Volume 4, Number 1 (February 2014) | Research
Fossil Preparation: Extracting a Dugong from the Stone
By Sarah Widlansky | PCP PIRE Intern
The time between when a fossil is collected in the field and made part of a museum exhibit or research project is filled with many painstaking hours of work called fossil preparation. Fossil preparation is the process of cleaning, stabilizing and repairing a fossil so that it can be safely stored, put on display or studied. This process also requires careful documentation of each stage of preparation. This documentation helps the fossil preparators keep track of how skeletal elements or fragments are associated, which can benefit later stages of preparation and research. Each fossil brings unique challenges to the preparation process. The overall preservation of the fossil, including the type of rock it is found in, any natural alteration experienced before or after burial, and the orientation and overlap of the bones dictates how the preparation will proceed.
In 2011, a fossil dugong was found immediately next to the waters of the Panama Canal within the early Miocene Culebra Formation. Although several pieces of the skeleton were recovered, including the skull, lower jaws and part of the vertebral column and ribs, the bones were encased in a matrix of very hard carbonate concretions and siltstone. Since the fossil was excavated, several people have been involved in the ongoing work of preparing it. The bulk of the rock matrix around the bones was removed using a combination of carbide picks, dissolution in a formic acid bath and microscribes. Microscribes—sometimes referred to as airscribes or microjacks—are handheld pneumatic tools similar to tiny jackhammers. Now that much of the matrix has been removed, the delicate process of exposing details and separating bones begins. To be as careful as possible, we work under a microscope to gently remove the matrix from the fragile bone edges.
Documenting each stage of preparation of the Panama dugong has not been straightforward. Typically, photographs are sufficient to record the relative position of bones and the amount of matrix that has been removed. In this instance, however, photographs have been of limited help because both the bone and matric are dark brown with speckles of gray and lighter shade of brown. This similarity in color combined with the lack of depth in the photos makes it difficult to see the textural differences between the bone and rock.
Consequently, we have been experimenting with a three-dimensional laser scanner to document the preparation process. The computer models of the partially-prepared fossil dugong are uniform in color, but show the textural differences between bone and matrix, and are less expensive to create than a series of physical molds and casts. Additionally, these models are more accurate than a typical scientific illustration and are being used to advance our research on the dugong even while it is still within the stone. Documenting these intermediate steps between discovery and display or publication can further be used in outreach programs and exhibits to lend greater transparency to the detailed work and scientific process underlying paleontological studies.