Retired schoolteacher Pat Weidknecht hunched over in the sun, plucking small bits of old bone from a rocky patch of desert at the valley's northwestern edge.
The ground was littered with the fossilized fragments of mammoths, horses and camels, so Weidknecht spent hours on her hands and knees, gathering up the pieces like an ice age crime scene investigator.
Some of the splintered bones were as big as a hand. Most were smaller than a finger and resembled chunks of plastic pipe or plain old rocks.
Weidknecht picked them up one by one and dropped them in a plastic sandwich bag.
The work was hot, tedious and sometimes uncomfortable, and she couldn't have been happier about it.
"The fact that I held something in my hand that is anywhere from 10,000 to 60,000 or 70,000 years old - something that was living, something that used to roam out here - that's cool. That's just cool," she said as she kneeled on a throw pillow at the edge of a dig site in the Upper Las Vegas Wash.
Weidknecht is part of a small army of volunteers recruited to keep an eye on the fossil-rich swath of federal land where researchers are trying to unlock the mysteries of climate change and mass extinction at the end of the last ice age. More than 75 valley residents have been trained as site stewards by the U.S. Bureau of Land Management and its research partners from the San Bernardino County Museum in California.
Each steward is assigned a 1-square-mile area to check on at least four times a year for signs of human disturbance or new evidence of fossils emerging from the ground at previous dig sites, a process known as "cyclic prospecting."
The job is part security guard, part "citizen scientist," according to geologist and paleontologist Kathleen Springer, who leads the San Bernardino County Museum's work in the Upper Las Vegas Wash.
"There's potential for stuff to be eroding out of here for thousands of years," Springer said. Without the site stewards, it would be almost impossible for researchers like her to check and recheck roughly 500 fossil sites scattered across more than 13,000 acres, she said.
As a reward for the stewards, Springer and company took them along on a dig early this month. The event was held with the 50th anniversary of the "Big Dig" at Tule Springs, a 1962 operation that featured the first large-scale use of radiocarbon dating.
Over three days, the site stewards helped collect fossils at three areas near the wash.
One site yielded so much mammoth bone scattered at the surface that the team didn't have time to dig down to see what might be hiding underneath. The two other sites offered a few more mammoth bones and the fossilized remains of other long-extinct mammals.
A few feet from where Weidknecht was kneeling in the dirt, they collected the jawbones of two ice age horses and several large rib bones lined up roughly the way they would have been inside the mammoth that once carried them.
They also recovered the specimen that brought the site to Springer's attention to begin with: a football-sized mammoth tooth eroding in plain sight at the base of a creosote bush.
For Weidknecht, it was an eye-opening look at a part of the valley she was familiar with for other reasons. When she taught history and government classes at Shadow Ridge High School, she also coached the cross country team. She used to send her runners out to practice in the chalky hills now proposed for federal protection as Tule Springs Fossil Beds National Monument.
"It's neat to be able to come out here and see what the scientists are actually finding," she said.
Bills establishing the 22,650-acre national monument were introduced in the House and Senate in late June, but neither measure has advanced since then. There is still a slim chance the lands bill could win approval during the current lame-duck session of Congress, but most likely it will be left for dead until next year.
In the meantime, researchers continue to collect bones and make surprising discoveries in the Upper Las Vegas Wash.
"As we say, our science is only as good as our last field season," said Eric Scott, who serves as curator of paleontology for the San Bernardino County Museum and drives around the wash in an SUV with plates that read "FOSSILS."
Springer said the research team hopes to start publishing its findings next year in a series of papers that should serve to "elevate the Las Vegas formation to this glorious thing we now know it to be."
"There's a quarter of a million years of time recorded here, and there are fossils almost all the way through," she said.
In one of the most exciting discoveries, geologist Craig Manker has been able to establish a fine chronology of climate events in the wetlands that once existed here. Those abrupt changes appear to coincide almost exactly with broader climate events identified using ice cores from Greenland, Springer said.
Ultimately, the more we know about ancient climate change, the better chance we have of understanding what is happening now, Springer said. "The past is prologue."
Researchers also are using the thousands of bones they have found from a wide range of time periods to test various ideas about what caused the mass extinction of the large ice age mammals about 10,000 years ago.
Some blame climate change. Others suspect the animals were killed off by a disease , hunting by early humans or even a comet colliding with the planet.
"That's a subject still up for debate," said Scott, who has his own hypothesis involving giant herds of bison. "This area is a perfect lab for testing all of that."
There is certainly no shortage of research materials.
At one site Scott called the "super quarry," the San Bernardino County team used hand trowels and paintbrushes to untangle a pile of 500 individual bones packed into a hole smaller than a UPS truck. The haul included five tusks from at least three mammoths.
Scott said the spot didn't look like much at first - just a small scattering of bone at the surface - but after a year of digging, it ranked as the biggest site that has ever been found in a wash littered with big sites.
Today, all that is left is the hole they dug, which has since been tagged with graffiti on one 8-foot wall.
Springer said it's a perfect illustration of the important role site stewards play in an area filled with scientific treasures but heavily scarred by ATV tracks and illegal trash dumps.
It speaks to why the area deserves more federal protection and why it needs people like Weidknecht looking out for it until that happens.
"Las Vegas is built on this stuff," Springer said of the fossil-rich earth in which her team will continue to work until at least 2014.
"This is the last bastion of this deposit left. After this, it's gone."
Contact reporter Henry Brean at email@example.com or 702-383-0350.