Idaho State Fossil
Hagerman Horse (common name)
Equus simplicidens (scientific name)
Equus simplicidens is an extinct species of horse that lived in the Pliocene epoch, approximately three to four million years ago, in what is now the western United States. The Hagerman horse has the distinction of being the earliest record of Equus, the genus that includes all modern horses, donkeys, and zebras. The Hagerman horse is the earliest known representative of what would eventually become the animals familiar today.
The largest concentration of Equus simplicidens fossils in North America can be visited at Hagerman Fossil Beds National Monument in Hagerman, Idaho. The park has 30 complete horse fossils and portions of 200 individual horses, making it the largest sample of this extinct species from one locality. In 1988, Hagerman horse became Idaho’s state fossil and Hagerman Fossil Beds became a national monument.
This species was first scientifically described in Hagerman, Idaho, in 1929 by Smithsonian paleontologist James W. Gidley. Gidley initially gave this species the name Plesippus shoshonensis before paleontologists recognized it to be the oldest species of the genusEquus and changed the name.
Although there is no fossil evidence of stripes, the pattern of the chewing surfaces of the teeth, as well as the details of the skull and rest of the skeleton, indicate that this animal was more closely related to the living Grevy’s zebra of east Africa than to horses. Hagerman horses were about the size of the present-day Arabian horse, and had a single hoof. Equus simplicidens was approximately 40 to 60 inches (105–145 cm) tall at the shoulder and weighed 385 to 900 pounds (110 to 400 kg).
This horse lived with saber-toothed cats and mastodons on the grasslands near ancient Lake Idaho and on the floodplains created by the Bonneville Flood. Although it is not precisely known why so many animals died in such a small area, it is thought that an entire herd of these animals probably drowned attempting to ford a flooded river and were swept away in the current. Their bodies were then quickly buried in the soft sand beneath the water. Layers of sand, silt, and clay at least 600 feet thick preserved an excellent group of Pliocene fossils in what is now the Idaho desert.
Hagerman horses, like many other large North American mammals, became extinct about 10,000 years ago, just before the last ice age. The reason for this is unknown, but disease, climate change, and human predation are theories.
Elmer Cook, a cattle rancher in Hagerman, Idaho, first discoveredEquus simplicidens in 1928. He showed the fossil bones to Dr. H.T. Stearns of the U.S. Geological Survey, who sent them to equine specialist James W. Gidley of the Smithsonian Institution in Washington, DC. When the bones were identified as belonging to an extinct horse, the area where the fossils were discovered was excavated. A staggering three tons of specimens were sent to the Smithsonian. Thousands of fossils from along Idaho’s Snake River have since been found and studied. Equus simplicidens has also been found in other parts of the midwestern and western United States, as well as in Mexico.
After the extinction of Equus simplicidens, horses did not return to North America until the Spanish Conquistadors brought them from Europe in the late 1500s.
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|Author: World Trade Press|