On Carnegie Hill and University Hill above the Niobrara River near Harrison, Nebraska, on what was James and Kate Cook’s Agate Springs cattle ranch, lie some of the best Miocene mammal fossils anywhere, 20 to 16.3 million years old. From 1904 to 1923 teams from the Carnegie Museum, the American Museum of Natural History, Yale and others competed here, because the hills gave up whole skeletons of animals known before only from fragments: the pony-sized rhinoceros Menoceras, the most common animal in the beds, the two-horned rhino Diceratherium, bear dogs, the giant pig-like Daeodon, gazelle-like and giraffe-like camels, the chalicothere Moropus, and land beavers, Palaeocastor, whose corkscrew burrows are known as Daemonelix. Why so many died in one place is still argued: a drought that crowded herds around the last water, carcasses swept into river bends and eddies, or quicksand. The monument, established in 1997, also keeps the Cook family’s collection of more than 500 Plains Indian artifacts.
Complete Miocene mammal skeletons and corkscrew burrows · Miocene, 20-16.3 mya
This ground is protected. Photograph it, record it, leave it where it lies. On US federal land the Paleontological Resources Preservation Act 2009 makes collecting vertebrate fossils an offence, and penalties are real.
Other places on the map within a couple of hours.
