Displaying objects as heavy, fragile and complicated as large articulated fossil skeletons requires a great deal of engineering and metalworking expertise. We’ve been dismantling historic skeletal mounts as part of the Deep Time exhibit renovation project, and in the process fossil preparators in the Department of Paleobiology and NMNH conservators have learned a lot about the array of fossil mounting techniques used by our predecessors during nearly 150 years of exhibit building. This series of posts, based on a recent presentation by preparator Michelle Pinsdorf, describes different styles of mounting and considers their advantages and disadvantages in terms of aesthetics, specimen conservation, and, for lack of a better word, “convenience” for those of us tasked with taking the mounts apart.
External Armature Mounts:
When displaying fossils in an exhibit, how can a balance be achieved between exposing surfaces for viewing, and at the same time supporting the specimen to prevent damage? One method developed to address this problem is the external armature mount. Metal rods are bent to conform to the contours of a specimen, and brackets or adhesives secure the specimen to the support structure. External armature mounting techniques have been refined over the years and are now the preferred method of exhibiting fossil specimens. Major and unique advantages of external armature mounts are that they protect the fossils from the types of damage described in my earlier posts, and improve accessibility for research on the displayed specimens.
The larger a fossil mount gets, the heavier both the specimen and its armature become. The mounts of Orohippus pumilus (USNM V26305, built circa 1958) and Diplodocus longus (USNM V10865, built circa 1930) offer good comparisons between mounts for lighter and heavier specimens.
In modern external armature mounts, archival-quality coatings are applied to the metal frame to prevent corrosion and chemical interaction with fossils and the exhibit environment. Padding is used wherever contact could occur between fossil and metal, to prevent damage. Another innovation is the use of removable brackets, which allow individual bones to be taken from the mount, while the rest of the skeleton remains independently supported. This ensures that researchers can access all parts of the specimen for scientific study without disrupting the overall display.
Over the century-plus history of the NMNH fossil displays, the worth of external armature mounts has been proven in many aspects. The majority of full skeletal mounts from the old Fossil Halls that are returning to display have been completely dismantled, and new external armatures are being crafted for them. This allows for great flexibility in terms of designing the new exhibit and presenting these creatures in lifelike and dynamic positions. It also ensures the specimens will be protected and remain scientifically useful throughout their next chapter of public exhibition. We look forward to previewing more specimens and their mounts as work on the new Fossil Hall continues!
All photos by the author except the Diplodocus full mount photo by Jim DiLoreto/NMNH Imaging and the T. rex tail photo by Steve Jabo