At the American Museum of Natural History in New York City, a Barosaurus mother rears up on her hind legs to drive a predatory Allosaurus away from her calf. These fossils may look real, but, in fact, they are lightweight replicas. Reconstructing dinosaur fossils for display in museums is a complicated but fascinating task requiring many different skills and a lot of careful preparation.
PUTTING TOGETHER A DINOSAUR
■ Careful planning is essential before the skeleton is constructed. Every bone is labeled and marked on a plan to show where it belongs.
■ Here the ribs of the Barosaurus are joined to part of its backbone. The backbone is supported by a metal frame.
■ The hind legs and pelvis (hip bones) are lowered into position in the museum by a small crane.
■ The skeleton of the attacking Allosaurus is also assembled. It will face Barosaurus in the display.
MAKING A REPLICA OF A DINOSAUR
There are different methods of making a replica of a dinosaur’s fossilized skeleton. One way is to make a mold of each fossilized bone and use these molds to make a cast.
The fossil is first pressed halfway into a clay base, and liquid rubber (shown in blue) is painted over both the fossil and the base. This will set to form a flexible coat.
Once dry, the rubber is covered with fiberglass sheets. The sheets make the rubber mold rigid enough to keep its shape when it is removed.
Once set, the outer mold is removed. Now a second mold is made in the same way of the other side of the fossil.
The two molds are joined and held together.
The complete mold is filled with liquid polyester or some other lightweight material. This will form a cast.
Finally, the mold can be opened gently. If the technicians have been careful, a perfect cast is revealed.