The Cleveland-Lloyd Dinosaur Quarry once lured up to 5,000 visitors annually to a booming bone repository 13 miles from Elmo.

Those numbers could rise now that the U.S. Bureau of Land Management has completed an expansion and renovation that nearly tripled the visitor center's floor space, according to Paleontology Coordinator Michael Leschin.

In this remote tourist attraction, skulls of the long-necked Diplodocus and armor-plated Stegosaurus emerge from stone mounts on the walls. An Allosaurus skeleton - extracted largely from the Emery County quarry - turns its gaping jaws upward as if to attack.

There's also mystery to this quarry, unearthed in the late 1920s at the end of a stream bed.

Paleontologists have discovered more than 10,000 bones within a narrow layer of mudstone. What's missing is a complete skeleton.

The quarry's bones are scattered haphazardly over a quarter acre with no hint as to why, Leschin said. Normally, bones would show signs of movement by water, mud or predation. But these don't.

What's more peculiar, three quarters of the 70 dinosaurs found at the quarry are meat eaters.

"Something weird was going on here," Leschin said.

While researchers have suggested a few possibilities - a muddy bog, a contaminated water hole, a devastating flood - no one can explain the jumble of bones entirely.

But that's OK, Leschin said. It gives visitors something to chew on.

Although obscure outside the paleontology world, the Cleveland-Lloyd Dinosaur Quarry has a reputation that extends beyond the San Rafael Swell.

Its bones - mostly from the meat-eating Allosaurus - have traveled to museums in Japan, Turkey, France, Kuwait and a handful of other countries.

"This is a world-class site," Leschin said.

jstettler@sltrib.com