Thanks to a group of scientists and a unique Canadian workshop, the “Nation’s T. rex” is not only standing for the first time in 66 million years — it’s also eating lunch. The skeleton of the Tyrannosaurus rex that will one day tower over visitors to the Smithsonian’s National Museum of Natural History had previously been displayed only in a horizontal death pose similar to the way it was found in 1988.

The museum’s curator of dinosauria, Matthew Carrano, wanted to bring the prize fossil to life in a way that would convey its ferocity and something about its environment. He and experts at the museum worked with Research Casting International, a cavernous shop full of ancient fossils and power tools, to assemble more than 230 fragile bones into the beast that menaces an unfortunate triceratops nicknamed Hatcher. “There’s a lot of minutiae that built up to the whole mount,” RCI founder Peter May said of the intricate job.

How to build a T. rex from a collection of bones

1 Preparation

After excavating a fossil, preparators use use air scribes, which work like little jackhammers, to chip off harder material. They use water or acetone to soften any remaining dirt, clay or other material in and around the bones and remove it with swabs or dental picks.

2 Repair

Adhesives and consolidants are used to fix cracks and glue broken pieces together, as well as to add a thin protective outer coating. All materials are removable and will not yellow or damage the fossils.

3 Imaging

Every T. rex bone was scanned individually to determine whether it needed repair. Most imaging was done at the museum using handheld scanners that use flashing light to create a 3-D digital image.

4 Molding and casting

Missing pieces are replaced with polyester resin replicas cast from molds. Much of the tail, for example, was cast from molds of other T. rex vertebrae, with a hand-sculpted tip. Cast parts will be painted a subtly different shade from the real fossil so people can tell the difference.

5 3-D printing

A few small replacement parts, such as two ankle pieces, were made from the digital scans of other bones using a 3-D printer. The printer builds pieces by layering glue and gypsum powder.

6 Small armatures

Each bone gets its own cradle, created from various thicknesses of steel rods shaped to hold it without damaging it or allowing it to move. Mounting hardware for a vertebra, for example, looks like the setting on an engagement ring.

7 Large armatures

Unlike the delicate vertebra cradles, which can be shaped cold with a hammer and anvil, the thick brackets for large, heavy bones such as femurs can take a week to create and require heating, bending and welding over and over to get a snug fit.

8 Assembly

Each bone’s cradle is bolted to a thick central steel support rod and can be removed at any time without disturbing other pieces. This also means that no bone supports bones above it; the supporting rods bear all the weight.

9 Tweaking

The assembled skeleton requires minor tweaking, both for scientific accuracy and for practical logistics. Carrano, for instance, requested that a fibula be rotated a bit. The rod supporting the spine was adjusted with a blowtorch to increase the clearance under the tail.

10 Packing

When everything is complete, the T. rex will be taken apart. The armature will be sanded, polished, painted and lined with a sueded polyethelene fabric lining so that no steel touches bone. Fossils will be packed in the custom jackets and crates they came in for their return trip to Washington in 2018.

The challenges of posing a rare fossil

Heavy hips

The joined sacrum and ilia make up the T. rex’s heaviest section at about 1,200 pounds. Because all other pieces flow out and down from this, it is mounted first and the angle and height need to be right. RCI built a plaster jacket and metal mounting frame to hold the massive but fragile bone while a crane hoisted it into place.

Keeping it real

Carrano and other museum experts used a 3-D-printed 1/10th-scale model to work out the logistics of the complicated shifting of the T. rex’s weight as it takes a step. Then they had to figure out how to balance the T. rex over the triceratops without a lot of poles and wires. One creative solution: To avoid an extra support rod, the tail will be attached to a column in the exhibit hall and will appear to float in the air.


The T. rex’s jaws had to be close enough to Hatcher’s frill for dramatic impact but not so close that minor vibrations would cause them to bump and potentially damage each other. This required a lot of bending and reworking of the neck armature to keep the jaws at the perfect angle. This close interaction is one of the reasons the T. rex skull in the display is a cast model rather than the heavier and more fragile original.

Additional sources from RCI: production manager Matt Fair; project manager and master blacksmith Garth Dallman; conservators Boudicca Buteau-Duitschaever and Christopher Hurezeanu; Amelia Madill, head of preparation and conservation; Michael Thom, head of molding and casting, and 3-D technician Christine Findlay. From the National Museum of Natural History: fossil preparator Steve Jabo and Siobhan Starrs, project manager for the new fossil hall.

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