New Lives for Old Bones
Guest post by Ben Miller
Dinosaurs and museums go together like chocolate and peanut butter. In the public eye, the image of towering mounted skeletons of dinosaurs and other prehistoric animals is a visual shorthand for museums and what they have to offer. Fossil mounts are an integral part of most paleontology exhibitions, and visitors to natural history museums have come to expect fossils to be displayed in this way. Nevertheless, fossils do not come out of the ground bolted to armatures. Mounted skeletons incorporate actual fossils (or casts taken directly from them), but they are in equal measure human creations composed of steel, plaster and fiberglass. It would be misleading to presume that fossil mounts are unaltered natural history specimens, but it is just as problematic to reject them as forgeries or fakes. As such, these displays occupy a paradoxical middle ground between scientific specimens and cultural objects, and represent a unique set of challenges for educators and conservators alike.
The first mounted skeleton of a prehistoric animal was constructed in 1795 by Juan Bautista Bru of the Royal Cabinet of Natural History in Madrid. The animal in question was a Megatherium (a giant ground sloth) found in what is now Argentina. Fossil mounts continued to be built throughout the 19th century, but these displays were most frequently the work of traveling showmen rather than scientists, and anatomic accuracy generally took a backseat to spectacle.
Fossil mounts as we know them today were an integral part of the rise of large urban natural history museums at the turn of the 20th century. The opening of the American western frontier revealed an unprecedented treasure trove of fossils, far greater than what was previously known from Europe. As a result, paleontology became one of the first realms of science in which Americans were leaders, and patriotism was a significant factor in the growing public enthusiasm for dinosaurs. Wealthy benefactors of recently formed institutions like the American Museum of Natural History (AMNH) and the Field Columbian Museum envisioned the mounted skeletons of these newly discovered extinct monsters as an opportunity to increase attendance and public interest. They provided ample funding for their museums to find fossils for display, ushering in what we might call the “golden age” of fossil mounts.
However, the realities of taphonomy and the fossil record could rarely match the demands of benefactors. The remains of dinosaurs, particularly large ones, are almost never found complete or intact. As a result, fossil mounts have nearly always been composites of multiple specimens, sometimes collected hundreds of miles apart. For instance, the AMNH “Brontosaurus” (now called Apatosaurus) mount was assembled in 1905 from at least four individuals, and a significant number of the bones, including the skull, were best-guess sculptures. As science progressed, that skull (and many other details, including the dragging tail and the number of vertebrae) would prove to be inaccurate, but the mount nevertheless remained unaltered and on display for almost 90 years.
As the 20th century progressed, historic fossil mounts remained extremely popular among visitors, and many took on a second life as beloved cultural symbols. The aforementioned “Brontosaurus”, for example, has been a destination attraction in New York City for longer than the Empire State Building, fondly remembered by generations of AMNH visitors. Nevertheless, as paleontologists’ understanding of dinosaur biology improved, the classic mounts became increasingly obsolete, if not downright embarrassing, for museums in the business of providing accurate scientific information. As interest in paleontology expanded during the “Dinosaur Renaissance” of the 1970s and 80s, however, it became increasingly clear that museums exhibiting historic mounts would need to modernize their star exhibits.
Modernizing classic fossil mounts has proven to be an extraordinarily complex and challenging process. The early 20th century preparators that built these exhibits typically intended for them to be permanent, and the techniques they used were highly destructive. Fossils, including irreplaceable type specimens, were connected to steel armatures by drilling bolts directly into the bone, and broken bones and visible sections of armature were hidden with liberal applications of plaster. What’s more, complete records of which parts of composite mounts came from which specimens have not always survived. In some cases, modern museum workers do not know how many individual dinosaurs make up a historic mount in their care, or even how much of the mount is original bone versus plaster reconstruction. Compounding these problems is the considerable damage most historic fossil mounts have taken during their decades on display. Fluctuating humidity, vibration from passing crowds and the inevitable strain caused by suspending fragile fossils at unusual angles have all taken their toll. Long-overdue conservation assessments revealed that some early-20th century mounts were in danger of imminent collapse before conservators intervened.
In 1999, preparators at the National Museum of Natural History (NMNH) began disassembling and restoring their historic dinosaur mounts, so far completing work on Triceratops, Stegosaurus and Camptosaurus. Restoring a single mount is a multi-year project, as the number of bones in one skeleton exceeds the number of specimens in many exhibits. The NMNH team found that the bolts securing bones to the armatures had often become rusted in place after being exposed to decades of Washington, DC humidity. Attempting to remove the bolts put additional pressure on the fossils and caused them to fracture. Sometimes the bolts were so thoroughly rusted that they had to be cut or drilled out, which put the fossils at risk from vibration damage. Plaster and cement infill could not be dissolved chemically without harming the bones, and had to be chipped away with hand tools. The Stegosaurus proved to be the most challenging to disarticulate. When the mount was built in 1913, an iron bar was threaded through holes drilled in each vertebra. In the process of carefully removing the vertebrae from the armature, most of the neural spines had to be broken off. Causing additional damage to the fossils was heartbreaking for the conservation team, but it was necessary to prevent the catastrophic collapse that would have occurred if the mount stayed on exhibit.
After the disarticulation process was complete, the fossils were stabilized and housed individually in the Museum’s collections, while new mounts assembled from casts were placed on display. Recognizing the inevitable damage incurred by mounted fossils, most modern researchers prefer to display these casted replicas. However, some visitors and even certain museum workers are unimpressed by casts, considering anything less than original specimens inauthentic. It is important to keep in mind, however, that historic fossil mounts also raised authenticity concerns. Consider, for example, the 1905 Triceratops mount at NMNH. As was typical of early fossil mounts, this skeleton was a composite of many individuals of different ages and sizes, some of which were not even Triceratops (Triceratops hind feet had yet to be found, so preparators substituted the feet of an Edmontosaurus). The resulting mount was inaccurate in many details, including a disproportionately small head and excessively splayed forelimbs, but was nevertheless the basis for Triceratops illustrations in popular books for decades afterward. When the original mount was retired, the NMNH team created a casted mount that corrected these problems. The most significant change was the replacement of the undersized skull with larger version, created by digitally scanning the original and 3D-printing it at a different scale. The new Triceratops mount is a much better representation of what a real Triceratops would look like, and yet it is made from foam and plaster. Which version of this display is more authentic, and which version would visitors rather see? This crucial question has yet to be resolved.
Brinkman, P. 2010. The Second Jurassic Dinosaur Rush. Chicago, IL: Chicago University Press.
Carpenter, K. 2012. Dinosaurs as Museum Exhibits. The Complete Dinosaur, Second Edition. Brett-Serman, M.K., Holtz, T.R., Farlow, J.O., eds. Bloomington, IA: Indiana University Press.
Ben Miller completed his M.A. in Museum Studies at the University of Kansas in 2013 and is now the program coordinator at Maryland’s Dinosaur Park. He blogs about the history of paleontology in museums at dinosours.wordpress.com.
Next time on Cracking the Collections:
May 10 – Natural History Notes post by guest blogger Katharine Corriveau