When you think of dinosaur fossils, you probably picture parched deserts or badlands scorched by the Sun. But one of the world’s richest dinosaur graveyards is buried in a less likely setting: a quiet patch of forest in northern Alberta, in Canada.
It’s called the Pipestone Creek bone bed, and it’s home to tens of thousands of bones – all from a single, bizarre-looking species of horned dinosaur called Pachyrhinosaurus.
The site, and the mystery around why so many of these animals died at once, is the focus of a new episode of Walking With Dinosaurs – the landmark BBC series returning to screens after more than two decades.
We spoke with Prof Emily Bamforth, a palaeontologist and curator at the Philip. J Currie Dinosaur Museum in Alberta. Her research on Pachyrhinosaurus features in the new series – especially where it employs cutting-edge technology to find out exactly what happened when a catastrophic event that wiped out an entire herd.
The dinosaur with a boss
Pachyrhinosaurus is no household name – yet. But it’s one of the most distinctive members of the ceratopsian family, which includes the more familiar Triceratops.
“They’re a smaller, older cousin,” Bamforth said. “But instead of having a horn on their nose, like Triceratops, they had this huge bony mass we call a ‘boss’. They’re the only horned dinosaur that has that.”
So far, three species of Pachyrhinosaurus have been identified – all from northern latitudes, in places like Alaska and Canada.
These dinosaurs, which could grow over 6m (20ft) long and weigh more than two tonnes, migrated in enormous ‘megaherds’ numbering in the thousands. Bamforth compares this to modern-day caribou migrations – only on a far grander scale.
The fossil site they left behind is just as colossal.
“There are upwards of 10,000 individuals preserved here,” Bamforth said. “It’s one of the densest bone beds in North America – we’re talking 100 to 300 bones per square metre, and the site stretches back into the hill for at least a square kilometre. It’s a hugely dense bone bed that is very, very large – and that makes it tremendously significant.”
A mystery in the mud
With such a high concentration of fossils, the question is: how did so many dinosaurs die in one place, at the same time?
“The story of this particular herd of Pachyrhinosaurus is ultimately a tragic one,” Bamforth said. “We know they all died at once in some kind of catastrophic event, and we know that whatever killed them wiped out almost every member of the herd indiscriminately – big, little, old and young.”
The mass die-off happened around 72 million years ago – well before the asteroid impact that famously wiped out the dinosaurs.
“We think it was a catastrophic flooding event,” Bamforth said. “Possibly from monsoon rains in the nearby mountains, or even a hurricane-like storm washed inland. It would have been similar to flash flooding events that happen today, but on a massive scale.”
The result was a disaster for the dinosaurs – but a scientific windfall. The sudden burial preserved a remarkably intact snapshot of the herd, including individuals of all ages: a single moment in time captured in extraordinary detail.
And it wasn’t just palaeontologists who benefited. “There’s evidence that theropods like Albertosaurus and smaller raptor-like dinosaurs scavenged the carcasses after the flood,” Bamforth added. “It would have been a smörgåsbord for them.”
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Lessons from Pipestone Creek bonebed
Finding one dinosaur skeleton is rare. Finding thousands in a single layer? That’s virtually unprecedented. And it’s giving scientists the chance to ask questions that are usually impossible in dinosaur palaeontology.
“Usually when we study dinosaurs, we find one or two – if we’re lucky, maybe there’s a dozen,” Bamforth said. But, given the sheer volume of fossils that are all from a single herd, Pipestone Creek offers a rare window into what's known as intraspecific variation: the natural differences between individuals of the same species.
Just as no two people look exactly alike, Pachyrhinosaurus are likely to have varied in size, ornamentation and behaviour. Bamforth and her team are especially interested in the frills that crown their skulls – structures that appear to differ subtly from one individual to the next.
“We’re coming to understand that almost every Pachyrhinosaurus had a slightly different frill,” she explained. “We think maybe that helped them recognise each other in the herd.”
The bony bosses on their noses also varied significantly. What they were used for – whether for combat, attracting mates, recognising other individuals, or a mix of all three – is still under investigation.
A field in fast forward
Since the original series of Walking With Dinosaurs aired in 1999, palaeontology has changed dramatically, with Pipestone Creek just one of many windows opening into prehistory.
“The focus used to be on just finding dinosaurs and describing them,” Bamforth said. “Now there’s more of an emphasis on understanding their relationship with the world they lived in.”
That shift has been driven not just by advances in technology, but also, in part, by public fascination. “Dinosaurs are more popular now than they’ve ever been, and because of that, the field of palaeontology is moving at a tremendous pace,” Bamforth said.
If Pipestone Creek proves anything, it’s that dinosaurs still have plenty of secrets to share – even after 72 million years.
About our expert
Emily Bamforth is a palaeontologist and curator at the Philip. J Currie Dinosaur Museum in Alberta, Canada. She is also an adjunct professor at the University of Saskatchewan in Saskatoon, Saskatchewan and the University of Alberta in Edmonton.
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