Morrison, Colo. ? Dinosaurs tramped on what was once a beach in Colorado, leaving tracks that have remained remarkably well preserved on a small slope in the mountains southwest of Denver.

The tracks of the three-toed dinosaurs resemble giant chicken prints and have endured the elements for millions of years but are eroding and could soon be gone, according to Friends of Dinosaur Ridge, the nonprofit group that manages the site.

But there’s no easy fix to the problem. The group proposed building a canopy over the tracks to protect them, but it’s an idea that county officials say will diminish the majestic views of Colorado’s Front Range.

“The plan that they came up with includes structures and it just doesn’t work,” said Kathryn Heider, a spokeswoman for Jefferson County, which owns the land where the tracks are located 15 miles from Denver. “It doesn’t mean we don’t want to preserve the footprints. It just means we don’t want structures on the backdrop.”

Rain, snow and freeze-thaw cycles have caused slabs of shale to crack and break off from the slope where the tracks and micro layers are eroding, said Joe Tempel, executive director of Friends of Dinosaur Ridge.

“We project that we have between 10 or 15 years to protect them or they’re going to be gone,” Tempel said.

Discovered in 1937 during road construction, they show about 300 individual tracks from three types of dinosaurs, including an Iguanodon that walked on four feet. The site spans about three or four car lengths and also has tracks that were made by a crocodile. The tracks were made more than 100 million years ago, when the now mountainous area was the coast off an ancient seaway.

Friends of Dinosaur Ridge has archives of photos spanning decades that show tracks that have since disappeared.