Ancient Seaway Yields Unique Fossil Discoveries
Big Bert had a coming-out party this summer. Bert is long dead, having expired about 90 million years ago. But the ancient crocodile still has his fans, among them, Canadian Museum of Nature palaeontologist Dr. Steve Cumbaa.
After all, it was Cumbaa and Royal Saskatchewan Museum palaeontologist Tim Tokaryk who had discovered Bert 20 years earlier along Saskatchewan's Carrot River, near Pasquia Regional Park, and where Bert's skeleton was unveiled to the public this past summer. Cumbaa even co-authored the scientific paper that classified the unique six-metre long carnivore, giving it the name Terminonaris robusta.
That lucky find in September 1991 heralded the start of a broad, collaborative research project for the Canadian Museum of Nature that has since uncovered thousands of bones of fish, sharks, marine reptiles, ancient birds, dinosaurs and invertebrate marine life from an ancient sea known as the Western Interior Seaway. This large marine sea corridor bisected North America about 100 to 65 million years ago, leaving behind countless fossils that pepper parts of Saskatchewan, Manitoba, southern Alberta, the Northwest Territories and the US Midwest.
And so it was that, 20 years on, Cumbaa found himself passing by Bert's new home on a two-week fieldtrip in Manitoba and Saskatchewan in August 2011. He was joined by Carleton University graduate student Danielle Dionne and museum fossil preparator Alan McDonald for what will likely be the veteran palaeontologist's last foray to some of the seaway's fossil locales. "We were trying to sort out some of our final questions on the origins of these bone beds, to learn how and why they accumulated and what role they can tell us about the evolution of the seaway," explains Cumbaa.
There is certainly enough to go on. Cumbaa's lab space is teeming with some of the tinier fossils that have been gathered over more than 12 field expeditions to one of Canada's unique palaeontological regions. And it was all sparked during those initial Carrot River trips in 1991.
"Tim and I were walking along the riverbed, wading and climbing rocks, looking for fossils sticking out of the shale," explains Cumbaa. He stopped to snap a photo of an impressive exposure of shale, and asked Tokaryk to stand on top of it for a sense of scale. Tokaryk, however, was bending down, distracted. "No! No! I need you to stand up!" Cumbaa recalls yelling to his colleague. "Well, I just found a bone," proclaimed Tokaryk, who is now the Head of Earth Sciences at the Royal Saskatchewan Museum. That bone turned out to be part of Big Bert, just one of the more impressive animals that they would find in the area.
"The reason these bones are known at all is due to a local farmer, Dickson Hardie, who owned the land. He kept finding chunks of rock with fossils and teeth in them and brought them to Tim for examination," says Cumbaa, who had been developing a specialization in fossil fishes at the time and caught wind of the finds. A collaboration with Tokaryk soon followed. "Tim recognized the potential of this material, because it had shark teeth, bones of other fishes, little bones of plesiosaurs, and most interestingly, bones of birds," explains Cumbaa. "We knew it was marine, and nothing was really known from that area"
What the keen-eyed fossil experts had stumbled upon was a bone-bed, a dense accumulation of bones representing many species and animal groups. "Usually in shales, you find an isolated bone here and there and occasionally a more complete skeleton, usually flattened. But in this spot we kept finding concentrations of bones."
The researchers worked two to three years in the Carrot River and Pasquia Hills region, and then began to look further afield for other fossil sites. "We started looking through geological records, at all the other hills, to see if there were similar records of bone beds being found," explains Cumbaa.
That quest has since taken Cumbaa, research assistant Richard Day (now retired), fellow museum palaeontologist Dr. Xiao-chun Wu and others to about a dozen locations in the Prairies. These are not only in Saskatchewan's Pasquia Hills, but also in Manitoba, notably along the hills of the Manitoba Escarpment, which include the Porcupine Hills and Riding Mountain. It was in these areas that Cumbaa and McDonald collected more specimens this past summer, about 150 kg of material that is awaiting analysis.
It's been time well spent, as the researchers have uncovered a rich diversity of fossils, traces of life entombed in the rocks that were once mud at the bottom of the ancient seaway. Highlights have included the oldest birds known in North America. "We've found hundreds of bones of birds in good condition, representing about five species from about 95 million years ago. This was totally unknown in Canada, and certainly represents the most diverse bird fauna known from North America for that time period." Cumbaa is also proud of the tantalizing bits of marine reptiles known as plesiosaurs that have been found, as well as new records for many of the fish and sharks, including several new species.
The diversity makes the project appealing. "One of the things I really enjoy about this work is that I am able to look at this area much more broadly and look at it as an entire ecosystem with all the fauna, both micro- and macroscopic. We have certainly described species new to science, but I am even more pleased that we are able to characterize the palaeo-environment, and to some extent begin to understand the palaeo-ecology of this sea," explains Cumbaa.
Cumbaa was able to take his research into the seaway and create a strong presence for it in the museum's fossil gallery that opened in 2006. Casts of a plesiosaur, mosasaur and a giant turtle share space with fossil fish and bird bones to convey the impressive marine diversity that existed so many millions of years ago. There is even a cast of Big Bert's skull.
And with two decades' worth of collected fossils to study, there are still new discoveries coming. Much of it is being achieved in collaboration with scientists across Canada, the United States and Great Britain. Says Cumbaa: "We're working back in time, to a time much older in the history of the seaway than anybody has worked before. It's been great working with people that have different specialities and to put together the picture of what this Western Interior Seaway looked like."