Scientists have identified fossil dinosaur footprints from a new species in B.C. and Alberta. They’re believed to be the first tracks found in the world to be identified as belonging to club-tailed ankylosaurs, offering new insights about gaps in the fossil record.
The new species, which has been named Ruopodosaurus clava, would have been an armoured dinosaur about five to six metres long, reports a new study published this week in the Journal of Vertebrate Paleontology.
Victoria Arbour, curator of paleontology at the Royal B.C. Museum and lead author of the new study, said Ruopodosaurus would have lumbered through the coastal redwood forests between the Rocky Mountains and an inland sea that covered Saskatchewan and Alberta during the Middle Cretaceous, about 100 million to 94 million years ago. Previously identified footprints suggest the other creatures it lived alongside: giant crocodiles, duck-billed dinosaurs and bird-like dinosaurs — and a related group of four-toed ankylosaurs.
But no bones of three-toed, club-tailed ankylosaurs have ever been found in North America from the Middle Cretaceous, which, until now, suggested they may have gone extinct during this time, before reappearing about 84 million years ago, perhaps by the migration of populations from Asia. The tracks from this new species suggest otherwise.
This species, Arbour said, is “new for North America. It’s new for the world…. And it really helps us fill in this gap in the fossil record.”
A tale of two ankylosaurs
Like two-toed and three-toed sloths, there are two closely related branches of ankylosaurs with different numbers of toes:
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Ankylosaurids, which have three toes, and are famous for their tail clubs, which were either slim and stiff like a baseball bat, or round like the one on the famous well-preserved ankylosaur Zuul crurivastator, which lived around 75 million years ago.
Victoria Arbour, an evolutionary paleontologist at the Royal BC Museum, describes how some armoured dinosaurs likely used their horns, spines and armour for fighting each other, not just for protection.
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Nodosaurids, which have four toes, a flexible tail, and a longer snout. Many had big shoulder spikes, including Borealopelta ankylosaur, a well-preserved specimen found an an oilsands mine in 2011.
Borealopelta fossilized so perfectly that we can see every inch of its armour and skin in 3D, 110 million years after its death.
Nodosaurid prints were first found at Tumbler Ridge by two boys, 11-year-old Mark Turner and eight-year-old Daniel Helm, in 2001. That led to the discovery of other dinosaur trackways and fossils in the region, and the founding of the Tumbler Ridge Museum.
What scientists learned about the new species
Arbour first saw photos of the unusual tracks in the new study about five years ago. Some were found near Tumbler Ridge and others at a gas well on the other side of the B.C.-Alberta border.
“I thought they were really strange and interesting looking and I was really curious about them,” she recalled.
Then in 2023, she visited the Tumbler Ridge Museum, and Charles Helm, Daniel’s father and the scientific advisor at the museum, suggested they study the tracks together, along with some new ones that he and Daniel had found. Many included not just three-toed footprints, but the crescent-shaped, five fingered handprints that ankylosaurs are known to have.
“And I got really excited,” Arbour said. “I was like, ‘You know, I think the only thing these really can be … is an ankylosaurid.”
The research confirmed that, and named the new species Ruopodosaurus clava, which means “tumbled-down lizard with a club/mace” referring to the location they were found and the distinctive feature of this ankylosaur family.
Arbour said fossils found in China suggest that at this time, tail clubs were just starting to evolve in ankylosaurids, so this species may not have had a full round club like Zuul.
Almost all the footprints were similar in size — about 30 centimetres long — suggesting that the average size of this species was about five or six metres long, or smaller than many ankylosaurs without tail clubs. Sometimes multiple trackways were found together, all heading in the same direction and never crossing, suggesting several animals may have been travelling together.
Anthony Shillito is a University of Saskatchewan researcher who has previously studied dinosaur trackways from the Cretaceous that included four-toed ankylosaur footprints. He said footprints from three-toed ankylosaurs may have been found before, but there are so many three-toed dinosaurs that they would have been hard to identify without the distinctive handprints that were found with the footprints in Canada.
“[The study] really made me think back to some of the footprints I’ve seen — maybe I misinterpreted it because I didn’t have this information,” he said. “Now people have a better idea of what they’re looking for.” And that may lead to more being found, and a better idea of where else these club-tailed ankylosaurs may have lived during the Middle Cretaceous, he suggested.
The value of footprints vs. bones
Paleontologist Scott Persons studied both fossil dinosaur tracks and ankylosaurs during his PhD at the University of Alberta, and is currently working on the study of a new nodosaur species.
He said in showing that ankylosaurids lived in North America earlier than thought, the new study demonstrates the value of looking at both fossil footprints and bones. Those often get preserved under different conditions and contain different information.
“If you only look at fossil bones, you may be missing half the puzzle pieces,” said Persons, curator of the Mace Brown Museum of Natural History and assistant professor at the College of Charleston in South Carolina.
He noted that trackways often show multiple species that lived together at the same time, and can reveal other information. This new trackway also shows that wide, squat ankylosaurs — sometimes described as being coffee-table-like — had a surprisingly bird-like gait, lining up left and right feet like “supermodels on a runway.”
He added, “This track record shows us the coffee table analogy is a little bit flawed.”
On the other hand, he acknowledged, there is one drawback of footprints compared to bones.
“The obvious question is: What do these animals look like? All we have are the feet.”
