History
The Story
The story started in June of 1992, when Ken Carpenter was having his annual field excursion with volunteers from the Denver Museum of Natural History (now known as the Denver Museum of Nature and Science) in Garden Park near Cañon City, CO. Bryan Small, Ken’s assistant, was searching for fossils with several museum volunteers when he came upon a chance discovery. While searching for microvertebrate fossils, Bryan scraped his rock hammer against a mudstone outcrop of the Morrison Formation and something unusual was knocked lose. To his surprise it turned out to be the fossilized vertebra of a Stegosaurus stenops and after digging a little bit more, they realized that there were more bones buried there.
After discussing the importance of the discovery with Ken, Bryan and the volunteers returned the next day to excavate the site during the remainder of the field camp. They soon uncovered a complete skull, one of only two Stegosaurus skulls in existence at that time! What was even more fascinating was that around the throat of was a patch of quarter-sized bones called ossicles, that acted as throat armor for the Stegosaurus. For the first time they were preserved as they were in life, unlike earlier discoveries that had them scattered all about the skeleton. Due to the rarity and scientific importance of the skull they knew they could not leave the skull at the site when they left. They were worried that if they were to leave it, there was a high chance that the skull could be stolen or damaged. In order to prevent this, the head and neck bones were separated from the rest of the body and encased in a plaster jacket made from layers of burlap soaked in plaster of Paris. The plaster jacket would help stabilize and protect the skull as it was transported to the museum in Denver. With the head safely in their possession, they decided they could leave for a while so they can regroup and prepare to excavate the rest of the body.
The Excavation
For the remainder of June, there was concern that DMNS would not be able to fully excavate the Stegosaur until the next year. Fortunately, they were able to restart excavation in July of 1992 with a team of trained and qualified volunteers from the museum and the Garden Park Paleontology Society (GPPS) led by Bryan and Ken. With the fresh set of volunteers, the crew was able to resume excavation on the skeleton. This was no small task as the Stegosaurus was situated in a steep ravine in a remote area of the Garden Park. Thus, the site was prone to flash flooding and since it was an unusually wet summer, they had to brave thunderstorms on a regular basis. Sunny days on the other hand were not that much better as temperatures were consistently above 90 degrees Fahrenheit (32 degrees Celsius). Sunny days also meant that the gnats would come out to bother the excavators by swarming around them. It was in these conditions that they were required to dig and dig they did. Apart from the skull and a few of the neck vertebra, most of the Stegosaurus was buried under a thick layer of rock. In some areas such as the tail, it was covered by about 15 feet (5 m) of overburden!
A variety of tools were used to remove the overlying rock from the Stegosaurus. For the thicker areas a small electric jackhammer was used, but when they got within a foot or two above the bone only hand tools were allowed so that the fossils were not damaged. The most common hand tool used was the good old hammer and chisel. The technique used was to hold the chisel at a shallow angle so that the
mudstone could be flaked off in small pieces. This allowed for delicate separation of the rock from the bone without causing the bone to be jarred too much. If the bone is jolted by the same impacts as the rock, it can be fractured as well, so care is needed to prevent that. Another concern is the condition of the bone after it has been exposed to the air. Since the air in Garden Park is so dry, exposed bone tends to crumble. To prevent this, a hardening solution is applied to the bone as soon as it is uncovered. The hardener, however, is only a temporary fix. It is important to get the fossils out of the ground and into a lab as soon as possible.
As they dug, the crew uncovered more and more bones. First there were some vertebrae that, like the neck and skull, were still articulated. Attached to these vertebrae were ribs and the Stegosaur’s iconic armored plates! Following the vertebrae further was a pelvis with the hind legs still attached. As the days went by, more rock was removed and the crew finally reached the tail. The tail was another exciting find because it still had 3 of the 4 of the stegosaur’s signature tail spikes still attached to the tail, giving scientists a sense of the orientation they were in when it was alive. The fourth spike, which was broken and later found to have had an infection, was not connected to the tail, but found lying on top of one of the other spikes. It was now that the team figured out that they were looking at a fully articulated dinosaur that was about 80% complete. The only major bones missing from this animal were its two front legs that were likely picked off by scavengers. It was the most complete Stegosaurus ever found!
By now they could see just how big the fossil really was and started to try to figure out how they were going to get the fossil from this nearly inaccessible location in the field to the museum where the fossil could be safely worked. Since it was a nearly complete and articulated skeleton, they were reluctant to break the fossil up into separate sections. It was astronomically rare
to find a dinosaur as complete as this, so if they were to break it up into more manageable pieces, they would run the risk of damaging or even destroying the bones. The head had already been removed and the only natural break remaining was the tail. Still this left the massive body to deal with. Another conflict was that the fossil was situated at the bottom of a steep ravine which would be perilous if they tried to lift such a heavy fossil out of there with a back hoe. After running through their list of options, Ken contacted Dan Grenard of the Bureau of Land Management (BLM) to see if he had any ideas. Dan suggested to Ken that he contact Bill Tezak and crew of Colorado Quarries, who are experts at mining and excavating heavy pieces of rock. Under Bill’s guidance the museum volunteers trenched around the fossil as best they could. Once they had a trench about 3 feet (1 m) deep, thick wooden beams were set up around the fossil to support it for when they would start to remove the rock from under the fossil. After the support beams were set up, Bill sent his men to work with the jack hammers. With the jack hammer, they carved a series of tunnels under the fossil. When they got closer to the specimen, they reverted to using air hammers and hammer and chisel since these tools were less destructive and easier to control. When they were done clearing a section of rock away, they would place up wooden supports under it and hammer them into place. They would then pull out to allow for Ken and volunteers to get under and begin jacketing the specimen.
In order to stabilized the underside of the specimen, a layer of plaster was thrown against the rock, often dripping back down onto the unfortunate volunteer who had to do it. This process is called roofing and provides a more stable surface to apply the burlap strips to. When the plaster had set, half bags of burlap would be rolled up into a bin of plaster, soaking it up, before being thrown up against the underside of the specimen. Gravity always played against this process as every so often the burlap strip would fall off onto the unfortunate soul below. To try and curb this from happening, volunteers had to work fast and with liberal amounts of plaster to keep the burlap in place. After covering the area with the burlap strips, the excess plaster
was smeared over them to smooth it out and reinforce the jacket. Once the plaster would dry, Bill Tezak’s crew would get back under and clear out some more rock and put down timbers before a new section could be jacketed. This process repeated until the entire under side was completely covered. The entire mining process for Bill Tezak and his crew took over 1500 man hours spread across a half dozen workers to accomplish. This would equate to a sum of nearly $40,000 worth of work provided for free by Colorado Quarries.
Now with the Stegosaurus fully jacketed, it was ready to be moved out of there. The only problem was how. As stated before, it would be difficult and dangerous to try and lift it with a back hoe or truck as it weighed about 6 and a half tons (6 tonnes)! So after a few ideas were tossed around, someone suggested that they air lift it out of there. What seemed like a farfetched solution, turned out to be the most viable of all their options. Now they had to figure out where they would get a helicopter big enough to lift the jacket out of the ravine.
The Chinook
Due to the sheer mass of the jacketed Stegosaurus there were very few helicopters that were up to the job. As it turned out, the most suitable helicopter was a CH-47 “Chinook” helicopter whose usual role was lifting heavy artillery in and out of combat. Such a helicopter was used to lifting only 5 tons (4.5 tonnes) in day to day work around the base, but could lift up to 10 tons (9 tonnes) in active combat roles. In order to lift the 6.5 ton (6 tonne) jacket, it would be necessary to get approval from the military to use their helicopter. That is exactly what Ken Carpenter did. He first was able to get in contact with a chief warrant officer at the local military base, Fort Carson. The original request for the lift was that the military was to lift four 1 ton (900 kg) jacketed fossils via sling load out from the quarry and move them to the road. This of course was an underestimate of the actual weight, but though Ken and the rest of the crew were still reluctant to break the fossil up, they always could. The plus side of this was that the lower weight items would make it more likely for the Army to look into and approve their request. The request was handed off to Warrant Officer Robert Wilson, a Chinook pilot and mission coordinator, so he could do a recon on what needed to be lifted and the site where it had to be lifted from.
When Rob came to inspect the site, he found out that the museum had decided that they wanted to keep the Stegosaurus in one piece so he was able to estimate that the weight was over 6 tons (5.5 tonnes). Since the Stegosaurus was a little bit over what the Chinook would normally lift, they needed to get approval from the higher ups. Robert submitted his recon report to Major General Laboa, the acting commander of Ft. Carson and the request was approved by one of his representatives. A date was the set for the air lift to be executed on August 14, 1992.
With only a few days to go before the airlift, Bill Tezak and his crew rigged up the Stegosaurus to get it ready to be lifted. Bill welded on some bolts with a load capacity of over 20,000 lbs (9000 kg). These bolts were connected to a harness of four cables and each could carry over 20,000 lbs (9000 kg) a piece. They were then connected together at the center of the Stegosaurus and could then be attached to the cable from the helicopter.
A Chinook helicopter is more than a one man job to operate. The minimum crew required to operate one is three; a pilot, a co-pilot, and a flight engineer. For a sling load mission there is need for even more crew members. A crew member known as a pathfinder is used on the ground to attach the load to the hook so it can be lifted. He also makes sure everything is attached properly and nothing gets tangled as the helicopter ascends. The flight engineer's main role is to sit in the back of the helicopter and monitor the systems computer to make sure everything is running smoothly. Another responsibility of the flight engineer is to lie on their stomach so they may look down at the hook and payload. While watching the payload, the flight engineer would communicate with the pilots by speaking into a headset. Finally there would be at least one crew member that would look out of side doors to make sure the Chinook was clear of any hazards. For the Stegosaurus Lift Mission, the crewmembers of the Chinook were pilot Ron Nolga, co-pilot David Paasch, co-pilot and mission coordinator Rob Wilson, pathfinder Jeff Floyd, flight engineer Mario Herrera, crew chief Fred Ventura, and crew chief Tim Vice.
The Chinook arrived on the morning of August 14, 1992 and landed about a mile and a half away to receive the lift cable from Bill and discus any remaining details about the operation that was about to unfold. Jeff Floyd, along with several crew members from the Chinook went to the Stegosaurus lift site with members of Bill’s crew to check the rigging and make last minute preparations. After the harness was all set, Jeff stayed down in the quarry while the Chinook crew returned to the helicopter and everyone else moved to a safe place. On top of a hill near the excavation site, dozens of local citizens and news crews were invited to watch the air lift. While everyone watched and waited, the Chinook brought its rotors to life and flew about 400 feet (120 m) above the excavation site, before starting to lower itself into position.
With the Chinook hovering only 100 feet (30 m) overhead, Jeff attached the harness to the lift cable, while everyone else stood back and crossed their fingers. Ron Nolga then slowly pu
shed on the throttle increasing the Chinook's horsepower causing it to ascend into the air. The cable connecting the Chinook to the Stegosaurus started to stretch under the tension and suddenly the Stegosaurus broke loose from its supports, being suspended only by the cable. By using the amount of torque required to lift the jacket off of the ground, the pilots were able to make an accurate estimate of the true weight of their load. Its weight was just over 6.5 tons (6 tonne)! Once free, the heavy plaster jacket swung to one side of the ravine while it tested the strength of the cable. Everyone watched, helplessly, knowing that if the cable snapped the entire effort would have been for not. Fortunately the cable and rigging held as the Stegosaurus was lifted higher into the air. It was finally air born. Most who witness the spectacle seemed to share one common thought, a flying Stegosaurus was the most exciting thing they had ever seen.
The Chinook gained altitude and the Stegosaurus flew over the treetops towards a clearing a little over a mile away where it was set on the ground. The 100 foot (30 m) cable was removed and a shorter cable was attached. This was needed for the next step. Once the shorter cable was set, the Stegosaurus was lifted once again onto a flatbed trailer so it could be transported to the Cañon City Abby for storage.
Now all that was left in the quarry was the tail of the Stegosaurus, but this was no walk in the (Garden) Park. Although the airlift of the body jacket was what all the people came to see, the crew had also excavated the most complete Stegosaurus tail ever found, with its spikes still articulated much like the plates on the body. Prior to the day’s events, the tail had already been fully excavated, jacketed, and prepared for removal. The method of removal that had been decided upon was to use a crane truck supplied by Colorado Quarries that could lift the estimated 3,000 pounds (1,400 kg) the tail jacket weighed.
Late in the evening, the crane truck drove down the road that was bulldozed earlier in the summer. It arrived at the quarry and got into position, while chains were wrapped
around the tail jacket. The chains were then attached to the crane and the tail was hoisted out of the ground, all 3000 pounds (1,400 kg) fighting against it as it was lifted up out of the hole and placed on a flatbed trailer. It was then shipped off to the Cañon City Abbey to be reunited with the body. This Stegosaurus would go on to be the first of its kind to be prepped in its hometown. The previous stegosaurs, such as the ones found by Marsh and Cope were shipped out east, while the Kessler Stegosaurus was prepared in Denver.
The Prep Work
Since there were no traditional prep facilities in Cañon City, it would seem like an odd choice to choose to do the work there. Still the monk at the local abbey was fascinated in the fields of archeology and natural science, and eagerly agreed to allow the use of the abbey’s garage to store the specimen and start preparation. This was very fortunate, because it is important to open the jacket in a reasonable amount of time, because if the specimen is left in a jacket for too long it will start to deteriorate into fragments. The task of preparation was given to Donna Engard, a resident of Cañon City, and a trained paleontology lab technician certified through the DMNS’ paleontology lab certification program. The basics of paleontological preparation are to remove the plaster jacket before chipping the surrounding rock away from the bone, while simultaneously applying hardeners and glues to keep the bone together.
Since a garage at the Abbey was not a conventional place to do paleontological lab work, Donna’s first task was to figure out a way for her to begin her prep work. Prep work was only possible working from the edges toward the center of the specimen, so for most of the time Donna could not sit up. She had to work from above, laying down flat on a board as she worked in towards the center from the edges. The work continued like this through the winter of 1994 and most of 1995 until the Dinosaur Depot Museum would open in 1995, allowing access to better tools, lighting, and an eager crowd of visitors to watch as progress was done on the specimen. It took another year before the prep work was finished on the top side of the specimen.
Once it was completed, the top part was rejacketed so that they could flip it over to do the other side. Bill Tezak was given a call once more for help and the Stegosaurus was transported to Colorado Quarries. Once it arrived at the quarry, they slid the jacket out on to a skid made from 2x4s and secured it with some heavy duty straps. Next, using a bulldozer, they carefully pushed it up against a sand pile while Bill gave orders. After the flip it was returned to the Dinosaur Depot to resume preparation on the, once bottom, side.
After the final bit of preparation work was completed, it was shipped off to its final destination at the Denver Museum of Nature and Science. Three sets of casts (plaster copies of the fossil) were made for display. One was displayed in the Denver Museum’s Prehistoric Journey, a second was presented to the Benson Earth Science’s library at the University of Colorado in Boulder, and a final one returned home to go on display at the Dinosaur Depot. After the Dinosaur Depot closed, this cast was kept within Cañon City and is currently on display at the Royal Gorge Regional Museum and History Center. The actual fossil now rests in the Figgin’s storage facility in the Denver Museum of Nature and Science.