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Backstage Pass to North Dakota History

This blog takes you behind the scenes of the State Historical Society of North Dakota. Get a glimpse at a day-in-the-life of the staff, volunteers, and partners who make it all possible. Discover what it takes to preserve North Dakota’s natural and cultural history. We encourage dialogue, questions, and comments!

Jeff Person's blog

Life of a Fossil: From Death to Exhibit

Have you ever thought about how the many dinosaurs on exhibit in museums across the country got there? What is the journey taken from the time the animal dies until it goes on display? Do all animals become fossils? If the path to becoming a fossil begins at the moment of death, then every plant and animal must run a gauntlet of forces, any of which can stop the process of fossilization.

Picture a Triceratops during its last day on Earth. After giving up the ghost (so to speak), a plethora of forces will begin attacking the future fossil.

First, the Triceratops might be exposed to animals that would like to make a meal out of its remains. This would include scavengers spreading the remains across a large area, wind and rain eroding away the remains, or even small insects and bacteria eating away at the bones. Ultimately, the remains need to be buried quickly, ushering them away from all these potential hazards.

Next, the remains must stay buried for thousands to millions of years. The main forces to avoid during this period are geological. The bones/fossils must survive all the geological forces that could potentially destroy them. These include mountain building, volcanoes, earthquakes, erosion, and landslides (to name only a few).

So is that it? Now that the bones have become fossils, they just wind up in the museum for us to enjoy, right? Not quite.

Now it is time for the remains to come to the surface. This step is really about timing. The fossils must be exposed on the surface and be discovered. Sounds easy enough right? Well, there is a catch. Not only do they need to be visible but they need to be visible to someone who recognizes them for what they are…fossils.

4-step fossilization process

Visual representation of the fossilization process

Did dinosaurs recognize the fossils being exposed at their feet during their time walking the planet? Would you be able to recognize a fossil in the ground if you saw one? More to the point, would you be able to recognize a small part of an exposed fossil in the ground? Often, when fossils are discovered, only a fraction of the bone is exposed, while the rest is still buried under the surface. The fossils must be collected before the elements have had a chance to erode them away. How many fossils of ancient animals simply disappeared because they were exposed at the surface at the wrong time? How many fossils of shells, fish, or ancient reptiles did the dinosaurs destroy because they were walking on them?

Lastly, if you found the partially exposed fossil and recognized it for what it was, could you get it out of the ground intact? Someone could find the most beautiful or significant fossil ever discovered, but if they can’t get it out of the ground without it breaking into dozens or more pieces, they have only a useless pile of fragments-- not something that could go on display at a museum.

The final leg of the journey is entirely reliant on humans. The collected fossils now must travel safely back to a lab or museum, be removed from the remaining rock/dirt matrix, and still be in good enough shape to go into an exhibit. This often means not only the quality of the fossil must be good, but the fossil must also fit into the theme of the exhibit.

T. rex and Triceratops skeleton casts

The dinosaur exhibit at the ND Heritage Center State Museum

The next time you walk through a fossil exhibit, I hope you remember that all the fossils you see on exhibit traveled this path. Do you ever think about what we are leaving future humans to discover about us?

Non-traditional Ways to Find Fossils

When most people think of finding fossils, I bet the image that is conjured in their heads is a lone paleontologist wandering through the badlands, stopping once in a while to examine a fragment of rock or bone. Admittedly this is true in most cases. Some of the techniques used to find and collect fossils in the field are over 100 years old and have changed very little. However, with the advent of new technology comes the testing of new techniques.

Finding a large fossil is one thing. Finding a large fossil and being able to see it from space; well, that is something else entirely. A few years ago a visitor came to the North Dakota Heritage Center with tales of a fossil tree so large you could see it with Google Earth. I will admit that at first I was doubtful, but after very quickly navigating to the location on the computer and seeing photos he had taken from the ground, it did indeed turn out to be a fossil tree.

Fossil tree circle

Image captured from Google Earth. The object in the yellow circle is a fossil tree trunk measuring over 100 feet long.

After some quick calculations, we determined the tree to be well over 100 ft. in length. It is broken along its length into 4-6 foot chunks, some of them likely weighing several hundred pounds each.

I study small mammals. Some of the mammals I study are classified as microfossils (fossils smaller than about 1 cm). Some of these microfossil teeth can be less than 1 mm in length!

Fossil tooth

One fossil tooth from the Brule Formation of North Dakota. This image was captured with a microscope camera. The scale bar represents one millimeter in length.

As you can imagine, finding fossils that small is no easy task. Finding these microfossils starts with a process called screenwashing. This process involves washing collected rock and dirt through wooden boxes with brass screen making up the bottom of the box. The screen openings are smaller than the openings found on most window screens. What remains on the screen after the washing process is dried. Normally it is at this point that the dried material would be picked under a microscope looking for fossils. However, we have added an additional step to the process. Some fossils from certain rock formations will glow under the application of ultraviolet light. The Oligocene age Brule Formation found in North Dakota is one such rock layer. The fossil bone from the Brule Formation glows a bright white, and the teeth from the Brule Formation actually glow a bright orange. Fortunately nothing else found in this formation reacts to the ultraviolet light, just the fossils. This makes finding microfossils from the Brule Formation very easy. Before the washed and dried material is picked under a microscope using white light, we spread the material out on a dark surface and use ultraviolet flashlights to find the teeth.

Tooth hidden among other debris

Washed and dried Brule Formation matrix spread out and ready for picking. The left image was captured under normal, white light. The right image is the exact same spot, under ultraviolet light. Note the brightly glowing tooth in the right image. Can you spot that same tooth in the left image?

This works amazingly well. We have recovered several dozen microfossil teeth using this technique.