In 1904 the first scientific excavation discovered the fossils of a rhinoceros unknown to science. Sharing the plains with the small two-horned rhino were the Moropus, a mammal with the head of a horse, neck of a giraffe and clawlike hooves; the Dinohyus, a huge tusked piglike scavenger; and the Stenomylus, a small camel similar to the gazelle that traveled in great herds.
Such familiar animals as mule deer, coyotes, cottontails and prairie rattlesnakes now roam the grassy area. Plants include prairie sand reed, blue grama, little bluestem and needle-and-thread grasses as well as lupine, spiderwort, sunflower and soapweed prairie flowers.
A visitor center and museum presents exhibits of fossils and paleontological research tools as well as a 12-minute movie. Native American artifacts, including beaded moccasins, catlinite pipes, Red Cloud's quilled hide shirt and Crazy Horse's whetstone, are displayed in the James Cook Gallery.
More than four miles of self-guiding trails lead past fossil quarries (not currently under excavation) and a historic cabin. A covered picnic area is available to visitors. Note: Beware of rattlesnakes within the park. Collecting of fossils, rocks or plants is forbidden.
The park is open daily dawn-dusk. Visitor center and museum open daily 9-5, May 15-Sept. 30; 8-4, rest of year. Closed Jan. 1, Thanksgiving and Christmas. Free. For more information, phone (308) 668-2211.