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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!

Becky Barnes's blog

Dakota the Dinomummy Makeover

Some of you may be noticing that the “Dakota the Dinomummy” exhibit at the State Museum looks a little . . . different. Don’t worry! Nothing is wrong, we are just in the initial phase of producing a new exhibit for everyone to enjoy. Since Dakota is quite the rarity (one of about six hadrosaur mummies in the world), and because it’s large and difficult to understand what the fossil contains, we decided it was time for a makeover.

Over the next number of months, parts of the current display will be removed for continued preparation and study. The first pieces to go are the arm, one foot, the tip of the tail, and the tail itself. What we call the “body block” will remain on exhibit for a while yet. The pieces that have been removed still have matrix (the unprepared rock) attached, which needs to be carefully chiseled off. The dinomummy as it sits now has had five years of preparation completed. Five . . . years . . . of people sitting around the blocks with pneumatic chisels and magnifying lenses, carefully removing the matrix grain by grain. After five years, there’s still a lot of work that can be done!

When a large fossil is removed from the ground, we have to flip it over to cover the bottom-side of the plaster “jacket.” To avoid damage to the fossil, this usually means that the bottom-side of the fossil is opened and prepared first. This works well, because the bottom of the fossil has had less exposure to destructive elements (wind, rain, snow, cows, etc.). So if only one side of the fossil will be prepared, in this case due to the size, weight, and fragile nature of the specimen — then the bottom is the way to go. The tail will be prepared this way.

Fossilized hadrosaur skin showing small scales

Skin found near the elbow of the dinomummy, with small scales and wrinkles to accommodate movement.

Other portions, such as the arm, are small and stable enough to prepare in-the-round. As you can see in the photos, the scales are vastly different depending on where you look. Toward the elbow, where the skin would stretch and move, the scales are very small, with wrinkles to accommodate movement — much like your elbows (sans scales, of course). The larger scales are found on the back of the arm and are relatively smooth. This would represent the mid-forearm on people, between the wrist and the elbow — an area with no movement.

Fossilized hadrosaur skin showing large scales

Skin found mid-forearm on the dinomummy, with fingernail-sized scales. This is an area between joints, without movement.

If you would like to follow along with the continued preparation of the tail, foot, and arm, we will have periodic updates on Facebook, Twitter, and Instagram (@NDGSPaleo, @ndmuseum). We have to remove as much matrix as soon as possible so we can have the tail 3D scanned. Our goal is to have a 3D-printed, touchable tail for visitors to interact with. The real thing will still be behind glass, but this way the public can truly pet a dinosaur.

Osteoderm Fossils: More than Skin Deep

For most people, the first things they think about when they hear the word “fossil” are bones from some ancient creature. Considering the hard parts of animals fossilize more easily than the soft parts, they have good reason to think so. But did you know that skin can fossilize as well? It is rare, but with the right set of circumstances (the animal is buried quickly, and dries out), paleontologists can find patches of skin. Sometimes, like in the case of Dakota the Dinomummy (an Edmontosaurus on display in the ND Heritage Center & State Museum), paleontologists can find a LOT of skin.

Today, I’d like to write talk about something in between. It’s not a skeleton, but it is bone. And it’s not skin, but it helps shape and support the skin. It’s something called an osteoderm — literally “bone skin.” An osteoderm is a deposit of bone material found within the dermis (skin) of some animals, generally covered by a thicker keratin sheath (the same material that makes up your hair or fingernails). The keratin covering is generally called a “scute.” Different animals have evolved osteoderms, from lizards and frogs to dinosaurs. Rather than focus on an obscure group of animals, however, I’d like to use crocodiles as an example, since most people can visualize them a little easier.

Crocodilian leather with osteoderms

I just *happen* to have some crocodilian leather with osteoderms in place.

If you can imagine crocodile skin (or if you can’t, just look at the image above), it is made up of many square scales. Osteoderms are located under the largest of these scales/scutes. Most of the time when crocodile or alligator skin is harvested for use in the clothing industry, those bony plates are removed in order to insure flexible leather, so people don’t really get the chance to feel the natural armor. The scute is left behind, giving us the look of a large scale, without the backing of bone.

Osteoderms are one of my favorite pieces to find on a fossil dig. They’re small, compact, look like Swiss cheese on the top, and clean up well. In 2013, as we wandered through a fossil site after a rainstorm, I let my eyes wander. As my gaze travelled down one of the now-dry rivulets, I saw six squares of white. Fossils, when they sit out in sunlight for a while, may change color or become bleached. I blinked. Sure enough — I was looking at six little osteoderms all in a row!

Erosional rivulet with osteoderms

Erosional rivulet containing osteoderms bleached white from the sunlight.

Bleached osteoderm

Close-up of bleached osteoderm.

Another site we visit on occasion called Whiskey Creek contains dozens to hundreds of osteoderms. Some are small, and others the size of a large belt buckle. If you’re ever out with us when we find these, you may hear us say “scute” instead of “osteoderm.” This isn’t a slip of the tongue; yes, we know that it’s technically an osteoderm. It’s just more fun (and faster) to say scute than osteoderm. Scute scute scute!

Osteoderm in situ

Osteoderms in situ at Whiskey Creek. The smooth side faces inward, and the Swiss cheese side faces the outside of the animal.

Holding a piece of osteoderm

Mid-sized osteoderm, with hand for scale.