Agate Fossil Beds National Monument

A large fossilized waterhole with hundreds of skeletons is preserved today in the Niobrara River valley at Agate Fossil Beds National Monument. The discovery of this deposit and others nearby in the early 1900s was important to the developing science of paleontology. The study of these fossils – then and continuing today – has helped answer questions about the past. But what were the conditions that created this drought and brought these animals together?

Fossils at Agate Fossil Beds

All of the animals whose fossil remains have been found here at Agate Fossil Beds are now extinct, but some are represented today by a few relatives and, rarely, by descendants. Palaeocastor had powerful clawed forelimbs for efficient digging and long, curved teeth like modern beavers. Herds of Stenomylus – small gazelle-camels about two feet tall – grazed in the grasslands beside the three-toed, pony-sized rhinoceroses, Menoceras. The most common mammal in the bonebed, Menoceras may have roamed these plains in herds. Only a few oreodonts, about the size of a sheep, have been found at Agate, and they are most common in the carnivore dens nearby, where they were the prey of beardogs. Fossil remains of the ancestors of the modern horse – Parahippus – also have been found in the waterhole but are rare. Horses became extinct in North America  and did not return until brought back by the Spaniards. Moropus was quite a fantastic animal. Related to both the horse and rhinoceros, it was large, had back legs shorter than the front, and had great claw-like hooves. It probably browsed on leaves of bushes and small trees. Another large animal that once lived here was Dinohyus, a giant entelodont related more closely to cows and pigs than to carnivores. This huge scavenger – whose skull alone was about three feet long and whose tracks have been found in the waterhole mud – broke bones with its enormous teeth (its bite marks occur on chalicothere limb bones). Discoveries in the 1980s include the fossil remains of beardogs and other carnivores and their dens, one of the few paleontological sites of this type in the world.

Paleontology: The Discovery of the Fossils

Most of the land that is now Agate Fossil Beds National Monument was once part of Agate Springs Ranch owned by James and Kate Cook. They bought the ranch from her parents in 1887, a few years after they had found "a beautifully petrified piece of the shaft of some creatures leg bone." In 1892 Erwin H. Barbour of the University of Nebraska was the first scientist to examine the strange Devil’s Corkscrews at Agate, later recognized as the fossilized burrows of the Palaeocastor. In August 1904, O.A. Peterson of the Carnegie Museum in Pittsburgh discovered the great bonebed with the help of Harold J. Cook, son of James Cook. Scientists from Yale University, the American Museum of Natural History in New York City, and other institutions also worked at these fossil beds, primarily between 1904 and 1923. Competition to find the best bones was mostly cordial, but on occasion grew spirited. These efforts formed outstanding collections in museums around the world.

Visiting Agate Fossil Beds along the Niobrara River

Besides protecting the fossil beds, the national monument forms an island preserve within a sea of sparsely settled ranchland; occasional windmills and cattle dot the horizon. The shortgrass prairie and marshland along the Niobrara River also harbor a rich animal and bird life. Wildflowers splash color across the hills in the spring. In all seasons the windswept North American prairies are reflected in the quiet beauty of vast sky and rolling land.

The Cook Collection of Indian Artifacts

James H. Cook, a noted frontiersman, big game hunter, and scout before settling on the Niobrara, first met Chief Red Cloud in 1874 when Prof. Othniel C. Marsh of Yale University appeared in western Nebraska looking for fossils. The Oglala Lakota (Sioux) were suspicious of Marsh, for they had only known of white men who came looking for gold. "Captain" Cook helped convince Red Cloud and the other Oglala that Marsh was indeed what he said he was. Over the years Cook helped the Oglala and Cheyenne on many occasions, and a steadfast friendship developed between the Cook family and the Indians, who brought them many gifts and told them stories concerning individual items. Today the collection belongs to the park. Pictographs painted on hides – one of a buffalo hunt and one of Custer’s Last Stand – saddles, bows, shirts (among them one of Red Cloud’s that he gave to the Cooks), moccasins, bags, war clubs, pipes, and guns make this collection an outstanding assemblage of Plains Indian culture; many are on display. James’ son, Harold, due to his interest in fossils, became very involved in paleontology. He also published many papers and participated in other important scientific research. Besides his father’s collection, other natural history specimens, Harold Cook’s paleontological library, the family correspondence, books, and papers spanning four generations are all preserved and available to researchers.