The largest dinosaur ever unveiled in Canada -- the Royal Ontario Museum's recently discovered Barosaurus -- will be unveiled this weekend after spending more than 40 years in the museum's basement.

Dr. David Evans, associate curator in vertebrate palaeontology at the ROM, told Canada AM on Wednesday that the rare sauropod skeleton was long forgotten before he discovered it last year.

Nicknamed Gordo, the Barosaurus will complete the dinosaur specimens in the museum's new James and Louise Temerty Galleries of the Age of Dinosaurs, located in the recently opened Michael Lee-Chin Crystal.

The skeleton dates back to the late Jurassic age, making Gordo about 150 million-years-old. Barosaurus, meaning heavy lizard, is a member of the subgroup Sauropoda. Sauropods are marked by their large size, long necks and tails, a four-legged stance and herbivorous diet.

Evans said the discovery was an incredibly lucky find.

"We were just looking for a sauropod to round out our dinosaur story here in the new gallery," he said.

"We had a Tyrannosaurus Rex and a Stegosaurus and we have a Triceratops -- and the only dinosaur icon we were missing was one of these giant sauropod dinosaurs."

Before discovering Gordo, Evans and his colleagues mulled over a number of alternatives.

"We didn't think we had one here, so I started looking elsewhere," he said.

The museum received a tip about a Barosaurus skeleton recently discovered in the U.S. that could work for the ROM's new exhibit.

"At the very end of September, I was flying out to Wyoming to size up this find in the ground," Evans said.

"I was going through a recently published paper that happened to be on Barosaurus and came across a really strange reference that caught my eye that I really didn't expect to be there."

The paper, by expert Jack McIntosh, referenced "these great elongate cervical vertebrae" of a Barosaurus that were part of a skeleton already in Toronto.

"I knew that that had to be in our very own collection," Evans said.

No one from the ROM recognized the reference until a miscellany of disjointed bones was discovered scattered in various locations in the museum's collections room.

The bones were bought from Pittsburgh's Carnegie Museum of Natural History in 1962 by ROM curator Gordon "Gordo" Edmunds. After Edmunds retired and later died, the bones were forgotten about.

Gordo is one of two Barosaurus skeletal displays in the world, but is rare because it "is the only one that has the real fossil bones incorporated into a skeleton that's in a life-like pose," Evans said.

The new galleries, which are the first permanent galleries in the new addition, will present more than 750 specimens including about 50 dinosaur specimens, of which 20 are complete or nearly complete skeletons.

The ROM's Dino Family Weekend will begin on Dec. 15 with the official opening of the new galleries. The Barosaurus skeleton will stretch along the east window of the Crystal offering visitors a glimpse at the rare find even before entering the museum.