WASHINGTON — Eons before man dreamed of exploring the heavens, dinosaur tracker Ray Stanford is convinced, a low-slung armored beast roamed what is now a NASA campus in Greenbelt, Md., stamping a huge footprint that went unnoticed until he spied it this summer.

A scalloped mini-crater with four pointy toe prints pressed into ruddy rock, the putative dinosaur track juts out from a scruffy slope at NASA's Goddard Space Flight Center, home to 7,000 scientists, engineers and other workers with their eyes firmly turned skyward.

Maryland's signature dinosaur, an armored browser known as a nodosaur, made the track with its back left foot 112 million years, Stanford said as he led an entourage of NASA officials to the print Friday morning.

Sticking out of the grass in plain view, the elephant-foot-size impression — nearly 14 inches wide — elicited gasps. "Unbelievable!" said a NASA photographer. Someone else said, "Oh, my!"

NASA officials said they accept the discovery for now as an authentic dinosaur footprint. They are moving to call in experts to confirm the find and search the area for other dinosaur calling cards.

Last week, Stanford showed the print to noted Johns Hopkins University expert David Weishampel, author of the book "Dinosaurs of the East Coast" and a consultant on the 1993 film "Jurassic Park."

Weishampel said that the track, pressed into the bedrock undergirding the campus, is real.

"Ray showed it to me, and I was overwhelmed," Weishampel said in a phone interview. "As a scientist, I'm skeptical of things like this. But it has all the detail you want. It's got toe prints and sort of a heel print that's starting to erode away."

Added Weishampel: "It looks like a nodosaur."

On Friday morning, Stanford pulled out a paintbrush and dabbed dirt from around the edges of the print, highlighting where he says four sharp toes once pressed into mud that eventually hardened into stone.

"These guys were like four-footed tanks," Stanford said of the beast that left the track. Nodosaurs grew thick, spiky armor knobbed with big "nodes," the origin of their name. They browsed vegetation and hunkered low to survive toothy attacks.

Stanford speculated that the nodosaur was running when it laid down the presumed track, possibly fleeing a predator.

"I love the paradox," said Stanford, 74. "Space scientists walk along here, and they're walking where this big, bungling, heavy-armored dinosaur walked maybe 110, 112 million years ago. It's just so poetic."

A Goddard official, Alan Binstock, said the agency considers the footprint and its location "sensitive but unclassified."

He grew nervous as Stanford set a small plastic nodosaur inside the print for a photograph. "Maybe put the toy dinosaur away so it isn't so obvious to people," said Binstock, scanning for passers-by.

As Goddard's architect and facility manager, Binstock said he would quickly move to protect the footprint. He proposed temporarily covering it and lamented that it looked as if a "big gang mower" had recently chipped its edges.

In his 20 years at NASA, Binstock said, he's never heard of dinosaur footprints or fossils being found at any of the space agency's 13 nationwide campuses.

Jennifer Groman, NASA's federal preservation officer, who typically safeguards spacesuits, satellites and other man-made detritus of the space-age, viewed the imprint Friday.

"It's not something I want to make a tourist attraction at this point," she said. "We don't want people barreling down there with shovels. We can't have anyone pick it up and take it off property."

Groman added that "ultimately, we want people to be able to see it, because it's very exciting." An interpretation station could be built at the site, Groman said.

Because the impression is on federal land, three laws may apply: the Antiquities Act, the Archaeological Resources Protection Act and the Paleontological Resources Preservation Act.

Groman and Binstock asked The Washington Post not to reveal the track's location on the 1,270-acre Goddard campus.

Nodosaurs were not known to roam what is now Maryland until Stanford uncovered a fossilized baby nodosaur near the University of Maryland campus. Stanford and two academic colleagues from Johns Hopkins dubbed the species Propanoplosaurus marylandicus in a peer-reviewed scientific paper published in September in the Journal of Paleontology.

Stanford donated that fossil — the first hatchling nodosaur fossil found anywhere — to the Smithsonian's National Museum of Natural History, where it sits under lights in the "Dinosaurs in our Backyard" display.

That doomed baby nodosaur measures just six inches long, but the relative that made the Goddard footprint was "huge," said Stanford — 15 to 20 feet long. Like all dinosaur tracks in the region, the one at Goddard probably hails from the early Cretaceous period, about 112 million years ago, he said.

Stanford has earned a reputation as a footprint-finder extraordinaire. Since 1994, he has collected about 1,400 dinosaur footprints and other fossils from the streambeds of Prince George's County, adding to the scientific record a menagerie of at least 20 new Maryland dinosaurs. In contrast, the bones of just three or four species of Maryland dinosaurs have been found, experts say.

With piles of dinosaur tracks filling his living room, Stanford's home in College Park, Md., holds "the best collection of footprints we have from early Cretaceous era of the East Coast," Weishampel said. "Ray has unleashed upon us a whole new, and quite diverse, fauna. He's found tracks for animals we don't have bones for yet."

Stanford's most recent discovery was made June 25. He and his wife, Sheila, were having lunch at the Goddard cafeteria when Ray got one of his "hunches." If he returned to a spot where six years before he had found a small triangular chunk of stone stamped with a scrawny three-toed footprint — likely from a two-legged meat-eating theropod, Stanford said — there might be more to find.

"I drove by and said, 'There's something sticking out of the ground there,' " he said. "It's a matter of knowing what to look for."

As word of the find filtered out across the Goddard campus, incredulous reactions ensued.

Told of the apparent discovery, Piers Sellers, a Goddard scientist and former astronaut, said with bemused surprise: "I don't believe it. We have no exposed rock anywhere on campus."

Even as NASA's Groman viewed the big nodosaur print, she picked up a flat, hand-size piece of yellow stone from nearby.

Groman showed it to Stanford, who grew even more animated.

"That's from an iguanodon," he said, pointing to three rounded, fat toe prints. Iguanodons were bipedal plant-chewers.

Within 20 minutes, the Stanfords and two NASA employees picked up three more small track-tredded rocks.

Stanford then swept his arm across Goddard's asphalt parking lots and square brick government buildings and the white, 100-foot-tall Delta rocket jutting above the trees in the distance. "This must have been a nodosaur's paradise," he said. "Imagine all these nesting dinosaurs living in here. There have got to be dinosaur tracks all over this place."