On Exhibit
Digital Dinosaur
Joshua A. Chamot

The bones of the Triceratops at the Smithsonian's National Museum of Natural History in Washington, D.C., have survived for nearly 70 million years. But after a century on display, the 20-foot skeleton has had enough. Exposure to moisture and vibration has weakened its bones, and pyrite has oxidized in others, enlarging within them like a cancer.

Researchers needed to find a way to display the historic skeleton, the world's first Triceratops mount, while preserving its fossils for future scientific study. After two years of renovations, the Triceratops is the centerpiece of the newest exhibition to open at the museum, unveiled in May. Cast from plaster and fiberglass, the new mount is the product of computer modeling and the latest paleontological knowledge.

The impetus to remount the Triceratops came in 1996, when conservator Kathy Hawks arrived at the museum to inspect many of the Smithsonian skeletons. She recognized the critical damage growing within the vertebrate fossils on display - and in particular, in the Triceratops. She warned Smithsonian scientists and staff that time was running out.

The museum staff first thought to treat the bones with hardeners and later remount them with gentler brackets. However, the staff soon saw the renovation as an opportunity to replace mismatched skeletal bones. Assembled in 1905, the original mount was based on turn-of-the-century concepts, and was an amalgam of parts from as many was ten Triceratops and a duck-billed dinosaur known at Edmontosaurus. Many of the bones that were completely missing as fossils were sculpted from plaster. "Almost all of the ribs on the right hand side of the mount were fabricated," says Smithsonian preparator Steve Jabo. "They did all kinds of sculpting to make them fit."

By 1998, when the renovation started, scientists no longer believed that the original posture was accurate. Some errors were obvious, like the excessive bend of the tail, while others would become clearer as studies of computer models and small replicas progressed. Researchers would discover that the animal's 1905 stance was too sprawled, with elbows pointing too far toward the rear of the animal - although the eventual posture would be much less upright than recent Triceratops mounts and illustrations displayed at other museums. The staff wondered how the historical stance could be preserved while somehow incorporating newer findings. The solution came in the fall of 1998, when several Smithsonian scientists and staff attended the Society of Vertebrate Paleontology annual meeting in Snowbird, Utah.

Triceratops, bone by bone

Morphometrics expert Ralph Chapman of the Smithsonian and digital scanning expert Art Andersen of Virtual Surfaces Inc. had been looking for an opportunity to digitally scan an entire dinosaur. Not only can digital files preserve the placement of bones in 3-D space, but they also allow researchers to replicate or make a mirror image of the most accurate specimens and replace missing, damaged or mismatched ones.

At Snowbird, the Smithsonian experts met with Andersen and with Lisa Federici of Scansite. From the start, the project has been a combined effort between industry and several Smithsonian Natural History Museum departments. Private sector companies provided more than half a million dollars of donated services, from scanning and data crunching to digital casting and airline transport. "About three quarters of the budget did not come from us," says the Smithsonian's Chapman. "It came out of donations of time and materials."

Based on a combination of scientific and preservation requirements - and extensive interviews with museum visitors - the Smithsonian decided to create an entirely new Triceratops exhibit within Dinosaur Hall. The exhibit focuses on two scales: geologic, focusing on the dinosaur and its kin, and historic, focusing on the old and new mounts.

The first step was to convert the bones into digital data, capturing details down to a resolution of 0.15 millimeters. While a digital scanning sub-contractor scanned the bones, Jabo, preparator Pete Kroehler, and a number of other Smithsonian staff and volunteers removed fossils from the mount to be treated, molded and taken from the display to the scientific collection. The sub-contractors "fixed them in space like a surveyor," Kroehler says, recording their exact placement in three dimensions and preserving the Triceratops' historical, albeit biologically inaccurate, stance.

Making the scanning process complex was the shape, fragility and bulk of the fossils. "We couldn't take the skull and roll it around," Jabo says. "We had to roll the scanner around it." In all, hundreds of scans were made using three different scanners - one mounted on a flexible arm that could access hard-to-reach places, such as the back of the Triceratops frill. The result was more than 200 files with a combined size of more than 20 gigabytes.

Most of the new mount is cast from the molds of the original fossils, with molding taking much of the project's time, Jabo says. However, because the original exhibit incorporated several mismatched bones, scientists and technicians used the digital data to copy, enlarge and mirror-image accurate bones, replacing errant ones and creating a skeleton that is internally consistent.

Andersen and others edited the files and then sent the data to be engineered by machines normally tasked for the automotive and toy industries. In fact, Hasbro Inc. was one of the contributing firms, producing an accurate plastic model one-sixth the size of the original dinosaur. A cast of the model now stands in the exhibit, mounted in the posture of the 1905 skeleton.

About the size of a small Labrador Retriever, the model was an invaluable tool for the researchers. The Smithsonian shipped casts of several of the scaled-down bones to dinosaur morphology experts. "We sent them the actual miniature bones and said 'just play around with them,'" Jabo says. "Mostly we sent the forelimb posture because that's what we were most interested in: …sprawling or upright?" The experts and Smithsonian staff gathered in the museum to discuss how to rebuild the skeleton with real fossils, miniature replicas and 3-D modeling as guides.

Because the Triceratops now exists as computer files, researchers could animate the skeleton, testing whether the most logical bone arrangements could function in a living, moving animal. The animation process is ongoing, and eventually digital muscles will be added. The first skeleton animations of the newly mounted dinosaur - incorporating what researchers believe is the correct, somewhat sprawled stance - is on display in one of the new videos at the exhibit.

With the added flexibility of high-resolution computer imaging and printing, the staff can now modify the new exhibit, even months after it was assembled. With more than 9 million visitors to the museum in the year 2000 alone, the flexibility ill also allow for quick repairs. "We really build for durability," says Linda Deck of Smithsonian Exhibits.

The family tree

"It's not only been an upgrade to the Dinosaur Hall," Deck says. "[Triceratops] gave us the opportunity to put some dinosaurs on display that had never been on display before." The new mount stands at the center of the exhibit, facing off with the Tyrannosaurus rex across the hall, and surrounded by fossils and casts of Triceratops relatives - including pachycephalosaurs - never displayed at the Smithsonian before. "Pachycephalosaurs are a very major group," says Chapman. "[Now] we have one of the few displays in the world that has four pachycephalosaurs in view."

Many of the vertebrate fossils in the Smithsonian collection need repair, and researchers may one day scan the skeletons just as they scanned Triceratops. "One of them is the 'road kill,'" Chapman says, referring to a Stegosaurus displayed within its matrix as the jumbled bone pile it has been since lithification. "It will be interesting to find out how to scan that," he says.

Chamot is the public realtions assistant at the National Museum of Natural History. He has also written for Geotimes and the Journal of Geoscience Education.

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