Reconstructing a dinosaur skeleton is a complex job as usually only a fraction of the skeleton is recovered. Palaeontologists assume the missing pieces will resemble those of the animal’s closest relatives, and use these as guides for making replacement parts. Most excavated fossils are too delicate to put back together, so technicians construct a lightweight replica of the skeleton, which is then erected in a life-like pose. Rearing on its hind legs, the American Museum of Natural History’s Barosaurus is the world’s largest freestanding dinosaur exhibit.
With its head rearing more than 15 m (50 ft) into the air, the Barosaurus skeleton was mounted on a supporting metal frame. It took two hydraulic lifting platforms to assemble it safely. First the tail sections were joined together in their upward-curving shape. Then the tail’s metal frame was welded to the frame of the hind legs. The huge ribcage followed. The assembled head and neck section was then raised above the body.
The teams operating the two lifting platforms had to work very closely when the neck was ready to be fitted to the body. Suspended by strong ropes from the upper platform, the long neck section was inched downwards, with men on the ground pulling on ropes to help control its movement. A worker on the lower platform guided the neck’s connecting rod until it finally slotted into a tube in the body’s frame.
Throughout the assembly process, welders worked quickly to ensure that fitted sections of the support frame could not come apart again. Care was taken to shield the bones from hot sparks, which could set them alight. After a section of the frame was welded, part of the replica skeleton was fitted over the weld, hiding it from view.
The awe-inspiring spectacle of the mother Barosaurus protecting its young from a ferocious Allosaurus greets visitors when they first enter the museum. Scientists believe that such a scene could have occurred 150 million years ago, but it cannot be known for certain. The replicas stand on a bare surface that, like the dinosaur skeletons, was produced by a moulding process. Latex rubber was painted onto rocky ground in Montana; when the rubber mould had set it was peeled away and later used to make a cast of the rocky surface.