Dinosaur leg might be from the day the asteroid struck, scientists claim

This is an ongoing story and will be updated.

An immaculately preserved dinosaur leg uncovered in North Dakota may be a relic from the day a massive asteroid slammed into Earth, bringing the age of the nonavian dinosaurs to an end, scientists claim. That said, not all experts are convinced that the dino actually died on that fateful day 66 million years ago.

A team led by Robert DePalma, a doctoral student at the University of Manchester, uncovered the fossilized leg, which still has skin attached. Based on where the leg was found in the fossil deposit, the team suggested that the dinosaur died and became buried during the famous asteroid impact, BBC News reported (opens in new tab). The specimen has not yet been described in a peer-reviewed scientific journal. 

According to Paul Barrett, a merit researcher at London's Natural History Museum, the leg belongs to Thescelosaurus, an herbivorous dinosaur whose name means "wonderful lizard" in ancient Greek. "It's from a group that we didn't have any previous record of what its skin looked like, and it shows very conclusively that these animals were very scaly like lizards," Barrett told BBC News. "They weren't feathered like their meat-eating contemporaries." 

Based on his examination of the fossil, Barrett said the dinosaur's leg was likely ripped off very quickly, and the limb bears no signs of disease or having been picked apart by scavengers. Barrett examined the fossil on behalf of BBC One, which will soon premiere a documentary (opens in new tab) about the North Dakota site where the specimen was recovered.

BBC One also called in Steve Brusatte, a vertebrate paleontologist and evolutionary biologist at the University of Edinburgh in Scotland, as an outside consultant on the project. Brusatte told BBC News that he's skeptical of the idea that the Thescelosaurus perished on the exact day the dino-killing asteroid came whizzing through the sky and punched a huge hole, known as the Chicxulub crater, into the Yucatán Peninsula. 

Related: What happened when the dinosaur-killing asteroid slammed into Earth? 

It's possible that the Thescelosaurus and other animals discovered at the North Dakota site died days or years before but were violently uncovered during the asteroid impact and then reburied along with debris from the planet-rocking event, Brusatte said. 

The North Dakota site, known as Tanis, has drawn similar skepticism in the past, Science magazine reported (opens in new tab) in 2019. 

That year, Robert DePalma, then a graduate student in paleontology at the University of Kansas, and his colleagues reported finding at the site fossilized fish whose gills were riddled with small glass spheres called spherules. These freshwater fish included sturgeon and paddlefish and were found jumbled together in a 4.2-foot-thick (1.3 meters) deposit, surrounded by scattered remnants of tree trunks and thick mud speckled with more glass spheres, according to Science.

—Fossil 'death pit' preserves dino extinction event … but where are the dinosaurs?

—Dinosaur-killing asteroid triggered mile-high tsunami that spread through Earth's oceans

—How long do most species last before going extinct? 

In their 2019 study, the team determined that these glass spheres were about 65.8 million years old and theorized that they formed from molten rock that was flung into the sky during the Chicxulub impact. They suggested that the fossilized animals at Tanis were initially deposited there by violent seismic waves that radiated from the impact site, some 1,860 miles (3,000 kilometers) away, Science reported.

"Those fish with the spherules in their gills, they're an absolute calling card for the asteroid," Brusatte told BBC News. "But for some of the other claims — I'd say they have a lot [of] circumstantial evidence that hasn't yet been presented to the jury." 

In addition to the glass-filled fish, the team has reported finding the fossilized remains of a turtle and small mammals; the skin of a Triceratops; a pterosaur embryo locked inside an egg; and a fragment of what might be part of the impact asteroid itself, according to BBC News.

"For some of these discoveries, though, does it even matter if they died on the day or years before?" Brusatte said. "The pterosaur egg with a pterosaur baby inside is super-rare; there's nothing else like it from North America. It doesn't all have to be about the asteroid." 

Originally published on Live Science.