covered North America. For more than half their history, most horses remained small, forest browsers. But changing climate conditions allowed grasslands to expand, and about 20 million years ago, many new species rapidly evolved. Some-but not all-became larger and had the familiar hooves and grazing diets that we associate with horses today. Only these species survived to the present, but in the past, small and large species lived side by side.
Then, about 35 million years ago, global temperatures dropped, creating a climate more similar to todays. Thereafter, dry grasslands replaced much of the North American forest, leading to rapid evolution among horses. By about nine million years ago, most forest browsers had disappeared, leaving primarily grass-eating grazers like those alive today.
The majority of horse species evolved in North America. From there, they occasionally walked to other continents. About 20 million years ago, three-toed horses called anchitheres crossed to Asia and continued to Europe and Africa. About 11 million years ago, three-toed horses called hipparions spread from North America around the globe. About three million years ago, hoofed Equus, the ancestor of living horses, spread to several continents including South America.
Scientists from China’s Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) discovered by a skull fossil of a Hipparion – a three-toed horse with long nose that lived approximately five million years ago in February 2012. The very well preserved fossil skull was found in the northwestern province of Gansu, at a location where many mammal fossils have been discovered in recent years. They are useful to scientists in determining the evolution of man’s trusted friend. The publishing of this new discovery coincides with the release of another study into prehistoric horses published by researchers at the Florida Museum of Natural History (Florida University).