St. George » How to differentiate between a valuable fossilized dinosaur egg and an ordinary rock will be part of an exhibit opening Monday at the Dinosaur Discovery Site at Johnson Farm in St. George.

"Hatching the Past," examines the phases of dinosaur development through eggs, nests and embryos collected from around the world.

The public is invited to the 4 p.m. exhibit opening.

Museum coordinator Anneli Segura said the exhibit will include instructions distinguishing eggs from rocks.

She said hundreds of people have visited the museum with regular round rocks thinking they're dinosaur eggs. "But they never are," Segura said. "One guy even brought in what he thought was a fossilized dinosaur knuckle."

The 500-square-foot exhibit is being leased from Stone Co. Inc., based in Boulder, Colo.

The company assembles dinosaur exhibits of real and replicated fossils for museums worldwide.

Segura said the display is the first outside exhibit featured at the St. George museum since it opened four years ago.

She hopes it will increase visitors to the museum, which began after a discovery in 2000 by St. George physician Sheldon Johnson while he was digging on his property for a development.

The St. George site revealed a plethora of tracks from dinosaurs that once roamed the shores of Lake Dixie, which covered part of southern Utah during the early Jurassic period about 198 million years ago.

The city bought the property and enclosed part of the site within the museum.

Segura hopes this year's centennial celebration of nearby Zion National Park increases the number of visitors to the exhibit, which will also offer something new to locals.

Andrew Milner, the museum's paleontologist, said most eggs from the exhibit were discovered in northern China and are of oviraptors, a feathered dinosaur that ironically was a carnivore preferring to dine on the eggs of other dinosaurs.

The exhibit also features eggs of other creatures past and present, including one the size of a small watermelon from an extinct elephant bird that was 11 feet tall and weighed 1,000 pounds.

In addition, art work by paleo-artist Luis Rey will be displayed along with interactive exhibits for children.

Among the more unusual items will be a replica of Baby Louie, a dinosaur embryo discovered in China by Charlie Magovern, a co-founder of Stone Co.

Magovern said he discovered the rare fossil while working on dinosaur eggs from China.

"It was one of those three-in-the-morning discoveries," Magovern said. He said the St. George exhibit is among the smaller ones assembled by his company.

Currently Stone has exhibits in Detroit, Orlando, Fla., and Australia.

"I've been interested in this kind of thing for 30 years," Magovern said.

mhavnes@sltrib.com