Brett French via AP, The Billings Gazette
In this photograph taken on April 11, 2015, a quarter sits next to a three-toed dinosaur track fossilized in an ancient shoreline near Shell, Wyo. Much of the state of Wyoming was under the huge inland Sundance Sea 160 to 180 million years ago.

SHELL, Wyo. — Every time Cliff Manuel talks about the amazing dinosaur fossils that have been unearthed near his Shell, Wyo., home, his wife, Row, makes him recount the discovery of the Red Gulch Dinosaur Track Site in 1997.

"We were driving out on this back road, which was basically a four-wheel drive road, driving by this road wash and — my wife and I had probably driven past it 100 times — and my wife wanted to stop but I always said, 'No, let's go look at something more interesting,'" Cliff Manuel recounted.

"They just don't like to listen to a woman's viewpoint," Row Manuel joked.

But on the trip in 1997, Manuel's nephew Erik Kvale was along for the ride. It was Kvale who urged his uncle to pull over so they could take a closer look at the obvious ripple marks in the exposed tan rock that had been exposed by outflow from a road culvert.

Kvale, who is now a geological adviser for a national energy firm, had been taught that much of Wyoming — including the area where they were looking at the ripple marks — was under the huge inland Sundance Sea 160 million to 180 million years ago.

As they stood looking at the fossilized ripple marks in the now desert-like area west of the Bighorn Mountains, Cliff Manuel said he asked his nephew if they should be looking for tracks in the ancient mud. Kvale told him not to bother since the prevailing theory was that the area was all underwater when the ripple marks were created.

Then Kvale said, "Wait a minute, here's one right here! There's another one!" Manuel recounted.

"They were all over the place," Cliff Manuel said and chuckled. "I was down on my hands and knees getting closer, and he was running around. He said, 'They're all over the place down here!'"

The small group of discoverers, which included Fran Patton and Allen Archer, had come upon what is now considered one of the best preserved dinosaur tracksites in the world. Originally the group thought they were on private land, but after contacting the Bureau of Land Management, which conducted a survey, they found out the site was on BLM property, Cliff Manuel said.

For nearly a year the BLM kept the discovery under wraps as scientists studied the site. By looking at the age of fossilized oysters and volcanic ash found just above the rocky ripples, scientists put the age of the tracks' creation at 167 million years old — what's known as the Middle Jurassic period, the Billings Gazette reported ( ).

"It's one of the premier paleontological sites the BLM has, not only here in Wyoming, but in the country," said Brent Breithaupt, the BLM paleontologist in Wyoming.

Since its discovery, scientists have documented 125 track ways with an estimated 1,100 different individuals leaving marks in what was once the beach of the ancient sea. The track sizes range from 3 to 8 inches long. All were made by three-toed dinosaurs that scientists speculate were probably meat eaters like theropods — ancestors to the Tyrannosaurus rex — which walked on their two hind legs. It's estimated by the varied depth of the footprints that the dinosaurs weighed up to 400 pounds.

One interpretation of the site is that it was a family group of adult and juvenile dinosaurs all moving at one time, Breithaupt said.

"It exhibits some level of social activity, which we don't think of for dinosaurs," he said.

Based on an analysis of the ripple marks, it appears that all of the dinosaurs were walking south to southwest toward what would have been deeper water, instead of along the edge of an ancient shoreline. The type of mud, which contained ground-up seashells that created lime, acted almost like modern cement to preserve the footprints. Scientists call it the Goldilocks effect, since all of the conditions have to be just right for the footprints to be preserved.

In the wake of the discovery, the Manuels created a summer GeoScience Adventures camp in 2000 that guides people around the Shell area, with some expeditions led by geologists like Kvale and other experts.

Now 84 years old, Cliff Manuel credits the adventurous hikes, as well as the scientists they attract, with keeping him in good health.

Row Manuel, who grew up on a dude ranch in Shell, Wyo., has been around geologists and paleontologists since she was a young girl. Her parents, who had settled in Wyoming after moving from the East, knew famed fossil hunter Barnum Brown. Brown worked for the American Museum of Natural History in New York, traveling around the world in search of fossils — including his excavation at what's known as the Howe Dinosaur Quarry near Shell, Wyo., where thousands of sauropod bones were discovered in the 1930s.

"I knew about fossils when I was young, but I didn't care about them," Row Manuel said. "We had many geologists stay on the ranch, but to me they were just another geologist."

It wasn't until the couple retired back to her old hometown that Row Manuel said she got "bitten by the fossil bug." In 1994, she found the fossil of an ancient marine reptile, an ichthyosaur, "in the backyard."

"I'm finding it more fun now that I'm an adult," Row Manuel said. "I kind of enjoy hiking the hills now."

Breithaupt said the tracksite was probably exposed for decades before it was reported to the BLM.

"If you think about that, there are a lot of sites yet to be discovered in Wyoming, just out there in the backcountry that people haven't recognized yet," he said.

Row Manuel would agree. She especially enjoys examining anthills in the desert badlands of the Bighorn Basin.

"My wife has trained ants to collect fossils for her," Cliff Manuel joked.

The ants unearth what Row Manuel calls micro fossils of star-shaped crinoids, ancient marine animals resembling lillies. She said when she and Cliff give tours of the Red Gulch Dinosaur Tracksite, visitors are often more interested in the anthills because "they get to find their own fossils."

"It's more fascinating than their old dinosaur footprints," she said.

Information from: The Billings (Mont.) Gazette, ,