In early September, dinosaur diggers arriving at the Nail Quarry saw nothing but enormous white blobs sticking out of the gray mudstone halfway up a ridge in the middle of nowhere.
The characteristic jet-black color of Late Jurassic dinosaur bones wasn’t visible anywhere because the fossils that had already been discovered were smothered by several layers of tin foil, burlap and plaster, only to be uncovered again in the safety of a museum laboratory.
The white blobs are what paleontologists call jackets. They’re large, awkwardly shaped, covered with sharp edges and extremely heavy, but it’s the best way anyone’s discovered to recover the fragile fossils they discovered.
“Plaster jacketing was invented somewhere in this area,” J.P. Cavigelli, the collections specialist at the Tate Geological Museum at Casper College, told Cowboy State Daily. “I think they used rice flour and muslin back then, but the technique was first used for the fossils found on Como Bluff.”
Plaster jacketing is a vital process at the end of any season of dinosaur discovery. It’s incredibly messy, but everything’s messy in paleontology.
“There was a kid here yesterday playing in the mud,” Cavigelli said. “I think he was being a lot messier than we were. He had mud all over the place. We just had plaster up to our elbows.”
The Only Ones On The Bluff
The Nail Quarry, located on a vast private ranch near Medicine Bow, has hosted paleontologists, amateur fossil hunters and documentary crews for over 30 years. It’s located along a long ridge called Como Bluff, one of the most famous sites of dinosaur discoveries in the world.
Since the 1870s, paleontologists from across the globe have scoured the Morrison Formation exposures on Como Bluff for the skeletons of iconic Jurassic dinosaurs like Brontosaurus, Stegosaurus and Allosaurus. But even amidst this vaunted history, the Nail Quarry stands out.
“There are other nearby ranches that like to claim they’re Como Bluff, but they should be saying ‘Como Bluff area’ since they’re not on the actual ridge,” Cavigelli said. “This is the only active ranch allowing people to dig on the actual Como Bluff.”
The Nail Quarry has attracted a lot of attention for its density of well-preserved fossils. Walter Cronkite poked an oyster knife into the site as the host of the 1990 A&E documentary “Dinosaur!”, and the remarkable discoveries were featured in episodes of the Discovery Channel series “Paleoworld.”
There’s no consensus on what kind of depositional environment created the Nail Quarry. Everything from a log jam in an oxbow river to the discarded dinner scraps from a family of Allosaurus has been hypothesized. More research is needed for a definitive answer.
Today, all the fossils found and excavated in the Nail Quarry have gone to the Tate Geological Museum, ensuring that some of Como Bluff's historical legacy has a permanent home in Wyoming. And the vast majority of those fossils arrive in jackets.
Jacketing
Broken bones benefit from plaster jackets, whether they broke last week or 150 million years ago. Cavigelli explained that jacketing fossilized bones is the same as putting a plaster cast on a living bone.
“When you expose the bones, they tend to want to shatter in a million pieces,” he said. “To prevent that, we put a layer of plaster in burlap around the bones, just the way a doctor would do it on a broken arm when I was a kid. The idea is to keep those bones in your arm from moving. Plaster jackets keep the chunks of dinosaur bones from moving against each other and getting lost.”
While human bones are secured by layers of muscle and fat, dinosaur bones are protected by the rock preserving them. A good jacket incorporates the rock surrounding the fossil, providing a buffer between it and the plaster-soaked burlap.
A small plaster jacket containing a single fossilized bone and several inches of surrounding rock can be extremely heavy. And at the Nail Quarry, it’s never that easy.
There’s nothing small about the fossils in the Nail Quarry, which came from dinosaurs weighing between two and 20 tons. And the quarry’s bone density is so dense that jackets usually have to be expanded to contain multiple bones that can’t be safely isolated in the field.
But when it comes to jacketing, size doesn’t matter. Each jacket will be as large as necessary to extract the fossils safely.
“When they get back to the Tate, we’ll hand them off to our flock of volunteers for preparation,” Cavigelli said. “We have a huge backlog of material and limited space for big jackets in the lab, but they’ll get in there eventually.”
The final trips to the Nail Quarry each summer revolve around jacketing the fossils exposed throughout the summer. The goal is to get everything out as soon as possible, but that’s easier said than done with a dense jigsaw of giant dinosaur parts.
J.P. Cavigelli and Jim McKeeman use hammers and chisels to pedestal and undercut a jacket in the Nail Quarry. (Andrew Rossi, Cowboy State Daily) 
Nail Quarry visitors examine a three-toed theropod footprint preserved on Como Bluff near Medicine Bow. First quarried for its dinosaur diversity in the 1870s, Como Bluff remains one of the richest and most famous dinosaur sites in the world, but the Tate Geological Museum in Casper is the only institution actively digging on the historic ridge. (Andrew Rossi, Cowboy State Daily) 
Visitors digging at the Nail Quarry near Medicine Bow prepare to flip a plaster jacket containing at least one vertebra from a large sauropod. The only way to know what's inside a jacket is to open it open, and that won't happen until it reaches the preparation lab at the Tate Geological Museum in Casper. (Andrew Rossi, Cowboy State Daily) 
Jim McKeeman with the Western Interior Paleontological Society sits next to a recently flipped jacket containing several dinosaur bones. A "clean" jacket is one where there isn't any dinosaur bones sticking out of the bottom, but there's no way to know that until its flipped. (Andrew Rossi, Cowboy State Daily)
The Quarry Queen
One of the most familiar presences at the Nail Quarry is Anita Colin, “the quarry queen.” She received her title from the late James Siegwarth, a retired physicist who discovered the Nail Quarry in 1991.
“I met Jim through the Flatirons Mineral Club in Boulder, Colorado,” she told Cowboy State Daily. “I was very surprised that this quiet old man had a dinosaur quarry. He twisted my arm and told me he needed a new field trip coordinator for the coming summer, so I showed up. That was a very fateful day in my life.”
Colin brought her 13-year-old son Charles to her first summer at the Nail Quarry in 2000. He found a three-foot-long Diplodocus scapula that he couldn’t fully excavate during their first trip, ensuring he and his mother would return for another trip that summer.
Colin has since left Colorado for California, but she returns to Wyoming every summer. She reveres the memory of Siegwarth and continues to diligently do her royal duties as quarry queen.
“I’ve been coming back four to six times a summer for the past 14 years,” she said. “I like to joke that I'm not all that interested in dinosaurs, but I always wanted to visit a dinosaur quarry. I thought it'd be interesting. I visited once, and here I am in my 14th summer.”
In addition to preserving the human history of the Nail Quarry, Colin is the de-facto authority on the dinosaur site. What she says goes, and everyone respects the quarry queen’s authority.
Colin’s first big bone was a Stegosaurus femur she named “Fanny.” Her family has fond memories of uncovering and jacketing “Fanny Femur” and many other discoveries, even if it’s decidedly not their kind of fun.
“My husband came out the first time and helped put a jacket on a bone,” she said. “And then he was like, ‘Well, been there, done that,’ and hasn’t been back since. But finding a perfectly preserved bone and being able to identify and remove it is the height of entertainment for me, so it depends on what you enjoy.”
Undercutting
The beginning of September is a jacket harvest at the Nail Quarry. It’s a veritable Late Jurassic clearance sale, and everything must go (that’s ready to go.)
“We're going to be doing a lot of undercutting this weekend,” Quarry Queen Colin explained to that weekend’s excavation crew, which included Cavigelli and members of the Western Interior Paleontological Society. “They’re very big jackets, but we’ll hopefully be flipping some of them.”
It’s almost impossible to tell what’s in a jacket from the outside. The oversized jackets at the Nail Quarry in early September contained a smorgasbord of sauropod-sized vertebrae, ribs, and unidentifiable chucks.
The only recognizable bone was a five-foot-long scapula, as the jacket was formed around its distinctive shape. That jacket alone could weigh over 300 pounds and wasn’t even the largest in the quarry.
“When I came out here with Jim, we didn’t make huge jackets because we couldn’t possibly deal with them ourselves,” Colin said. “But then the people from the Tate started coming, and JP would say, ‘Make that one whole jacket, and I'll help you get it out.’ So now we're making bigger jackets with a lot of bones right on top of each other since separating them would damage them too much.”
Trenches are dug around each mass of dinosaur fossils until there’s a clear separation between them and anything else. Then, the rock underneath the fossils is daintily removed, a process called pedestalling.
The objective is to remove the right amount of rock. Removing too little rock will make the jacket too heavy and not fully encase the fossil, causing damage. Removing too much rock will remove the fossil’s support, and it could disintegrate or collapse from the bottom.
It’s not an exact science, but the stakes are high enough.
“You want the underside of a jacket to be clean,” Cavigelli said. “You don’t want to see any bone sticking out because that means you left something behind.”
Pancake Batter Plastered
When a fossil (or island of fossils) is isolated and sufficiently undercut, tin foil is wrapped around the edges as the buffer between the rock and the jacket. Then, it’s time to get plastered.
“Never too early to get plastered,” Cavigelli said.
Burlap sacks were cut into long and short strips using “the special scissors,” meaning they were already encrusted with plaster. Then, a small amount of water was placed into a bucket while plaster was poured into it.
“You want pancake batter consistency,” Cavigelli said. “That’s when it’s good for jacketing. But you can only add more plaster, not more water. That sabotages it.”
The burlap strips are soaked with the “pancake batter” plaster concoction and run between clasped hands for an even spread. Then, the soaked strips are placed over the top, along the edges, and on the underside of the isolated island of fossil-containing rock.
The “pancake batter” sets quickly, and whatever isn’t soaked into strips soon turns into “cake icing.” That’s grabbed by the glob and spread across the jacket to add stability and consolidate the several strips into one solid jacket.
Then, rinse (if any water’s available) and repeat as much as necessary. The Nail Quarry diggers got plastered several times throughout the day as the mudstone surrounding the fossils was literally inched away.
A flipped jacket containing a large scapula from a 150-million-year-old Late Jurassic sauropod. The fossil density at Nail Quarry is so high that several bones are pressed against each other, making isolated jackets like this very rare and nearly impossible to accomplish. (Andrew Rossi, Cowboy State Daily) 
Several jackets in the Nail Quarry near Medicine Bow, with Western Interior Paleontological Society member Jana McKeeman for scale. The Nail Quarry is one of the only active dinosaur sites on the historic Como Bluff, which has been one of the most famous dinosaur locales since the 1870s. All the fossil found here go to the Tate Geological Museum in Casper. (Andrew Rossi, Cowboy State Daily) 
Two recently removed jackets sit in the evening sun at the Nail Quarry. Every paleontologist prefers small jackets to large ones, but the deposition and density of the fossils determine the size of each jacket. (Andrew Rossi, Cowboy State Daily)
Flipping Out
Once a jacket is sufficiently pedestaled, undercut, and plastered, it’s time to flip it – the most stressful part of the process.
For the jacket containing the five-foot sauropod scapula, everyone in the Nail Quarry was strategically stationed around the jacket’s exterior. On the count of three, the hundred-pound jacket was pushed onto its topside as quickly as possible, regardless of what happened underneath.
After a jacket is flipped, the first thing someone sees is a bunch of heads rushing in to examine the bottom side. The first thing someone hears is whooping or swearing, depending on the context.
But dinosaur fossils can be stubborn. They might be completely ready to go but determined to remain where they are and are willing to take out their own brethren if forced to move, not unlike a dinosaur-obsessed preschooler on the first day of school.
The good news for the sauropod scapula jacket was that the scapula was completely encased and removed intact. But it didn’t want to go without a fight, and some of its neighbors went all to pieces when it moved.
“I’m not going to talk about it yet,” Cavigelli said as he collected large and small jet-black pieces from the quarry floor where the scapula jacket was sitting. But it’s not all bad, or at least nothing a lot of glue won’t eventually fix.
Winter Jackets
Once each jacket is flipped, the exposed rock on the underside is plastered, completely enclosing the rock and fossils inside. All that’s left to do is load the heavy, awkward masses onto Cavigelli’s trailer and get them to Casper.
By the end of the three-day excavation vacation, four jackets had been pedestaled, undercut, plastered and flipped. They ranged from the size of a basketball to the size of a professional basketball player.
Several jackets remained, as they had grown too large to be finished before the end of the trip. Luckily, jackets serve equally as winter coats for fossils.
“In two weeks, we’ll come back out with eight or ten people to load up these jackets,” he said. “If we can't take them out yet this year, we jacket them to protect them from the ensuing winter.”
Colin added that winter jackets must be strong. The bones might endure many more winters before reaching the safety of a museum storage shelf.
“It can take years to get some things out,” she said.
A Good Place For It
The Nail Quarry might be the perfect place for someone’s first dinosaur dig. Colin certainly thinks so.
“I describe it as a very slow-moving Easter egg hunt,” she said, “because you’re always wondering what’s going to be next. You find the very end of a bone, and then it goes, and it goes, and you think it’s not coming to come out. Then, finally, it has a jacket on it.”
A flipped jacket is a badge of accomplishment after hours and hours of tedious work and an enormous amount of fun for everyone involved. That’s why Colin and Cavigelli try to share the process with every visitor to the Nail Quarry.
“When we ask if anyone wants to jacket, kids and adults, raise their hands enthusiastically,” Cavigelli said. “It's fairly simple to teach people how to expose the bones. It gets more complicated when you get a bone piled up on top of a bone, which is piled up on top of a bone. That part gets a little challenging, but it’s Dino Digging 101, and the Nail Quarry is a pretty good place for it.”
The Tate Geological Museum and the Western Interior Paleontological Society offer a handful of trips to the Nail Quarry every summer. Everyone gets a crash course in Dino Digging 101, and it’s almost always someone’s first time digging for dinosaurs.
Colin hopes to be the benevolent quarry queen of the Nail Quarry for many years. Finding dinosaur fossils on the historic Como Bluff is cool enough, but the majestic beauty and lack of cell service make it a perfect sanctuary from the world for a few days of hard, manual labor.
“It's a very peaceful place,” she said. “It attracts interesting people, the wildlife is amazing, and the scenery is beautiful. I like digging in the dirt here, looking at the landscape, and letting the rest of the world disappear.”
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
