Every horse you’ve ever encountered – from the Budweiser Clydesdales to Kentucky Derby race horses to three-foot-tall “miniature horses” – are members of the same species, Equus caballus. In fact, there are only seven species of the family that includes horses, zebras, and donkeys – Equidae – alive today. But there used to be many, many more.
Living members of Equidae include the horse (wild or domestic), the donkey, the ass, the kiang, the Przewalski horse, and three types of zebras. Two subspecies of equids, the Quagga (Equus quagga quagga) and the Tarpan (Equus ferus ferus), went extinct relatively recently, in 1883 and 1909 respectively. The closest living relatives to the Equidae family include the rhinoceros and the tapir.
During the Pliocene, however, even more horse-like species trotted the Earth. Raymond L. Bernor of Howard University, Henry Gilbert of California State University, Gina M. Semprebon of Bay Path College, Scot Simpson of the Cleveland Museum of Natural History, and Sileshi Semaw of the Centro Nacional de Investigación sobre la Evolución Humana in Burgos, Spain, detailed the discovery of a new species of ancient horse in their paper published last November in Journal of Vertebrate Paleontology.
The discovery was made in the desert of Ethiopia. “Among the many fossils we found,” says Professor Scot Simpson, “are the two ends of the foreleg bone – the canon – brilliant white and well preserved in the red-tinted earth.” After two expeditions, Bernor and his associates had collected enough fossil evidence to recognize they had discovered a new species of horse. They named it Eurygnathohippus woldegabrieli.
Eurygnathohippus woldegabrieli lived about 4.4 million years ago. It’s long, slender leg bones indicate that it could make a quick getaway from its lion and hyena-like predators. Its long, worn teeth indicate that it grazed on grasses just like the horses that we are familiar with today. Other early species of horses ate leaves or shrubs instead of grass and were small enough to hide from predators in the woodlands instead of outracing them on the plains.
Bernor and his associates hope that understanding the ancient horses of Ethiopia will help paint a better picture of what the grasslands and woodlands of Africa were like for human ancestors over four million years ago.
Bernor, R. L., Gilbert, H., Semprebon, G. M., Simpson, S., & Semaw, S. (2013). Eurygnathohippus woldegabrieli, sp. nov.(Perissodactyla, Mammalia), from the middle Pliocene of Aramis, Ethiopia. Journal of Vertebrate Paleontology, 33(6), 1472-1485.
The Paleontological Research Institution, Ithaca, New York, is pleased to sponsor Paleontology content for This View of Life. Founded in 1932, PRI has outstanding programs in research, collections, and publications, and is a national leader in development of informal Earth science education resources for educators and the general public.