They're big, bad, old as boots and craggy as the Rolling Stones. All hog the spotlight like Mick Jagger. And each one looks as indestructible as Keith Richards.

The stars of "Walking with Dinosaurs -- The Live Experience" bring the tar pit to the mosh pit.

The live spectacle, starring 15 full-size animatronic dinosaurs that snap, snarl and strut their stuff, is billed as educational. But a rock-concert vibe dominates both sides of the footlights.

During a recent performance, puppeteer Graeme Haddon couldn't hear his Tyrannosaurus Rex's roars "over the screams," he said.

And just wait until the finale. Spoiler alert: Mama T. rex is one mean mother. "The crowds go berserk," resident director Cameron Wenn said. "They just love it."

Based on the BBC series "Walking with Dinosaurs," the $20 million spectacle -- based at United Center through Aug. 17 -- debuted last year in Australia.

The brainchild of artistic director William May, the show was designed to condense the six-part series into a 90-minute-plus-intermission arena show starring mechanical monsters. As the dino-bots lumber, feed and lock horns, an actor in a safari suit narrates each one's history and likely habits.

As a pack of divas would expect, no expense was spared for their close-ups. The lizards rate their own symphonic score and enough special effects to turn the Glimmer Twins pea-green. For example, lights and projected images help whisk audiences through time and climatic changes linked to the species' demise. Actors James Robert and Jonathan Bliss take turns playing paleontologist Huxley.

Narrowing the dino-cast to 10 species was a snap, said Wenn, who has worked with the show since its inception. "There were favorites that everyone wants to see, like the Stegosaurus and T. rex. Everyone knows those guys," he said.

The rest of the gang was tapped to represent the three periods of the dinosaurs' 200-million year reign. The Plateosaurus and Liliensternus made the cut from the Triassic era, the Allosaurus from the Jurassic era. The horned Torosaurus and Utahraptors are refugees from the Cretaceous years. The long-necked Brachiosaursus was added for visual oomph. He stands 36 feet tall and measures 56 feet long.

HIGH-TECH DIVAS

The brutes ain't sock puppets. It took a team of 50 to build the giant carnivores and herbivores, all which owe debts to the computer hardware and software developed for the BBC series.

Sony Tilders, a lead animatronic engineer for Jim Henson's Creature Workshop, hatched a plan to make the robo-puppets look as real as their life-sized counterparts. Thanks to their hydraulic systems, the 10 larger dinosaurs already were bulky, weighing more than a ton apiece. But he buffed them up by stretching "muscle bags" of mesh fabric filled with polystyrene balls across their moving parts.

The bags "contract and stretch in the same manner that muscle, fat and skin does on real creatures," Tilders said in a statement. Designers and artists teamed up for each beast's hand-painted "skin."

The combination of science, sci-fi fantasy and escapism created a roar. Ticket sales were mammoth Down Under and the dino-rama was earmarked for a 60-city, two-year North American tour. Over 1 million people have gaped at the walking, snorting beasties since spring. The New York Times hailed the dinosaurs for making "a thundering comeback after 65 million years."

PAMPERED PREDATORS

Like rock stars, the headliners require a huge entourage. The giant puppets travel from gig to gig via 27 53-foot-long semis. A production manager who worked for the Stones helps oversee 45 crew members who include engineers, lighting and sound technicians, riggers and carpenters.

The stars also have personal assistants. A trio of staffers are assigned to each dinosaur per show. One, hidden in a go-kart-like vehicle inside the dinosaur, drives it like a parade float. The other two are puppeteers who use "voodoo rigs" to control the beast's head and tail, and jaws, eyeblinks and roars respectively.

A voodoo rig is "a strange contraption of aluminum springs and wire," Haddon explained. As he manipulates the rig, each Wii-like motion transmits radio waves that are intercepted by hydraulic cylinders within the puppet. The puppet then replicates the movement. "It's like a giant toy. It's fun," Haddon said.

The show's as orchestrated and choregraphed as any rock extravanganza. The puppeteers, wearing headsets and black garb, stand in a row near the sound and light boards so they can watch and hit their marks. Haddon and his mates have dubbed their space the "Voodoo Lounge," a tip of the hat to the Stones' 1994 album and tour.

OCCUPATIONAL HAZARDS

Pulling the right strings, so to speak, is a delicate art. When an arena is packed with massive monsters, the odd collision may ensue. The dinosaurs can take the lumps, but the costumed actors who play five smaller dinosaurs log the occasional bruise.

William Landsman, who plays Baby T. rex,, once tripped over the tail of a 34-foot long Ankylosaurus. Fog machines were rolling and it was hard to see, he explained.

"Yeah, if you take a fall, you get bumped around," he said cheerfully.

For the record, it is intimidating to be a 5-foot 10 actor in a 7-foot-tall costume running amok -- Baby T. rex is mischievous -- surrounded by ancient giants.

"They're huge," he said. "It's kind of scary the first time you're out there with them. You know there's someone alive driving (the puppet), but when they come at you, you give them a wide berth. ... You're looking up at them and the size comparison, well, they're gargantuan. And they're snapping and trying to put a horn through you."