Evrim Yazgin
Cosmos science journalist
About 100 million years after the animals that left them behind died, researchers have found the world’s first footprints from club-tailed dinosaurs.
The most famous and largest of this armoured, herbivorous group of dinosaurs is Ankylosaurus – a creature built like a tank that could grow to 8m long, 8 tonnes and have a beach ball-sized, solid bone club at the end of its tail.
Ankylosaurus belongs to a bigger group of armoured dinosaurs called ankylosaurs. The 2 main families within this group are nodosaurids and ankylosaurids. Nodosaurids lack the rigid tails or formidable weapon on the end of some ankylosaurids’ tails.
Nodosaurid trackways have been found over the past hundred years. These tracks are a type of trace fossil, or ichnofossil, given the name Tetrapodosaurus borealis. This name doesn’t belong to a specific dinosaur species but is the ichnospecies name of the tracks themselves.
The new trackways found in the Canadian Rocky Mountains are unlike the Tetrapodosaurus.
Tetrapodosaurus tracks have 4-toed footprints. The new footprints have 3 toes. The discovery is detailed in a paper published in the Journal of Vertebrate Paleontology.
The 3-toed tracks are a sure sign they were left behind by an ankylosaurid dinosaur, making them the first to be found anywhere in the world. The authors, therefore, name a new ichnospecies: Ruopodosaurus clava, meaning “the tumbled-down lizard with a club/mace” referring to the mountainous location of the fossil tracks.
“While we don’t know exactly what the dinosaur that made Ruopodosaurus footprints looked like, we know that it would have been about 5–6m long, spiky and armoured, and with a stiff tail or a full tail club,” says author Victoria Arbour, curator of palaeontology at the Royal British Columbia Museum in Canada.
“Ankylosaurs are my favourite group of dinosaurs to work on, so being able to identify new examples of these dinosaurs in British Columbia is really exciting for me.”
Ruopodosaurus tracks were found at 2 sites: Tumbler Ridge in British Columbia (BC) and in northwestern Alberta.
The tracks date to 100 to 94 million years ago. No ankylosaurid bones had been found in North America from 100 to 84 million years, leading some palaeontologists to speculate that the family had disappeared from the continent at the time.
The new tracks show that club-tailed ankylosaurids were thriving in North America which they shared with their nodosaurid cousins.
“Ever since 2 young boys discovered an ankylosaur trackway close to Tumbler Ridge in the year 2000, ankylosaurs and Tumbler Ridge have been synonymous,” says co-author Charles Helm, scientific advisor at the Tumbler Ridge Museum.
“It is really exciting to now know through this research that there are 2 types of ankylosaurs that called this region home, and that Ruopodosaurus has only been identified in this part of Canada,” says Helm.
“This study also highlights how important the Peace Region of northeastern BC is for understanding the evolution of dinosaurs in North America – there’s still lots more to be discovered,” adds Arbour.
