Most of the extinct mammals in the Western Science Center's collection are Pleistocene Ice Age creatures, such as mastodons, Columbian mammoths, bison, camels, horses, and giant ground sloths, dating to between 50,000 and 14,000 years ago. Today's Fossil Friday is a much older extinct mammal, dating back to around 30 million years ago, a slice of geological time known as the Oligocene. This is the skull of an oreodont, a totally extinct group of even-toed ungulates (Artiodactyla) related to camels.This particular skull was discovered in 1963 in South Dakota by renowned local fossil hunter Harley Garbani and donated to the Western Science Center by his wife, Mary. Oreodonts were extremely abundant and diverse plant-eaters in the Oligocene of North America. This skull belongs to an oreodont called Merycoidodon, which was extremely common in South Dakota at this time.