Since the initial discovery of Dinosaur Trackways in the Tumbler Ridge area about two decades ago, there are few locations where Charles Helm likes to go to find fossils.
There’s one place in particular that Helm has been aware of since the early 2000s. “Rocks keep on tumbling down there,” says Helm “It’s an unstable area, and ever spring I go back because there’s more stuff coming down. I’ve been finding more dinosaur tracks every year.”
But about four years ago, he began to see things that didn’t make sense. “There were these parallel raised ridges with funny striations on them. I knew there was something that was happening, but I didn’t know what. I began finding more rocks with these markings on them.”
The rocks looked suspiciously like crocodile trackways that had been found on the Quintette mine site in 2015, but those ones were small. The ones Helm was finding were enormous. If they were made by crocodiles, they would have been eight to 12 metres in length. “It wasn’t a single eureka moment,” says Helm, “but gradually building up of evidence. Over time you just build up confidence. The clincher was finding one large crocodile track. Now we didn’t just have the swim traces, which we use the estimate the size of the crocodiles, but we had this 75 cm long track, which led to an estimate of 8.75 m, which is very close that we were getting from the swim traces. From then on it was just a question of doing justice to what was a globally unique find.”
Two years after he found the trackways—in October of 2020—LaPrairie Crane went out to recover four giant rocks from the sites.
Four years past the initial discovery, and two years since the rocks were brought in to the museum, the research is complete and an article on the fossil traces has been published in the international journal Historical Biology featuring the results from the site: the first track evidence and swim trace evidence ever reported of giant crocodiles.
While the site that Helm visited was the key site for the trace fossils, research was conducted at a number of sites in river valleys and canyons north of Tumbler Ridge.
The crocodiles had been swimming and scratching the muddy bottom with their claws, creating ‘swim traces’.
The traces are from the Dunvegan Formation from the Cretaceous Period and are about 95–97 million years old, from the Cenomanian stage. The large swim traces may represent a precursor to Deinosuchus, a creature found in the fossil record from the U.S.A. and Mexico, though the northern BC crocodiles are older by at least 13 million years.
Evidence suggests the animals found around Tumbler Ridge were about 9 metres long, and possibly as long as 12 metres. By comparison, the record length of crocodiles living today is 6 metres.
“That’s double the length of extant crocodiles,” says Helm. More importantly, he believes these were average sized crocodiles for the period. “We have traces of four or five crocodiles here. We have a sample size of less than ten, whereas the six metre record for today’s crocodiles is from a sample size of thousands.”
In addition to the crocodile swim traces, many ankylosaur tracks were identified, along with ornithopod tracks and turtle traces. The delta environment inhabited by these Cretaceous creatures would have been lush with heavily vegetated wetlands, shallow lakes, and river channels on a flood plain. The area was subject to multiple alternating phases of flooding and exposure, and was about 100 kilometres inland from the marine shoreline of the Western Interior Seaway that linked the Gulf of Mexico with the Polar Ocean.
While the Tumbler Ridge area has become well known for its dinosaurs, there is something special about crocodiles. They did not become extinct at the end of the Cretaceous, but have ‘survivor status’, and are still with us today with a recognizably similar body plan.
Helm also notes that there aren’t any signs of large theropods in the area from around the same time. “Quite possibly these crocodiles were the apex predators in this area during the Mesozoic. When we think about paleontology in this area, it’s not just about dinosaurs, it’s about crocodiles.”
The lead author on the paper was Guy Plint, from the Earth Sciences division of the University of Western Ontario Faculty of Science. Helm says it was fascinating to watch Plint work. “I watched him sit on a rock staring at another rock for an hour, taking notes. There’s that much detail in the rock layers, when you know what you are looking for. He’s setting a new bar for track sites worldwide. I’m not aware of any other research paper that’s gone into this much detail.”
Martin Lockley from the University of Colorado was also co-author on the paper.
But Helm says it is the locals that make these finds so exciting. “People like Tiffany Hetenyi and Lisa MacKenzie and others who came out for a day or two here or there. They spend their days exposing, sweeping, interpreting…we had a lot of fun out there. We have a very good, very dedicated team.”
Helm says while these are not the first crocodile traces in the area, they are quite different than the 2015 Quintette find. “The Teck traces are older, and there are lots of them, but the crocodiles there were much smaller. Those are amongst the best examples of their kind, dating back about 112 million years. These ones date back about 95 million years ago, but the biggest difference is the size. The crocodiles that left the traces at Quintette were maybe one to two metres long.”
And he says, knowing what to look for led him to discover ancient crocodile traces during a recent trip to South Africa.
This is not the end of the discoveries in the area. While he is unwilling to tip his hand, Helm says there are other sites and other discoveries in the area. “This is not the final word on Tumbler Ridge paleontology.”
Trent is the publisher of Tumbler RidgeLines.
