Champsosaur work not finished

An isolated champsosaur vertebrae (middle of the image) that had eroded out of the fossil bearing layer at a site near Climax, August 2020.

This summer a postgraduate paleontology student is going back to a site near Climax in southwest Saskatchewan where he discovered the second-most complete champsosaur skeleton a year ago to look for more fossilized bones.

Jack Milligan is currently working as a summer student at the T.rex Discovery Centre in Eastend. He made this exciting discovery on Aug. 22, 2020 while he was an undergraduate student in paleobiology at the University of Saskatchewan.

He will be starting his M.Sc. studies in the Department of Geological Sciences at the University of Saskatchewan this fall. In the meantime, he is hoping to add more pieces to the champsosaur skeleton during fieldwork trips to the site in the Frenchman River Valley.

The odds of finding fossils are not much better than having a winning lottery ticket and he is very aware that a return to the site might not yield more bones.

“It's always something that we're thinking about,” he said. “That feeling of I'm going to win the lottery today, but there's always that thought in your head of what if we don't find anything significant. Maybe we'll find just little bone chunks that aren't going to tell us much. So it's challenging, because we still find fossils in the same method that people have been using for hundreds of years. It's just taking a team of people and we're just hiking through the badlands with our heads and our eyes looking down at our feet and seeing what's eroded from the hill already and kept following that bone trail up to a layer of rock and then pushing the hill back.”

It was basically what he was doing a year ago when he initially discovered this champsosaur skeleton, just keeping his eyes fixed on the ground. He was taking a break while working on a dig site when he saw a distinctive piece of bone.

“I was stretching my legs a little bit, and I saw one of the backbones of a champsosaur,” he recalled. “I've worked on paleontology digs in Alberta and Saskatchewan over the last number of years, and knew pretty much right away it was a champsosaur, because the top-down view of the vertebra almost looks like an hour glass, and the underside is very smooth. I looked at it and knew instantly what it was. I didn't think anything of it at first until I started finding more and more backbones.”

At first, he was not sure if he had found a skeleton, but that doubt quickly disappeared as he looked closer at the rocks on a hillside. These bones were located just above the Cretaceous-Paleogene (K-Pg) boundary, a benchmark in the geological record that indicates the mass extinction event that wiped out dinosaurs.

“I looked above the boundary and from three metres above, this one hillside was just littered with orange and white champsosaur bones,” he said. “It looked like a waterfall of champsosaur bones was pouring out of this one horizon.”

The purpose of that field trip was actually to learn more about the pre-historic environment that Triceratops dinosaurs were living in, but after his discovery the team focused on recovering as many of the champsosaur bones as possible.

“Those bones could have been washed away if we hadn't noticed it in time,” he said. “When we collected all we could from the surface, we went up to the horizon where the fossils were coming out of, pushed the hill back and found a little bit more of the skeleton, including some ribs and a mostly complete hind foot.”

“Champsosaurs were medium to large-sized semi-aquatic crocodile-like reptiles that existed in Saskatchewan from around 75 million to about 55 million years.

“They kind of superficially look like crocodiles with a long snout and sharp teeth, scaly skin and a long tail, but they actually have no living relatives alive today,” he explained. “They're a completely extinct group of reptiles. These are animals that would have lived in swamps and rivers, and would fed primarily on animals that lived in the water. So animals like fish, salamanders, frogs, those sorts of creatures, and they would have lived in the same environment as crocodiles and large turtles.”

Champsosaurs lived during the time of the dinosaurs, but survived the extinction event that ended the dinosaur period. The environment they lived in was dramatically different from the current grasslands and prairie landscape of southwest Saskatchewan.

“The environment back when this champsosaur was alive would have looked very much like the Florida Everglades,” he said. “So a very heavily vegetated, very hot, humid swamp kind of jungle-like environment. There were lots of tall trees, lots of plants, you know ferns and cycads, and very seasonal. It would have been a dry and a wet season, and an environment with a very sharp contrast to what it is today with endless prairie and grasslands.”

This champsosaur skeleton from the Climax area is about 35 to 40 per cent complete. A skeleton found near Shaunavon is the most complete champsosaur discovered in Saskatchewan. It is about 90 to 92 per complete and is currently stored at the Royal Saskatchewan Museum in Regina.

“One of the things I'm really looking forward to in terms of researching this new champsosaur is being able to compare it to the most complete specimen that we have from Saskatchewan,” he said. “So I'm really looking forward to seeing that, because I've only seen pictures of the most complete specimen.”

The champsosaur skeleton discovered by Milligan is kept at the T.rex Discovery Centre. He has already started to do a comparative anatomy study, during which he is comparing individual bones with those from other champsosaur skeletons, including one that was found near Estevan. The skeleton from the Climax area site does not have many complete bones and through this comparison it is possible to determine more accurately the positioning of a particular bone as part of the overall skeleton.

“We just keep doing that with all the bones that we found from this champsosaur to get a better sense of how complete this animal is and what parts of the body we have,” he said. “We have bones from all four limbs, which is very exciting, a nearly complete hind foot, many bones from the tail, a lot of ribs, a double vertebra, and a couple of bones from the neck. The one part of the animal that we're missing still that would really help with identifying this animal to a species level is the skull.”

An important goal this summer will therefore be to return to the site to look for the skull, but there is uncertainty about whether it is still there.

“The thought in my head is what if the skull was the first thing to erode from the hill and we just missed it,” he said. “So my hope is that the skull is still in the hill. That the animal was buried in such a way that the first things to come out are the ribs and the arm bones and the vertebrae that we found, and then when we push the hill back a little more then the skull will be there as well. That's the dream right now.”

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