A 24-metre-long barosaurus nicknamed Gordo leans out over a Toronto street as the centrepiece of the Royal Ontario Museum's newly renovated dinosaur galleries.

The dinosaur galleries, one of the museum's most popular attractions, and the gallery of the Age of Mammals will reopen to the public Saturday.

A barosaurus nicknamed Gordo, assembled at the Royal Ontario Museum, is 24 metres long.
(CBC)

Gordo, a sauropod or "long-necked" dinosaur that had been forgotten in the ROM storage room, is the largest dinosaur ever to go on display in Canada and the most complete barosaurus skeleton displayed anywhere in the world.

His re-creation was the work of Peter May, a former ROM employee and aspiring sculptor who now is president of Research Casting International in Trenton, Ont., a company that builds dinosaurs.

"I was going to be a sculptor. It's very similar. We're building things, but I don't have to imagine them — they're there," May told CBC News.

When the barosaurus was alive, he was one of the largest land animals ever to walk the earth; only the blue whale today is equivalent in size.

The ROM's expanded galleries have the space to display him, as well as 25 other fully mounted dinosaur skeletons.

"Dr. Gord Edmunds — that's where 'Gordo' comes from — he had a dream, and I think his dream was to put a big sauropod at the ROM," said May, whose company also built the planets for the Rose Planetarium in Manhattan.

Peter May works on the barosaurus at the ROM.
(CBC)

Edmunds was the curator who presided over the last restoration of the ROM's dinosaur galleries in the 1970s. He'd bought the bones of a sauropod in 1962 with the intention of displaying it, but it proved too big.

"He passed away in the 1990s, and his dream got lost with him," May said.

Well, not entirely lost. The bones he'd bought were in the basement of the ROM, but not properly catalogued.

David Evans, the curator in charge of the current redesign, also went looking for a sauropod, a type of dinosaur the ROM had never before had on display.

He was in Utah, looking over a specimen still in the rock, when he read a reference to a sauropod specimen once sold to the ROM.

That's when May got the call.

Gordo "originally came from the Morrison Formation in Utah and was collected about 1919," May said.

"Some of the bones that came out of the ROM still hadn't been prepared. They still had the original rock around them."

Research Casting began with more than 300 bones — about half the skeleton of the huge barosaurus, which might have weighed 15,000 kilograms when it was living 150 million years ago.

"We sort of did a cut and paste job," May said of the job of putting the skeleton together in a lifelike pose with neck outstretched.

One of the ways the skeleton was re-created was by using bones from a diplodocus, also a sauropod but with a different neck structure than the barosaurus.

Gordo is one of 350 specimens on display from the Jurassic Period (200 million to 145 million years ago) to the Cretaceous (145 million to 65 million years ago), many mounted alongside the flora that would have been natural to their time.

Tyrannosaurus rex is there, as well as a large display of the ROM's rich hadrosaur collection, including a fierce albertosaurus.

Glass walls in the Michael Lee-Chin Crystal give a view of the enlarged galleries from the street.

The new Age of Dinosaurs and Age of Mammals exhibits are in prism-shaped galleries with 5.4-metre-high ceilings on the second floor of the crystal.

The galleries measure 1,450 square metres, large enough to display the largest dinosaurs in displays divided into life on land and life on sea.

Triassic Period fossils (200 million to 250 million years old) are displayed in an adjacent gallery in the historic Queen's Park building. 

The museum has scheduled dinosaur-related events throughout the weekend and over the holidays to encourage families to visit the new galleries.