How Smithsonian Fossil Preparators are Re-Excavating a Tyrannosaur from its Past on Display

This National Fossil Day, take an inside look at the effort to free the skeleton for research after more than a century in museum fossil halls

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The museum’s twisted Gorgosaurus skeleton mount as it appeared on display in various fossil halls between 1918 and 2014. Smithsonian Institution

The Nation’s T. rex is tough to miss. The famous Tyrannosaurus rex skeleton, which is posed delivering a bone-crunching bite to a downed Triceratops, has ruled over the National Museum of Natural History’s Deep Time Hall of Fossils since the exhibition hall opened in 2019.

But the Nation’s  T. rex is not the museum’s only notable tyrannosaur. Visitors walking by the FossiLab can catch a glimpse of preparators chiseling away at the skeleton of a Gorgosaurus libratus, an older, svelter relative of T. rex. The creature’s contorted neck and pelvis are entombed in a dense matrix of plaster, burlap and rock. The fossil is not a recent find from the field — the skeleton was found over a century ago and has graced dinosaur halls in both New York City and Washington.

The plaster relief the dinosaur has long been displayed in has made the skeleton cumbersome. “As is, the specimen was hard to access, hard to study, and hard to care for,” said paleontologist Matthew Carrano, the museum’s curator of dinosaurs. So Carrano recently asked fossil preparator Myria Perez and the rest of the FossiLab team to re-excavate the tyrannosaur from its century-old mount.

Perez (far left) and other members of the museum’s FossiLab team pose with the Gorgosaurus skeleton before they begin preparing the specimen. Myria Perez, NMNH

For National Fossil Day, Smithsonian Voices dug into the Gorgosaurus skeleton’s long journey from the badlands to the Smithsonian and the ongoing effort to unearth it.

A Brush with Fossil Hunting Fame

The skeleton hails from the rugged badlands flanking the Red Deer River in Alberta, Canada. These fossil beds, some of which comprise the Dinosaur Provincial Park UNESCO World Heritage Site, preserve the ancient inhabitants of a swampy floodplain that covered the area 75 million years ago during the late Cretaceous period. Dozens of dinosaur species have been exhumed from these rocks, including armored ankylosaurs, burly ceratopsians and sickle-clawed raptors. Gorgosaurus — whose scientific name means ‘dreadful lizard’ — ruled over this prehistoric ecosystem alongside another toothy tyrannosaur named Daspletosaurus.

A close-up of the Gorgosaurus skeleton’s skull before it was removed from its mount illustrates how the fossils were embedded into the plaster display. Smithsonian Institution

The Red Deer River’s rich assembly of dinosaur bones has attracted paleontologists for more than a century. In the 1910s, famed fossil hunters Barnum Brown, who had previously discovered the first T. rex skeleton in Montana, and Charles Sternberg scoured these badlands for spectacular dinosaur skeletons, some of which sported imprints of fossilized skin.

It was Brown who discovered the nearly complete skeletons of two Gorgosaurus individuals between 1913 and 1914. Brown shipped these specimens back to his employer, the American Museum of Natural History (AMNH) in New York City (a third nearly intact Gorgosaurus was discovered by Sternberg and also ended up at AMNH). To prepare them for exhibition, the Gorgosaurus skeletons were partially entombed in plaster and mounted in relief like sculptures protruding out of a wall.
The three Red Deer River Gorgosaurus skeletons in the early 1920s during installation in the American Museum of Natural History’s fossil hall. AMNH Research Library

A Fossil Swap

The 1913 Gorgosaurus skeleton was positioned in the “death pose” in which it was discovered. The tyrannosaur’s head and neck are bent backwards over its hip as its tail, which is largely missing and instead painted on, wraps around its ankles. The dramatic mount was originally displayed at AMNH alongside the other Gorgosaurus skeletons. But the skeleton was deemed expendable. “Brown found quite a few other tyrannosaur specimens in those years up in Alberta, most of which remained at AMNH — and that’s probably why they were willing to trade this one,” Carrano said.

In 1933, AMNH traded the mounted Gorgosaurus, alongside the skeleton of a strange horse-like beast from Nebraska named Moropus, to the Smithsonian for the elongated neck of a Barosaurus, a sauropod dinosaur from Utah. A towering cast of this sauropod specimen now dominates AMNH’s entryway.

The Gorgosaurus skeleton in the museum’s Hall of Dinosaurs and Fossil Reptiles exhibition in 1963. Smithsonian Institution

At the Smithsonian, the pretzeled Gorgosaurus skeleton was first displayed in the Hall of Extinct Monsters in the mid-1930s. The tyrannosaur mount remained a staple as the museum’s fossil hall evolved over the decades. Museum visitors last saw the display in its entirety in 2014, when it was perched on the wall next to an Edmontosaurus skeleton above the museum’s fossil hall. When the exhibition closed for renovations that spring, the Gorgosaurus skeleton and the rest of the museum’s fossilized showpieces were temporarily returned to the collection.

Only the Gorgosaurus’s skull has made it into the new fossil hall. It is now displayed alongside other Canadian dinosaurs from the Cretaceous on the other side of the Nation’s T. rex skeleton.

The Skeleton Gets Dug Up (Again)

Perez prepares the display side of the specimen to be jacketed by wrapping the fragile parts of the skeleton in a thick felt that will be removed when the jacket is finished. This leaves a pocket for the fragile bone so it never touches the jacket. Myria Perez, NMNH

For over a year, Perez and the FossiLab team have been painstakingly freeing the fossils from the plaster mount. Because the fossil was mounted in relief, only one side of the skeleton has been exposed for the last century. The rest has been buried inside an amalgamation of plaster and metal rods to keep the 75-million-year-old bones secured in place.

Before they could chip away at the old display, they had to build a new, permanent storage solution — an archival jacket — to support the fragile fossils as they are worked on and to store them safely in collections in the foreseeable future. These archival jackets are custom made to fit each specimen snuggly and distribute the specimen's weight evenly. For large specimens like the Gorgosaurus, the team incorporates supportive structures into the jacket to keep it from flexing and builds "rockers" to allow the final jacketed specimen to be flipped and observed from each side.

Perez stands alongside a section of the dinosaur’s spinal cord that reveals fossil vertebrae alongside the metal rods that were used to keep the skeleton in place. Jack Tamisiea, NMNH

Once the skeleton was secured, the team has been using air scribes, which act like handheld jackhammers, to remove the original plaster display. “The plaster is pretty easy to remove compared to the rock matrix like it would normally be in,” Perez said.

Perez (right) works with other members of the FossiLab team to prepare the molded jacket to secure the Gorgosaurus skeleton below. Myria Perez, NMNH

As they peel back the plaster, they sometimes find surprises like oversized metal screws, bits of burlap and even some of the original rock the skeleton was buried in along the Red Deer River. “It's very surprising because this side of it hasn't been looked at in over 100 years,” Perez said. “You never know what you're going to find, both fossil-wise and the old mounting techniques that people used.”

The preparators are currently working on a section of the tyrannosaur’s buckled neck and hip and expect to have most of its bones freed by early 2024. The FossiLab team has also been excavating the Edmontosaurus skeleton that was next to the Gorgosaurus mount in the old fossil hall. This skeleton, which was mounted in a similar relief style, is the holotype, or namesake, specimen that all other fossils of the duckbill dinosaur are compared to. This makes removing it for research paramount.

The Gorgosaurus (mistakenly labeled as its close relative Albertosaurus) and Edmontosaurus skeletons in the museum’s old fossil hall. Smithsonian Institution

While the Gorgosaurus is not a holotype, it still has a great deal of scientific value for understanding how these tyrannosaurs lived. “Our [skeleton] is nice because it’s articulated and has some parts of the forearm, plus a nice skull,” Carrano said. Removing it from the old display will make the specimen fully available to researchers for the first time in over a hundred years. “There’s always the possibility for more research,” Carrano said, “especially since no one has really looked at this specimen in a century.”

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