Oreo "Don"

(Click picture to enlarge)

Fully articulated Oreodon (Merycoidodon)

Oreodon, Oreo-don, hence his name "Don"

Discovered in the early summer of 1987

"Don" is the most famous specimen ever discovered on the ranch (Discovered by a guest to the ranch Chris Sampson). Most collected specimens need some type of restoration or reconstruction due to weathering or their exposure to the elements. Don however, has had absolutely no reconstruction of any bones because of his unique positioning in the rock, a mild winter and a heavy rainfall just prior to his discovery. This heavy rainfall exposed only a small portion of the sagittal crest of his skull.



Rarely do you find a specimen of this quality. Don was laying in a natural position of rest or sleep for a mammal. There was no disturbance of location of his bones due to movement of water from a stream or flood. There are no visible signs of broken bones prior to his death or bite marks that would indicate a reason for his death, other than natural causes or exposure.



Below you will see an example of the experience you might have, were you to find an extraordinary specimen like Don.



This sequence of events shows the process from the time of discovery, to the dig, stabilization, plaster jacketing, removal and the final prep. work in the lab.



We only hope that your adventure requires as much work.

The search

"Bones are where you find them"

You can hardly take a step without seeing bone fragments.

Opinion: Most of the best preserved specimens discovered through the years have been found on steep slopes rather than the flat areas. Flat areas tend to have more exposure to the elements while steep slope expose only the edge of a specimen, protecting the remainder deep within the rock bank.

The find

In this photo, you can see tell-tail signs of the sagital crest of the skull.
Before probing or beginning to dig, it is important to flag the bone so you can have a visual orientation while checking down-slope of the bone (first) for any pieces that may be related to your find. Any pieces found down-slope of your find should be carefully bagged and labeled as potential associated pieces to be matched and glued during your prep. work in the lab.
Working from the bottom of the exposure up towards your find can also accomplish several things. It will first give you an indication of whether your find is the last portion of a long exposed piece that has been weathering for many years and it will also keep you from knocking rock on top of crucial pieces related to your find.
Next you should check up-slope of your find to assure that your find is not a float piece that has washed down the slope and redeposited.

The emergence of the skeleton

Once you have done the preliminary scouting of the area up and down slope of your find, it is time to begin slowly removing the overburden from above the find and moving down to the upper horizontal plain of the fossil in a limited area to determine whether there is more of the specimen buried within the cliff wall.
Once this is done, we begin probing with a dental pick or fine blade of our knife to verify whether other bones exist. You can usually discern the difference in feel and in sound as you probe. Bone will have a definitive "tink" sound, where the matrix (the surrounding rock) will have a dull "thud" sound. You can also feel the difference, much like a knife pushing through a hard dinner roll and coming in contact with the plate beneath. Each time another bone is discovered, we remove just enough matrix to determine which bone it is and the orientation of the specimen. In this picture you can see limited amounts of bone exposed, leaving as much matrix on the piece for protection. That matrix will be removed during the final prep. work.
If you discover no further pieces of bone, generally the piece can be removed and wrapped in heavy duty foil for its protection.

Final perimeter and stabilization

I continue probing outward in an expanding radius from the original find until I run out of bone. I usually probe 6" beyond the last bone discovery to ensure that there is not a disarticulated piece laying outside of the perimeter.
Once the perimeter is determined, it is best to stabilize the piece before beginning to dig down and around the sides. There are several materials used to stabilize the bone and the fractures within the rock. Butevar and glyptall are two plastic type beads that can be desolved in accitone. I have always preferred very dilute Elmer's glue. In this picture you can see us stabilizing the entire skeleton with dilute Elmer's glue.
Depending on when the piece was field prepped, at the beginning of the day, how fractured the matrix, and how hot it is, will determine when you will begin digging around the piece. I usually begin the digging process the next day in order to give the satbilizer ample time to harden.

Pedistal the piece in a block

Once the piece has been stabilized, it is time to begin digging around the perimeter to pedestal the piece out. It is best to begin 6" away from the bone and work inward. (Remember. You can always take matrix off.) I usually dig down 10" to 12" depending on how solid the rock is. If not, when the block is removed, everything could slip out of the plaster jacket. Stabilization of the sides are usually necessary at this point however, this is determined at the dig site. Each case is different depending on the size and stability of the block. I usually undercut the block slightly to allow plaster strips to be applied underneath the block.

Applying a barrier

Before applying a plaster jacket, it is imperative to apply a protective barrier between the bone and the plaster jacket.
This barrier is applied to create a buffer between the plaster so it will not stick to the bone. It makes the plaster easier to remove in the lab and also helps to avoid any damage to the bone. Remember when applying the barrier that there must be no undercuts. If there are, when you cut off the top in the lab, it will pull pieces off of the top and possibly damage the specimen.
Some prefer using foil as a buffer. I prefer a couple of layers of wet paper towel. The wet paper towel will suck down around each depression and around each bone, holding it tightly but gently into place. Wet wads of paper towel or cotton can also be used to fill undercuts.

First plaster

Once the buffer is in place, it is time to begin quickly applying plaster soaked burlap strips around the block before the paper towels have time to dry out. I prefer using burlap bags purchased from a local farmers Co-op. They tend to be softer and easier to work with than burlap purchased from a local cloth world. Either will work. Have your strips cut into 6" wide strips, about 3' in length prior to use. On a block this size, I mix up about five gallons of very dilute plaster(about the consistency of thin pan cake batter). Too thick and you will have trouble soaking the burlap. You will need to work quickly in these temperatures or your plaster will begin to harden before the strips are applied. Be sure to push the burlap down and around each nook and cranny. Do not stretch burlap tight as this will leave gaps in the low places. I also criss cross the burlap strips for more strength.

Securing the undercut block

Once you have jacketed the entire piece, you will notice that the underneath sides of the undercut block tend to flap away from the undercut. The last batch of burlap strips should be stretched beneath the undercut block and pulled up over the top of the jacket. This will ensure that you have tight coverage beneath the block before you pop it out of the ground. In this picture I can be seen running my fingers beneath the undercut block until the plaster begins to set.
If there is any plaster left in the bucket, I use it to smooth out the surface of the jacket for a nice look.
The smooth surface also makes it easier to write information with a marker on the jacket.

Removing the find

Once the jacket is dry and hard, it usually just takes a wedge from your pick hoe to release it and a gentle hand to flip it upside down. Remove any unwanted matrix from the bottom side and cap it off with a layer of plaster-soaked burlap to completely encase your find. Here I can be seen sliding the jacket gently down the slope to level ground. Although the specimen is fairly protected within its cast, (much as a broken leg would be in a cast) it can still be damaged or fractured were it to be dropped.

The long voyage home

Some areas are unaccessible, even by quad runners.
But with the use of a couple of logs, a burlap bag and a strong partner, anything can be accomplished.

The one mile trek, up and over several slopes, with frequent breaks took a few hours to reach the vehicles.

Back to the lab

Back to the lab for prep. work.

First job is to cut the top portion of the plaster jacket to expose the fossil for preparation. It is important to leave the block encased within the jacket to assure its stability during the preparation process. I prefer to use Cyanoacrylate super glue for repair of fossils. See supplier in my "Stores for more"

Preparation is a complicated process that is better served in a class environment. I will leave that for another time. Basic prep. work is discussed during evening classes of your dig. In this picture, you can see me working on the final preparation of "Don".