A group of scientists has uncovered what they think is the first fossil linked to the asteroid event that wiped out dinosaurs from the planet. The fossil, a dinosaur leg, is “stunningly” preserved and even has skin attached. It’s part of a larger group of remains that were found at the Tanis fossil site in North Dakota, United States.

The leg belongs to a Thescelosaurus, a group of upright bipedal dinosaurs from North America, and scientists now believe it was killed alongside many others on the actual day a giant asteroid struck Earth 66 million years ago. Not many fossils have been found in sediments dated to a few thousand years before the asteroid impact, let alone at around the moment it occurred, which is wh the Tanis site, located 3,000 miles away from the actual asteroid impact site in the Gulf of Mexico, is so intriguing.

The BBC has spent the last three years filming at the Tanis site for a documentary narrated by naturalist Sir David Attenborough. It will be broadcasted on April 15^th. Robert DePalma, a UK researcher who leads the Tanis dig, and Phil Manning, who is DePalma’s supervisor, recently presented their findings at NASA Goddard Center.

“We’ve got so many details with this site that tells us what happened moment by moment, it’s almost like watching it play out in the movies. You look at the rock column, you look at the fossils there, and it brings you back to that day,” De Palma, who works at the University of Manchester with Manning, recently told the BBC.

Dinosaurs and a massive asteroid

It’s widely accepted that a 12 kilometers-wide asteroid hit Earth to cause the last mass extinction, wiping out all dinosaurs. While the impact was identified in the Gulf of Mexico, the devastation was felt far and wide, including on the Tanis site – which first emerged in the public sphere in 2019 after an article from the New Yorker Magazine.  

Researchers believe the remains of animals and plants at Tanis were rolled together into a sediment dump following river water waves triggered by tremors. Ocean organisms were even mixed in with land-based creatures. Alongside the dinosaur leg, Tanis has offered many other intriguing fossils such as a turtle skewered by a stake.  

While the work of De Palma and Manning is part of a documentary, they have also published some of their findings in peer-reviewed papers – with many more to come as they go through the process of extracting, preparing, and describing the fossils. They have also worked with outside consultants to examine their findings for the TV show.

Paul Barrett from the Natural History Museum is one of them. He has looked at the leg and agreed it is from a Thescelosaurus. “This looks like an animal whose leg has simply been ripped off really quickly. There’s no evidence on the leg of disease, there are no obvious pathologies,” Barrett told the BBC, suggesting the animal died suddenly.

The big question is then whether the dinosaur died on the same day the asteroid hit the planet, as a consequence of the catastrophe. De Palma and Manning believe this was the case. But some remain skeptical, such as Steve Brusatte from the University of Edinburgh, who was also involved as an outside consultant for the BBC documentary.

Brusatte told the BBC he would like to see the arguments in more peer-reviewed articles, and for paleo-scientists from different fields to go into the field to give their assessment. He said it’s possible that animals that had died before the impact was unearthed by the violence of the asteroid and then re-interred in the soil, for example.