Three-year-old David Shiffler had just seen a movie about dinosaurs and couldn't stop talking about them, so when he told his father he had dug up part of a dinosaur egg, all he got was a shrug.

"He said, `Yeah, right,' " David said Thursday as he played in a sandbox while museum scientists showed off the 150-million-year-old discovery the boy unwittingly made last October.Scientists labeled David's find - made in the sandy Rio Puerco valley west of Albuquerque - a major discovery because it's one of only a dozen ever found from the Jurassic Era.

Spencer Lucas, a scientist at the New Mexico Museum of Natural History and Science, said David is likely the youngest person to ever make such a find.

Lucas said the 1-square-inch piece of fossilized egg could help paleontologists piece together more about life in an era when flying reptiles cruised the skies and huge, vegetarian dinosaurs roamed the land.

David's father, Don Shiffler, said he and his son were coming home to Albuquerque from a camping trip in the Mount Taylor area, about 80 miles away. They took a potty break near Rio Puerco, and David started using a toy backhoe to go digging through the dirt.

The family had just watched "The Land Before Time," an animated kid's movie about a little dinosaur who goes searching for the rest of his family after his mother is killed by a tyrannosaurus rex.

So, Don Shiffler said, "he was fascinated with dinosaurs. Everything he picked up that day was a dinosaur egg."

David insisted he had several more at home.

"We've got thousands of them," he said.

If so, Lucas said he'd love to see them. He said David's discovery was key because it furthers the theory that all dinosaurs laid eggs.

It could prove dinosaur eggs from that era were hard-shelled, advancing the theory that modern birds are descendants of dino-saurs.

Museum scientists waited to tell the public about the discovery until they could go to the site and see if there were other signs of dinosaurs. Lucas said a search of the area turned up nothing.

Lucas said plenty of egg fragments exist from 70 million to 100 million years ago. But he said some scientists believed there was a dearth of the older egg fragments because the eggs had a leathery texture and thus, couldn't be fossilized. Lucas said this discovery could help debunk that hypothesis.

The fragment is a grayish piece of shell with black bumps on the outside and a smooth, silvery texture on the inside.

Don Shiffler said his son's find intrigued him enough to bring it into the museum, along with several pieces of relatively unimportant fossilized bone.

"Luckily, David is the kind of kid who likes to pick up strange objects," Lucas said. "There aren't nearly enough paleontologists to pick up every fossil that's out there. So we rely heavily on the public, whatever age, to alert us to discoveries."