In the footsteps of T-rex and other prehistoric giants: my trip to Hell Creek, the Green River Formation and the Niobrara Chalk

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George Corneille (UK)

It was Christmas 2005 and I received a phone call from the USA from my good friend, Terry Boudreaux. He asked if I wanted to join him and his boys, Christopher and Evan, on a trip to hunt dinosaurs in Hell Creek in South Dakota, fossil fish in Kemmerer, Wyoming and Cretaceous marine life in the chalk formations of Gove County, Kansas. Well, he didn’t have to ask twice and, in June of 2007, I arrived in Chicago to begin my 4,500 mile road trip to some of the most famous fossil sites in the world.

On the morning of Sunday, 25 June 2006, we left Chicago to begin our fossil adventure. I was full of anticipation, dreaming of a finding a mosasaur or maybe a four-inch T-rex tooth (or even just a fossil fly). On the first day, we drove to Sioux Falls, South Dakota, arriving the next day in Rapid City S.D. where I had an opportunity to visit the Black Hills Institute and see their stunning collection of dinosaur fossils. I suppose the most impressive fossil was the complete Triceratops lying in situ, as he has done for the last 65 million years, and the giant skull from a Deinosuchus, the massive prehistoric crocodilian. We continued our journey and, that night, arrived in Buffalo, South Dakota where we would spend the next few days hunting dinosaurs.

Fig. 1. Outside the ranch house in Buffalo, S.D.. Back row from left: Terry, Alyson, Ryan, Steve, Christopher and George. Front row: Evan and Rob.

Hell’s Creek

The next morning, we awoke to a beautiful but very hot day and were immediately greeted by Steve Nicklas and the crew from the organisation Paleo Prospectors. Steve introduced us to Rob, Sula, Alyson and Ryan who would be our guides for the next few days. After breakfast, we headed off in a convoy of SUVs and into the Hell Creek formation, just outside Buffalo, S.D.

The area is best described as being very rugged and isolated. We were prospecting on a large, private ranch that was over 6,000 acres in size. Rob and Steve warned us to be careful, as the area is occasionally visited by mountain lions and rattlesnakes, though they did describe the snakes as ‘gentlemen snakes’ as they always warned you of their presence! Luckily, we never came across any. The first area we searched was a micro-deposit at the base of a steep cliff, the result of ancient river flooding during which the remains of animals were deposited in and around shallow river channels.

During the extreme seasons of the American West, winter snows and rains erode the top and side surfaces of exposures, revealing various fossils, that wash down the cliff. In the first few hours, young Evan (aged nine) found a large, nearly complete Triceratops femur. I found some pristine crocodile teeth and assorted gar scales, while Rob found a beautiful dromeosaur tooth right under my nose! We also found an assortment of other great stuff, but the best find was Christopher’s perfect raptor toe bone. All in all, it was a very enjoyable and exciting first morning’s prospecting of the Hell Creek!

Fig. 2. The micro-deposit site near Buffalo, South Dakota.

Over the next few days, we explored the ranch further and Steve showed us where he had found a huge manus claw from a T-rex. It was in this area that I climbed to the top of a steep cliff and found some nice but fragmented raptor bones that were identified as such because they are curved and hollow. While sitting down for a rest, I also noticed a piece of blue flint that turned out to be a partial arrow point that was approximately 10,000 years old. This area has lots of Indian artefacts and it was fascinating that I had found this at the top of a cliff overlooking an ancient riverbed. Obviously, this was a great vantage point for hunters during the last ice age.

It was an unbelievable experience to walk the dried up riverbeds where giant carnivores once roamed. Many of the places we visited were covered in dinosaur bones. There were Triceratops bone fragments everywhere that were nearly always coloured black. Steve found a beautiful Triceratops brow horn and Terry found lots of skull elements from T-rex; the large cell structure in the bone marrow and the size of the bones are key to identifying tyrannosaur fossils.

I really loved the sense of adventure in exploring the dried up riverbeds, and could not keep my eyes away from the cliffs that bordered them. It was during one of my cliff searches that I made a wonderful find. Rounding a bend in a ravine, my eye was attracted to what looked like a brown patch surrounded by grey matrix, about ten feet up the side of a steep incline. After some careful excavation, a beautiful, complete arm bone of a hadrosaur was exposed, protected for millions of years by a large sandstone capstone. But the precarious position of the capstone could also destroy the fossil (and maybe a bit of my arm as well!) if it collapsed while I attempted to free the fossil. Help arrived, and Alyson and Steve freed it from the matrix while I held the capstone.

Other bones were also found in situ, including rib sections and partial humerus bones. However, they were too deeply embedded to free and we had more ranches to investigate! What was interesting was that all these bones were surrounded by an ash and charcoal deposit that seemed to suggest that this dinosaur was caught in a forest fire 65mya. Since the arm bone was from a juvenile, it seemed that this inexperienced dinosaur did not know how to escape or did not realise the danger it was in until it was too late. This find allowed a small glimpse through a window in time and the bones had a fascinating story to tell.

Fig. 3. Alyson and the hadrosaur bones.
Fig. 4. My hadrosaur bones slowly eroding from the matrix after 65 million years.
Fig. 5. Dr Steve Nicklas and George with the Triceratops brow horn he found that morning.

There were many more interesting finds during our few days in South Dakota. Evan found a partial Triceratops nose horn and some beautiful Champosaurus vertebrae, while Christopher found another dromeosaur tooth. For someone from Northern Europe, I found the heat and humidity at times to be oppressive and the fossil hunting difficult even though I consider myself reasonably fit and healthy. Nevertheless, it was a very productive and enjoyable expedition to the Hell Creek formation – thanks again to Steve and his crew for making this trip a memorable one.

The Green River Formation

A few days later, we were on the road again, driving 475 miles to the Museum of the Rockies in Bozeman, Montana, in the foothills of the Rocky Mountains. While there, we visited the museum and, once again, saw spectacular exhibits including, probably the finest collection of Triceratops skulls in the world, along with the world’s largest T-rex skull. From there, we continued our journey and drove 240 miles through Yellowstone National Park, eventually arriving in Thermopolis, Wyoming.

Fig. 6. George and Terry at the entrance to Dinosaur National Monument, Utah.
Fig. 7. Christopher and George with the bronze statue of  ‘Big Mike’, Dinosaur National Monument.

The next morning, we drove to Kemmerer, Wyoming to join a scientific dig headed by Dr Lance Grande of the Field Museum, Chicago. Dr Grande had kindly offered us an opportunity to assist in a dig for the museum at the Tynsky Quarry, which is located in part of the Eocene Green River Formation (approximately 50 million years old). Dr Grande effectively wrote the book on Green River fossils. It is called Palaeontology of the Green River Formation and is the definitive source reference for them. The quarry is the site where the earliest horse fossil was found and also where the largest vertebrate fossil (a complete crocodile) ever found in the Green River system, was recovered from.

The dig was certainly the toughest part of the trip. We set up camp on top of the mountain where the quarry is located, at about 7,600 feet. The views were absolutely stunning. We could see for miles and watch the thunderstorms and fork lightning in the distance, as well as the coyotes, deer and elk. Each night, we sat around a campfire and talked to museum staff about fossils. It was interesting to have the opportunity to meet and speak with some great people. In particular, we met Akiko Shinya, the Chief Preparator at the Field Museum, who went out of her way to make our stay as comfortable as possible. I also spoke to James Tynsky, the quarry owner, and he recounted the story of the spectacular find of the ‘Dawn Horse’.

On our first morning, we awoke at 6.00am and prepared for the day’s work in the quarry. To say that it was physically demanding would be an understatement. The heat was intense, well in excess of 100oF. The procedure that was used to extract vertebrate fossils is very interesting. Dr Grande would lay flat on the plateau of matrix and, relying on the light and an experienced eye, he marked out the location of the fossils in perfect squares with a heavy pencil. Then, up to 20 assistants, including Terry, Christopher, Evan and I, would drive flattened crowbars into the layers of matrix, which were similar to large sandstone sheets. Everyone would lift and we could end up with a large layer of matrix, maybe ten feet square and about five inches thick.

The fossils were then cut out of the matrix in perfect squares with a consaw that is used for cutting through stone. The whole procedure is very demanding, especially in 100oF+ heat. However, the specimens that were recovered were superb. They included Heliobatis (stingray) and garfish, together with the fossil fishes, Phareodus and Mioplosus. Beautiful examples of the fish, Priscacara, were found, including two by Christopher that Dr Grande kindly allowed him to keep. We also visited Karl Ulrich’s famous gallery where he showed us how to divine water and we saw some of the best vertebrate fossils ever found in the Green River Formation.

Fig. 8. Terry learning to divine water: I wish he could divine some big fossils instead!  Right: the quarry.

The Niobrara Chalk

On Tuesday, 4 July, we left Wyoming and drove 700 miles to Kansas. This took Terry ten hours. We had planned to meet Glenn Rockers, the well-known collector, and to go on a fossil hunting trip in the Niobrara Chalk of Gove County, Kansas. We duly arrived on time and, after spending the night in Oakley, Kansas, we met up the next morning with Glenn. This was my most highly anticipated part of the trip, as giant marine reptiles are a favourite of mine. Well, the excursion was not to disappoint, as we collected lots of great fossils. Christopher found a stunning Ichthyodectes predatory fish jaw after only a few minutes. This was quickly followed by Evan finding some beautiful teeth from the shark, Squalicorax, and lots of fish vertebrae and other fossils. This was to set the tone for a very successful day’s fossil hunting. The day itself was warm, but not too warm and, as a result, it was easier to move around than it had been previously. We found lots of vertebrae from predatory fish that once inhabited the Western Interior Seaway. Kansas and Texas were once covered by this vast inland sea, hence the abundance of marine fossils here.

Fig. 9. The hillside where I found the mosasaur bones.

Glenn has found some spectacular fossils in this area including a complete skeleton of a 25-foot, ancient, predatory shark, Cretoxoyrinha mantelli, also known as the ginsu shark. This shark, along with the giant mosasaur, Tylosaurus proriger, was at the top of the food chain. Add into this mix the giant predatory fish, Xiphactinus audax, and this ancient sea might have been the deadliest of the Cretaceous. We were lucky to find so many teeth and bones from these ancient behemoths and I was also delighted to find my first tylosaur tooth.

Although it was very small and from a juvenile, it was in pristine condition, being just embedded in a soft matrix on a small outcrop. Glenn found some large, partial teeth from Cretoxoyrinha in the same area. However, my best find was of some mosasaur vertebrae eroding out of a cliff, along with a large rib that was broken but which fitted back together perfectly. Hopefully, the rest of the mosasaur is still in the cliff and Glenn has promised me he will go back and try to recover the rest of it.

Fig. 10. Evan, who found the beautiful predatory fish eroding out of the hillside in Gove County, Kansas.

Unfortunately, time had now run out. It was time to leave Kansas and say our goodbyes to Glenn who had been an excellent guide, great company and was responsible for an unbelievable day’s fossil hunting. However, I did have one more person to meet, and it was a meeting I had looked forward to for years – Mike Everhart of ‘Oceans of Kansas’ fame and the adjunct Curator at the Sternberg Museum in Hays, Kansas. We met Mike the following morning at the Sternberg for a behind-the-scenes look at the exhibits. Mike graciously gave us a tour of the preparation labs and it was a memorable experience viewing some of the most spectacular Kansas chalk fossils ever found. The Sternberg contains some of the rarest marine reptile fossils ever collected from the Niobrara Chalk and you can see some of the material online at:

Fig. 11. Terry Boudreaux, Glenn Rockers and George Corneille with the Kansas chalk behind them, July 2006.

We drove back to Chicago from Kansas that day and, a few days later, I travelled back home to Ireland. I am returning to South Dakota and Kansas in July 2008 to go on a dig with Terry and his boys and I am sure it will be a memorable experience. Thanks also to Mike Everhart, Steve Nicolas and Glenn Rockers, and not forgetting Terry for inviting me.

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