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Updated 10:00 AM April 4, 2005
 

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Building a better beast:
U-M scientists reconstruct mastodon skeleton

Combining 13,000-year-old bones with 21st century auto manufacturing techniques, U-M scientists and exhibit preparators at the Exhibit Museum of Natural History are reconstructing a male mastodon skeleton for an exhibit that opens to the public May 21.
(Painting By Robert Thom/Modified By John Klausmeyer)

Meanwhile, museum visitors can peek through special viewing windows to watch preparators assemble the skeleton, which will stand 9 feet at the shoulder and bear 7-foot tusks. The specimen, named the Buesching mastodon for the Indiana family on whose property it was discovered in 1998, will join the museum's female mastodon skeleton, which has been on display since the 1940s.

"To my knowledge it will be the only display in the world with an adult male and an adult female mastodon shown together," says U-M mastodon authority Daniel Fisher, a professor with joint appointments in the Museum of Paleontology and the departments of Geological Sciences and Ecology & Evolutionary Biology.

And while most mastodon specimens are only about 20 percent complete, 70 to 80 percent of the Buesching mastodon's skeleton was found.

"Having even a few specimens as complete as this one removes a lot of the guesswork that would otherwise be involved in studying a larger number of more incomplete specimens," says Fisher, who plans to continue studying the actual skeleton after the exhibit opens.

Paleontologists rarely find complete skeletons, so they're often faced with the task of creating realistic substitutes for the missing bones. Incomplete skeletons are even more common with fossil mastodons because humans sometimes butchered the massive, elephant-like animals and hauled off whole hunks of meat, Fisher says.

In the past, scientists and exhibit preparators used a variety of techniques—borrowing bones from another specimen of the same species, size and stage of development, for instance, or manually sculpting a replacement bone, based on measurements and comparisons with the rest of the skeleton. Now, however, Fisher and his team are using 3D digitization, modeling and rapid prototyping—technologies that are widely used in manufacturing, especially in the automobile industry—to produce full-scale replicas of the bones they lack.

"In cases where there are paired bones in the body, left and right—but we found only one—we can generate the missing bone by making a digital model of the one we have, reflecting it on the computer and then producing a physical prototype of the reflected model," Fisher says. "Compared to all of the previous approaches, digitizing and rapid prototyping are no more expensive, require much less labor and are certainly more exact; more faithful to the original."

In the first part of the process, Fisher and students in the Undergraduate Research Opportunity Program (UROP) created digital representations of each bone using a device called a 3D digitizer, a process that took three years for the whole skeleton. Next, technicians in the UM3D lab made the replacement bones with a rapid prototyping system that converts a digital representation into a three-dimensional, physical object, building it up layer by layer, with each layer only 0.1 millimeter thick.

Crews of UROP students and community volunteers also made molds of the bones, which took about a week for the ribs and almost a year for the skull, says biology undergraduate student Kelly Iknayan, who worked on the project last year. From the molds, students and volunteers then made fiberglass casts.

The skeleton in the exhibit will be assembled from the fiberglass casts so that researchers can continue studying the real bones, on loan to the museum from the Buesching family.

The exhibit also will recognize the American Mastodon as Michigan's state fossil—a distinction bestowed in 2002 after Washtenaw Community College professor David Thomas and students from Ann Arbor's Slauson Middle School petitioned the State Legislature.

Leading up to the exhibit opening, the museum is offering a semester-long series of public educational events, aimed at both adult and family audiences, exploring the theme, "Mastodons and the Ice Age." A schedule of events is available at http://www.
exhibits.lsa.umich.edu/New/Events
.

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