Natural History Highlight - USA National Museum of Natural History

Click here to view QuickTime movies of Triceratops.
http://www.nmnh.si.edu/paleo/dino/trinew.htm

Scanning the Bones

Ralph E. Chapman, head of NMNH’s Applied Morphometrics Laboratory, initiated the scanning work. He teamed up with Arthur Andersen, head of Virtual Surfaces Inc., Mount Prospect, Illinois and Lisa Federici of Scansite 3-D Services, San Rafael, California, to develop the project and digitize the bones. The first step in the process was to digitize key points in the original dinosaur mount before it was disassembled so that if need be, it could be restored to its original position. Next, each bone was scanned by Henry Wede of Steinbichler-Dimension Data by means of a surface scanner. Then individual computer files were built for each bone, leading to more than 200 files, equaling at least 20 gigabytes of data.

The History of the
Original Specimen

(Click to see larger image)

Triceratops with Norman Boss, upon
completion of move to NMNH

How did Triceratops come to be on exhibit? The story goes back over 100 years. In 1888, John B. Hatcher was working in Wyoming for the famous paleontologist, O. C. Marsh, professor at Yale and Vertebrate Paleontologist for the United States. While in the town of Douglas, Hatcher was introduced to Charles A. Guernsey, owner and manger of the 999 cattle ranch. Mr. Guernsey showed Hatcher some examples from his considerable collection of fossils. Among them was a fragment of a very large horn core that had been taken from a skull several feet in length which had been found by the ranch foreman, Edmund B. Wilson, at the bottom of deep canyon on the ranch in Converse (now Niobrara) County. Owing to the press of business, Guernsey offered to conduct Hatcher to the locality at some future time. During the following field season, on May 7, 1889, Mr. Wilson escorted Hatcher to the canyon and showed him the remainder of the skull belonging to the dinosaur that Marsh was to name Triceratops that very same year. Between 1889 and 1892, Hatcher collected bones from at least 50 individual horned dinosaurs in Wyoming, more than 30 of which included parts of the skull. Much of that material became part of the United States Geological Survey collections, which were then transferred to the Smithsonian Institution where they are currently part of the collections of the NMNH Department of Paleobiology.

With assistance from Hatcher, who had trained them on their first job at the Carnegie Museum of Natural History, two new arrivals at NMNH, Charles W. Gilmore (later to become a curator in the Museum) and Norman H. Boss (later to become Chief Preparator) used some of these bones to construct the world’s first mounted skeleton of Triceratops. Their mount was just under 20 feet long and just over eight feet tall at its highest point. It went on display in what is now the Arts and Industries Building in 1905, and eventually was moved to the Dinosaur Hall of the Natural History building after the building opened in 1910. This mount has served as a model around which the current concept of Triceratops, the living animal, was interpreted, although the ideas of what Triceratops looked like and how it lived have varied considerably through the years.

The extensive data files started as large clouds of location points in three-dimensions, representing the external surface and characteristics of each bone. Arthur Anderson used the scan points first to built a virtual model of each bone; and then the final, composite skeleton, composed of three-dimensional images in the computer.

New Bones from Old

Knowledge accumulated about Triceratops’ anatomy since 1905, and compromises due to the composite nature of the original mount were accommodated prior to prototyping new bones. The Museum’s staff knew the dinosaur’s left humerus, or upper forelimb, was a smaller mismatch to the right humerus, and that the back feet were from a different dinosaur group altogether, the skull was too small for the body, and other bones were also mismatched in size or so fragile that they should not be on exhibit. Arthur Anderson created a new, full-sized version of some of the problematic bones: the left humerus, left ilium, and left scapula, by making mirror images of the complementary bone from the opposite side. Satellite Models of Mountain View, California, constructed full-size replicas of the mirrored bones by using a material called Ren Shape, which was then reproduced by making molds, and casting the final versions to be used in the mount. The prototyping process involved using the computer data files to direct the milling of a block of Ren Shape with progressively smaller and more accurate drill heads until the final product was a very accurate representation of the original. Also, a miniature prototype was made by Jason Dickman, of Hasbro, Cincinnati.

During disassembly of the skeleton, Jabo and Kroehler determined that the skull of NMNH's Triceratops was too small for the rest of the body by about 15 percent, based upon studies of the proportions of the various bones of the body from other articulated specimens. These findings led to an April, 2000, consortium of paleontologists being convened at NMNH to determine the animal's proper posture and articulation when alive, and examine the miniature prototype of Triceratops. Kent Stevens, Rolf Johnson, Kathy Forester, Brenda Chinnery, and NMNH staffers Michael Brett-Surman, Ralph Chapman, Steven Jabo and Peter Kroehler met at NMNH for a day of discussion, comparisons and the best kind of intellectual "play".

Using the 1/6 scale prototype, they could easily manipulate the model and test different ideas about Triceratops’ range of motion. NMNH staff were exploring the various postures Triceratops could take as they planned for the new mounting. The paleontologists compared the computerized scans of Triceratops’ bones with the different positions using the miniature prototype, and shared a sense of what a skeleton of a complete single Triceratops should look like.

To remedy the disparity of bone size, posture, and articulation for the new mount, data were exchanged with Shared Replicators and Tulsa Technology Center to create a prototype of an enlarged version of the original skull, using a form of stereolithography that produces high-resolution versions of the original in lightweight plastic material. This process uses a laser to shape and cure a light-sensitive epoxy-resin

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Dinosaur specialist Mike Brett-Surman among the collections. Photo by Chip Clark

Conserving Dinosaurs

When they are not on exhibit, virtually none of the Museum’s ninety or so genera of dinosaur fossils is kept as an assembled skeleton. Instead, their components have individual “jackets” or storage supports. These jackets are made by specially trained museum technicians and conservators who build a removable shell of plaster and fiberglass, padded with an ethafoam lining, custom-made for each bone. Each jacket protects one specimen, providing some buffering against vibrations and variations in temperature and humidity. The jackets also make handling these large, heavy fossils much safer and easier to do.

How do vibrations and swings in temperature and humidity hurt a fossil? Fossilized bone can still absorb moisture. Temperature and humidity changes affect bone and yield results much like the “heave and thaw” effect seen in the ground during the freeze-thaw cycles in winter time. Vibrations, even if they seem unnoticeable or minor to us can literally shake a museum specimen apart over time. When these two types of damage are combined, the results can be disastrous for the long-term preservation of a museum specimen.