Ray Stanford, 74, was having lunch at the Goddard cafeteria with his wife, Sheila, June 25 when he made the discovery, The Washington Post reported.
Six years earlier, Stanford found a small triangular chunk of stone stamped with a three-toed footprint, and in June he thought there might be more there.
"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."
Stanford, who has collected about 1,400 dinosaur footprints and other fossils in his career, then found an impression nearly 14 inches wide that he believes to be from a nodosaur, which were common in Maryland about 112 million years ago.
"These guys were like four-footed tanks," Stanford said of the dinosaur that grew thick, spiky armor adorned with big "nodes."
Stanford showed the print to Johns Hopkins University expert David Weishampel, author of the book "Dinosaurs of the East Coast" and a consultant on the 1993 film "Jurassic Park," who said he thinks it's the real deal.
"Ray showed it to me, and I was overwhelmed," Weishampel said. "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."
Goddard's architect and facility manager, Alan Binstock, said he's never heard of dinosaur footprints or fossils being found at any of NASA's 13 nationwide campuses in his 20 years working for the space agency.
"I love the paradox," Stanford said. "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."
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