A stunning imprint of a hatchling dinosaur found by a local fossil enthusiast is helping to fill a missing chapter of pre-history.

For 150 years, paleontologists have found scattered evidence of dinosaurs living in the region 110 million years ago.

But until Ray Stanford’s discovery, they had never seen a near-complete outline of a baby dinosaur known as a nodosaur.

Low-slung and heavily armored, nodosaurs — a group similar to the better-known ankylosaurus — sometimes grew to be 20 feet long. The body of the dinosaur Stanford found, in contrast, measures just five inches.

The youngster apparently died on its back, leaving an imprint of its head and most of its body.

It’s the first hatchling nodosaur ever found, paleontologists say.

“Now we can learn about the development of limbs and the development of skulls early on in a dinosaur’s life,” said David Weishampel, a dinosaur expert at Johns Hopkins University who consulted on the film Jurassic Park. “The very small size also reveals that there was a nearby nesting area or rookery, since it couldn’t have wandered far from where it hatched.”

When Stanford pulled a small slab of rock out of a creek bed near his College Park home in 1997, he thought it might hold a footprint — and he would know, as he’s collected hundreds of dinosaur tracks from the region.

“We put it up above the stove where the sun hit it and we got some unusual shadows,” said Stanford, 73. “And here I saw ribs sticking out. I took a brush and brushed it out. I said, ‘We’ve got a small dinosaur here.’ ”

Stanford noticed a distinctive cross-hatched pattern on the head. A check of a reference book told him he had a nodosaur on his hands. Stanford then called Weishampel, and the pair collaborated on a description of the fossil published this week in the Journal of Paleontology.

Stanford dubbed the find Propanoplosaurus marylandicus.

“We didn’t know much about hatchling nodosaurus at all prior to this discovery,” said Weishampel. “And this is certainly enough to motivate more searches for dinosaurs in Maryland, along with more analysis of Maryland dinosaurs.”

Stanford donated the fossil to the Smithsonian Institution’s National Museum of Natural History, where it is a centerpiece of the “Dinosaurs in Our Backyard” exhibit.

The donation delighted Matthew Cerrano, the museum’s dinosaur curator. “I’ve never quite seen a fossil preserved like that,” he said.