From Field to Museum: How Dinosaur Fossils are Prepared

Wednesday, August 21, 2019

This Triceratops fossil came from the middle of the Hell Creek Formation. It is displayed at MSU’s Museum of the Rockies.  (Photo: Photo courtesy of MSU News Service)

When people think of a paleontologist, they usually picture a grizzled paleontologist gently sweeping dust away from a perfectly articulated dinosaur skeleton. In this scenario, the bones are perfectly preserved, easily distinguishable and seem to be miraculously excavated from the rock around it. The truth is, paleontology isn’t that easy.

In most cases, it is rare to find fossils complete. Most fossils in the field are fragmentary and sometimes only impressions are left behind. In paleontology, context is everything! Field paleontologists know where to seek out specific fossil localities for their research by examining geological maps called topographic maps. From these maps, they can then use a trained eye to read the rocks and identify where fossil bone could possibly be found. When a fossil is discovered during prospecting (hiking all day while looking for cues in the ground), notes and details are immediately recorded about its preservation and location. Pictures of the entire site are taken and everything is well documented before any digging commences. Finally, the fossil is excavated with a variety of tools depending on the nature of the rock the fossil is in. All fossils are found in one type of rock, sedimentary, which comes in all different shapes and sizes from sandy textured grains to more fine grained and compact rock. The kind of sedimentary rock determines the types of tools we use. Some popular tools of the trade include geopicks, jackhammers, dental tools, clay knives, and shovels.

The specimen is usually capped (plastered with burlap) with a hard shell or “jacket” that will protect it during transportation to its final destination, often a museum or university lab. To start this process, a layer of highly specialized paleontological paper (toilet paper!) is applied on the surface of the bone to create a barrier between the plaster jacket and fossil bone. Plaster is then mixed. Layers of burlap are then dipped in plaster and laid on the paper-covered fossil until that side of fossil and rock is fully encased in this “jacket.” The jacket is then flipped over and capped on the other side, totally encasing the fossil and making it ready for transport. Field paleontology is often conducted in remote locations that may not have great road access. Therefore, the team of paleontologists and volunteers may need to work together to manually haul heavy jackets across tough terrain. In some cases, like in the Perot Museum’s In The Field paleontology, helicopters are required to lift and transport heavy field jackets.

Most of the fossil unveiling takes place in a prep lab. Fossil preparators and volunteers uncover and preserve the fossils using specific tools and techniques. Preparators slowly and carefully break away the matrix, or surrounding rock, from a fossil. Some fossils with softer matrix are cleaned with hand tools such as dental curettes. Special reversible glues may be applied to strengthen weak or broken specimens. In the end, fossil preparator’s job is to ensure that fossil specimens are prepared and stored with care to be preserved for researchers, artists and future generations.

By Myria Perez, Assistant Fossil Preparator, Perot Museum of Nature and Science