The eroded formations at Toadstool Geological Park expose fossil shells, bones and tracks of ancient animals.
In an ironic twist of geography, Colorado, a state known for the snow-capped Rocky Mountains, is flat as a pancake on its eastern side, while adjacent western Nebraska has scenic hills, cliffs, buttes and badlands. Just looking at the eroded spires, chiseled hills and mushroom-shaped formations, you know this ancient land is full of surprises.
Many of the surprises hidden in this rugged landscape are exposed along the 160-mile Fossil Freeway, which runs along Highways 29/71 between Scottsbluff in the panhandle of western Nebraska and Hot Springs in South Dakota. The freeway connects a series of amazing discoveries that spans the time from the formation of the Rockies millions of years ago to the paleo-Indians who roamed the Great Plains 10,000 years ago. Erosion has exposed beds with thousands of jumbled bones, skeletons and artifacts that show us how radically the landscape and the creatures that lived here have changed. In fact, you can see fossils still in place in the ground where they were discovered.
When the Rockies began inching toward the sky 80 million years ago, the moisture streaming inland from the Pacific Ocean could no longer reach the center of the continent. As the climate dried, the vast forests turned to Serengeti-like grasslands with herds of pony-rhinos, gazelle-camels, long-necked horses, voracious bear-dogs and saber-toothed cats. Great droughts forced animals to congregate around the remaining waterholes where they died en masse of dehydration and starvation. Layers of ash from mountain volcanoes and wind-blown sand eventually covered the prairies with hundreds of feet of sediment.
Eons later, mammoths and giant bison dominated the plains, along with a new predator: paleo-Indian hunters. Much later, the Sioux, Arapaho and Cheyenne stalked vast herds of the smaller American bison. Now a cattle culture dominates the mixed-grass prairies, but in some places, ancient bones litter the ground like autumn leaves. They reveal a world filled with strange creatures unlike any you can probably imagine.
Bonebeds and Miocene Monsters
At Agate Fossil Beds National Monument, on Highway 29 south of Harrison, Nebraska, the Niobrara River meanders across rolling plains. The stream creates a life-giving source of water surrounded by endless prairie, much like the wetlands that existed 19 million years ago. Here, it’s easy to imagine a savanna teeming with thousands of grazing animals as well as stealthy predators.
Two hat-shaped hills rise a short distance from the visitor center and museum. It was in those hills that in the 1880s rancher James Cook discovered a two-foot-thick layer of exposed bones. Major Eastern universities flocked to excavate the site, one of the largest and most diverse bonebeds ever discovered.
Visitor Center at Agate Fossil Beds National Monument
Inside the visitor center, a film explains the animals and theories of the massive die-off that formed the bonebed. Reconstructed skeletons posed in front of a life-sized diorama painted on the wall illustrate how the creatures looked as they gathered around the disappearing water holes.
“Archaeologists found more than 30 species of extinct mammals. Most of the bones came from three species: a small rhino, a horse-headed grazing animal with long legs, and a six-foot-tall pig-like scavenger with bone-crushing teeth,” explains ranger Fred MacVaugh. “Bones from here are in museum collections around the world.”
Skeleton displayed at Agate Fossil Beds National Monument Visitors Center
A two-mile loop trail leads around the small hills, still packed with countless bones, and past two canvas teepees representing the ones made from bison hides by the Sioux in the 1800s. Though empty now, the teepees would have had bison skins covering the floor, thick bison pelts for sleeping, and a central firepit for warmth and cooking.
Teepees displayed at Agate Fossil Beds National Monument
Rancher Cook had often invited Sioux Chief Red Cloud from the nearby reservation to visit his old hunting grounds here. Over the years, the visiting Indians gave the rancher numerous gifts of exquisitely beaded shirts and jackets, bows, war clubs, and a painted bison hide depicting Custer’s Last Stand, all now exhibited in the Cook Gallery Museum in the visitor center.
Mystery Bones and Toadstool Moonscapes
The Hudson-Meng Bonebed, 17 miles north of Crawford off Highway 71 in the Oglala National Grassland, exhibits a tangled mass with thousands of giant bison bones, the world’s largest collection of ancient bison bones ever discovered. Rancher Albert Meng unearthed the bonebed in the 1950s while excavating a stock pond. The piles of “sheep” bones turned out to be from about 600 Bison antiquus killed some 10,000 years ago.
The Hudson-Meng Bonebed is enclosed for protection.
“At first, paleontologists thought this was a classic bison jump where hunters drove herds over a cliff,” says ranger Alex Miller. “But look around—no cliffs here. A theory in the 1990s suggested a massive natural disaster, but recent analysis revealed the bones were deposited over a 600-year period, and 90 percent were females and juveniles either 6 months or 18 months old. So the best guess now is this was a late-fall hunting site for countless generations. But with so many unanswered questions, it’s an ongoing mystery.”
A trail leads from the parking area down a slight hill and around Meng’s pond to a metal pavilion covering the bonebed. Exhibits show stone spear points that were found embedded in the bones and describe the giant bison that once roamed the prairies. A walkway circles the exposed dig, still being studied by various universities.
Thousands of bones of more than 600 extinct giant bison are jumbled together at the Hudson-Meng Bonebed.
After touring the exhibit, I hike a three-mile trail over rolling grasslands little changed since hunters with spears stalked giant bison 10,000 years ago. Yuccas, pink penstemons and prickly pear cacti dot the green hills. The grassy path enters Toadstool Geological Park and drops into a labyrinth of deep gullies. For two hours, I explore winding slot canyons and discover bone fragments, fossil shells and even a trackway made by ancient pony-rhinos. Near the park’s picnic area and campgrounds, wind and water erosion have carved the soft strata into a fairyland of giant free-standing toadstool formations.
The Mammoth Site of Hot Springs, South Dakota, 30 miles north on Highway 71, preserves a massive bonebed in a 26,000-year-old sinkhole. Archaeologists have identified the remains of 61 mammoths as well as short-faced bears, camels, llamas and birds. A climate-controlled exhibit hall covers the exposed bonebed, and a museum exhibits full-sized mammoth replicas. I follow an excited school group on the walkway around the partially excavated dig where skulls and bones still in place can be viewed up close.
In the summer, the Mammoth Site offers Jr. Paleontology programs for children ages 4 to 12. Four times daily, kids can get their hands dirty in the dig box searching for replica mammoth and short-faced bear bones.
Two other museums on the Fossil Freeway display replicas of animals excavated in the area. Besides pioneer and Indian history, the Trailside Museum of Natural History at Fort Robinson State Park in Crawford, Nebraska, displays a full-sized mammoth as well as the fossil remains of two mammoths with tusks locked in deadly combat and 18 other extinct animals. At the visitor center at the Wildcat Hills State Recreation Area and Nature Center south of Scottsbluff, Nebraska, you can see a pair of saber-toothed cats from 25 million years ago found in a death struggle.
Like a half-open window, the bonebeds and badlands in the six parks and preserves along the Fossil Freeway provide a glimpse into the mysterious past when long-extinct animals dominated a vastly different world.
The Niobrara River creates a prairie wetland much like the one that attracted animals whose bones lie in the distant hill of the Agate Fossil Beds wetlands.
If You Go
For a map and list of attractions on the Fossil Freeway, visit fossilfreeway.net.
This article originally appeared in the July/August 2018 issue of AAA World.