Dino fever grips Chicago

Sue is set to become a major draw for the Field Museum

Thousands of people came to gawk at the world's largest, most complete and best-preserved Tyrannosaurus rex skeleton when it finally went on display in Chicago, US, on Wednesday.

The crowd in the main exhibit hall at the Field Museum broke into applause as a screen fell and the creature emerged in a swirl of smoke, music and spotlights.

"She's really big and she's really cool. What else can you say?" said Sarah Bosley, a fifth-grader from Castle Rock, Colorado.

The monster specimen is called Sue, after the fossil hunter Sue Hendrickson who discovered it in 1990.

The dinosaur, unearthed in South Dakota's Black Hills, cost the natural history museum $8.36m at an auction that had been delayed for years by a drawn-out legal battle that ended with Hendrickson's partner in jail.

Scientific surprises

To cover the cost of the 67-million-year-old carnivore, the Field has taken on two major corporate partners in McDonald's and Disney.

Face of a monster: Sculptor Brian Cooley made this impression of Sue Field Museum

The two organisations share exclusive rights to casts of Sue's bones; the museum keeps the real ones.

The Field used the unveiling to announce that the fossilised bones had provided some scientific surprises about the ferocious species during the nearly three years it took to reassemble the creature bone-by-bone.

One was the presence of a wishbone, the first ever found in a T.rex and additional proof for those who believe dinosaurs are related to birds. The wishbone is a structure unique to fowl.

In addition, the fossil is the first of a T.rex ever found with an ear drum bone called a stapes - also found in birds - that helps transmit sound to the inner ear.

Top speed

"This delicate ear bone is almost never preserved in dinosaur fossils," said John Flynn, head of the museum's geology department. "Its presence allows us to better understand the evolution of ear bones and hearing in dinosaurs and in birds."

Sue Hendrickson watches restorers as they make a cast of the lower jaw of the dinosaur

Experts said they had determined that Sue probably walked at a relatively slow gait - about 9.6 km/h (6 mph) - with a top speed of perhaps 24.1 km/h (15 mph), a pace slower than some scientists had previously thought.

The animal also had a keen sense of smell, thanks to huge olfactory lobes, leading experts to believe it may have moved through life "nose first," but shedding no light on whether it was a predator of a scavenger.

Sue's one tonne skull, was too heavy to mount with the rest of the skeleton, and is now displayed in a case nearby. A lightweight cast has replaced the real thing on the skeleton.

Fewer than 25 such carnivores have ever been unearthed, and being 85-90% complete, Sue is the most comprehensive T. rex dug up so far.

Longest tooth

"She" - palaeontologists are not really sure of the animal's sex - has one of the only two T. rex arms ever to be discovered.

Sue can also boast the longest tooth yet found for a T. rex, measuring 30 centimetres from root to tip.

Visitors to the Field can view animated scans of the skull, generated by computer, and touch a variety of casts of Sue's bones, including a rib, forelimb and tooth.

Video clips recap the story from Sue's discovery to "her" arrival at the museum.

A time-lapse video shows the mounting of Sue's colossal skeleton, and a webcam will allow surfers around the world to see the dinosaur.

"She's really big and she's really cool"