Oreodont Skeleton Preparation

[32fordboy]

As requested, here is a thread dedicated to the preparation of the Nebraska oreodont. A bit of a backstory before diving into the details of prep work (you can skip the backstory, as it contains no info on the prep process):

It was my lucky week in the Oligocene White River badlands of northern Nebraska, having found a very partial oreodont skeleton the first day of the hunt, then a couple of days later finding two oreodont skulls and a Mesohippus skull all within 150 feet of eachother. None were in that great of condition, but worth the time it took to dig them up.

The other members of the hunt joked about leaving some for the rest of them. So the day after finding the above-mentioned specimens, I went ahead and searched the areas nobody looked at. The areas didn't produce fossils, they said...those areas weren't worth the time, they said. Well, after a lonely day shunned from the rest of the group, I learned they were right. Even loose teeth were far and few between.

Empty-handed and tired of having no human contact in the blistering heat, I made the trek to the other side of the ranch to see how everyone was doing. It was about 3pm by the time I made it down to the flats. Regroup time was 5pm, so there wouldn't be much time to look. Having had a lot of luck already, I really just wanted to stay out of everybody's way, maybe help someone dig up their find.

Well, within 20 minutes of reaching the flats, I spotted a loose toe bone in a little washout. Tracking the washout revealed another toe bone. And another. And some loose leg bits. It's pretty typical to find those miscellaneous bones and not much else, but I slowed down and just started prodding the dirt.

The day after finding the oreodont:

As the story goes, one thing lead to another and I was soon overwhelmed with the realization that I was in over my head with the small amount of time we had left to hunt. Only one day remained to dig it out...and it would take no less than three jackets...and two people to lug out the big one. Can you imagine the looks I got after spilling the beans?

I was able to bribe a friend into helping me dig the skeleton out. In return, she got the first oreodont skeleton I found (very partial...so partial only the skull is worth keeping). She said she didn't need the skeleton in return, but keeping things fair is the name of the game for me.

So now that you've made it through the boring backstory, here are some photos. This will be a VERY stretched out process, so bear with me. The skull is nearly done as of writing this, but the rest of the skeleton will likely go into boxes until I can find the time and motivation to start it up again.

Edited October 22, 2014 by 32fordboy

[32fordboy]

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[32fordboy]

Now is a good time for me to describe the use of Butvar on White River specimens. Mixed very thick, Butvar makes an amazing field prep adhesive, temporarily locking loose bones in place. When applied thick, it can be removed with a razor blade in sheets when the time comes. I DO NOT use it for the final consolidation. For that, I use Vinac.

Another thing I'd like to point out early is the order in which I use super glue (CA) and vinac on the fossils. I've seen most people say to use Vinac prior to CA, as it is known that the acetone in the vinac will eat at the CA. While this is true, I typically use CA first. Working in the automotive painting industry, I don't trust any structural adhesive over a protective coating, as the structural adhesive can pull the protective coating away, rendering both useless.

My line of thought is that while the acetone may dissolve a bit of the CA's outer surface, it usually doesn't interfere with the internal surface of the cured CA. Sometimes, yes, the CA will soften. More often than not, the strength comes back after the acetone evaporates.

The above order is my preference only. I just like having direct glue-to-bone contact with no intermediate layers. it has worked perfectly for me but is, by no means, the only way.

I will describe the Vincac consolidation process when the time comes.

[32fordboy]

After getting the jackets home, I "immediately" tore into them so I could remember what bones were where. For those who don't do their own prep work in a timely manner (or at all), I recommend using sharpie to write the locations of known bones on the outside of the jackets.

Each group of bones was set in a thick coat of Butvar to keep them together until I could get to them with cleaning tools and CA. Doing this allowed me to slowly remove all the bones from the jackets and get a rough estimate of how complete the skeleton was. The bones were labeled and bagged as needed.

I estimate this skeleton is roughly 90% complete.

[32fordboy]

Notice the edited photo above. Red is the shoulder blade, green is the upper arm, blue is the lower arm, and yellow is the hand, down to the hoof cores. Orange outlines the ribs. Prefect articulation!

Interestingly, we can see how the animal died and was buried. The left side of the animal is the side that was “on the bottom” when it was uncovered in Nebraska. The left side of the skull is in amazing condition, while the left side of the skeleton was perfectly articulated, with both the front and rear leg, from shoulder/hip to toe, being in life-position.

The right side of the animal is relatively complete, but scattered, and a few bones are missing entirely. Also note the right side of the skull is not as nice (still very nice, just not near as nice as the left side).

When removing the animal from the jacket, I noticed a lot of the internal clay had raindrop impressions on it. So, combining what we know from the skeleton and raindrops, I’m going to assume the animal died in some fine silt-like sediment on his left side (fetal position) prior to dry conditions.

The silt would have buried the entire left side of the animal, but the right side would have been exposed. The conditions would have dried, hardening the sediment. Then came a bit of rain, leaving the imprints of droplets. Then the surface dried again. By now, I’m assuming the bones would have been starting to dry and weather a bit as they scattered and disarticulated. You can see this on the specimen. Have you ever found an old dried out cow skull and noticed how it was starting to distort and splinter? This specimen was just barely starting to show those signs on the side that would have been exposed. Then came the final burial, sealing up the rain imprints and the now-disarticulated and slightly weathered right half of the animal.

If my assumptions seem wrong, feel free to correct me.

[32fordboy]

Fast forward a bit. Numerous hours later, all three jackets are emptied. I kept all the loose matrix so I can water it down later in search of tiny bits like hoof cores or tiny tail verts.

Now, all bones are stabilized with butvar and labeled in bags. Photos will help later if something somehow gets misplaced.

I'm bored with the bones and ready to clean up the skull. A lot of butvar was brushed onto the visible bone to lock it up tight so the vibration from the air tools wouldn't break anything.

WORD OF CAUTION! Keep your workspace clean and always work over a table. Every now and then a small bit of bone can break off and go flying. You want it easy to locate so you can glue it back on later. Keep your work area swept often.

Using my Chicago Pneumatic and Paleo Aro, clear bone, butvar it. Clear more bone, butvar it again, and so-forth. Eventually, all the larger chunks of matrix will be removed. I did a bit of extra work and separated the jaw halves, as well.

Once the specimen is relatively free of matrix chunks, I used a razor blade to remove the butvar. When a bone came loose, I'd glue it in place. It is very important to make sure the glue surface is clean and the bones fit properly.

I left the "canines", arches, and some other small parts off and labeled. This allowed me to clean the skull better in the micron blaster. Once all parts were blasted, they were glued together with CA. Checking to make sure the blasting work was enough, the three specimens were put in a vinac solution. I mix vinac so it leaves a slight sheen when dry. It is a good idea to make sure the vinac and bone are warm before soaking the bones for thirty seconds or until they quit bubbling. I didn't do so in this case, but it turned out just fine.

WARNING! When using acetone, please be safe. Don't heat it directly, and work in a very well ventilated area. The vapors are harmful to your health and are also incredibly flammable. Dispose of clean-up rags in a safe area, as they can combust. You don't want your house burning down because you didn't take the needed precautions!

[32fordboy]

Here is the skull, ready for putty work. It is 9.25" long.

[32fordboy]

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[Xiphactinus]

STUNNING!

[Kalo]

Awesome!

Thanks for shareing this!

[paulgdls]

One of the most amazing fossils I've ever seen. Thanks for all the info. and for posting. A great story of care in collecting and preparation.

Paul

Edited October 23, 2014 by paulgdls

[Ludwigia]

I've done a lot of prepping on invertebrates. Although I have practically no experience with vertebrates, I can now really appreciate the time, care and precision which is involved. Thank you very much for going into such detail here. I've been able to learn a lot just reading this report. Thanks again. Fantastic results! Now I'm really curious to see how you fit the rest of the jigsaw puzzle together.

[snolly50]

A wonderful project! Please comment on the color of the skull and the nature of the matrix. Your critter is much darker than the ones I have touched. In the background of one of your pictures there appears one that I think is the "typical" color. Are the teeth fluorescent? Thanks for showing this exciting process.

[32fordboy]

Thanks, everyone. A time sheet is being kept so we can see how many hours it takes.

The skull in the background is actually still much more brown than usual...at least for here in Colorado, where White River specimens are an ivory color. Here in Colorado, the matrix is a light tan. In Nebraska, you have two reddish brown layers separated by a white ash layer.

The white ash layer seems to be about the same density as the stuff here in Colorado: hard as rock and it comes out in bricks. It can be dangerous to the bone, which is softer. This is one reason Colorado white River material isn't really worth the effort. For example, my girlfriend just found a Hoplophoneus skeleton on her first-ever fossil hunt (!!!!!). BUT, we were not able to get more than a femur and a toe bone out of the matrix...any effort to remove the hard matrix destroyed the softer bone within. The skull was already nearly 100% washed away.

The reddish brown layers of Nebraska are softer and the matrix comes out in small chunks, usually just popping off any bone surface that is bigger than about one square inch. The bone in this matrix is usually very hard, though the condition of the specimens varies with how long they were exposed before burial. The bones are typically brown within the matrix, but quickly turn white after exposure to the sun. If you find a skull that was half-exposed, it makes for a really neat color pattern.

I'll post more White River material here for comparison purposes. The locations and nature of the matrix will also be posted.

[32fordboy]

Hoplophoneus skull from South Dakota. Found in the 1970s or 1980s. Matrix is light tan and very hard. Luckily, the bone was absolutely solid, making prep doable. It is now fully prepped with the first vertebrae displayed.

Edited October 23, 2014 by 32fordboy

[32fordboy]

Hyracodon skull. A friend's find from the same ranch the oreodont was found on in Nebraska. The matrix is a light tan and I'm assuming medium-hard (I didn't do the prep work). The bone color is a bit more typical for White River specimens.

Edited October 23, 2014 by 32fordboy

[32fordboy]

Here is a personal find from Colorado. The first skull I ever found. Oreodont, obviously. Notice the ivory color. The matrix was hard, but a bit easier to work since the bone was also a bit harder than usual for this location. It was found only about 1000 feet from my girlfriend's very soft Hoplophoneus.

[32fordboy]

Poebrotherium camel jaw found about a half mile from the above oreodont. Colorado. Similar matrix and ivory color.

[32fordboy]

Here are the oreodonts from Nebraska again in individual photos from comparison purposes.

It's difficult to tell if they were in the same layer, since the layers kind of come and go on different areas of the ranch, but I'm thinking the two darker specimens (the second and third skull pictured) came from the brown layer above the white ash, and the lighter specimen (the small one with the lowers attached) definitely came from the layer below the white ash. The matrix on all three was essentially the same density.

The pictured leg bone here came from the small upper skull without the jaw (the last skull pictured). Notice the bite marks from a carnivore. Thanks to forum member Rich White for helping me identify the bite marks a few years ago. An interesting note about the leg bone is that it is multiple colors. That is from certain segments being subjected to sunlight, causing them to turn white.

Edited October 23, 2014 by 32fordboy

[32fordboy]

And here are the Mesohippus and oreodont from the white ash layer. These two were found about 100 feet apart, with the small, light tan oreodont from the post above being about 50 feet away from the Mesohippus, but one layer down.

Notice the generally white appearance of the white ash specimens. Don't let the crumbly nature of the matrix surface fool you. About two inches down the matrix turns into ash bricks.

[32fordboy]

It's a good time to mention that the White River group is broken into two formations, the Brule and the Chadron.

The specimens above all come from the Brule, often referred to as the oreodont beds.

This specimen (Megacerops, aka Brontops or Brontotherium) comes from the Chadron formation of Nebraska (exact location unknown), otherwise known as the titanothere beds.

The matrix of the titanothere beds is remarkably different from the Brule matrix. It is exceptionally green and hard. Often times, bone can only be removed with air tools. The bone color is typically (not always) white or pinkish with grey-blue teeth.

[RJB]

Wow! The way you have described this project is awesome. I was actually getting excited. But its also been about 8 months since ive prepped anything myself. Your work is impressive, both in the field and in the lab.

RB

[fossilhunter21]

Awesome prep and find!