Scientists now know that a massive Yucatan asteroid struck the earth 66 million years ago at the end of the Cretaceous Period, ultimately causing most species of dinosaur to go extinct.

It was the sudden change in climate that accompanied this disastrous astronomical collision that made the earth unlivable for these cold-blooded reptiles, leading to the complete disappearance of creatures that had roamed the earth for more than 100 million years.

But there were some dinosaurs who didn’t meet their demise as a result of catastrophic post-asteroid climate change. These dinosaurs lived in what are now known as the Americas, within the range of the impact zone of the Chicxulub strike, which occurred in the Gulf of Mexico just off the northern coast of the Yucatan Peninsula.

These hapless creatures would have been destroyed immediately or soon after the earth-shattering Yucatan asteroid impact, unable to withstand the unimaginably destructive forces unleased in the wake of this planet-killing calamity.

Now, for the first time, paleontologists have uncovered fossilized remains from one of these dinosaurs, an animal killed by the direct physical effects of the Yucatan asteroid, the single most destructive event in the earth’s history.

While excavating at the Tanis fossil site in the state of North Dakota, in what is known as the Hell Creek Formation, a team of explorers working under the direction of University of Manchester paleontologist Robert DePalma uncovered the fossilized leg of a Thescelosaurus, a small lizard-like herbivore from the late Cretaceous Period.

Amazingly, the leg was intact and still covered by fossilized skin, suggesting that whatever force had removed the leg had been incredibly powerful and concentrated.

“This looks like an animal whose leg has simply been ripped off really quickly,” Professor Paul Barrett of the Natural History Museum in London, told the Daily Mail. “There’s no evidence on the leg of disease, there are no obvious pathologies, there’s no trace of the leg being scavenged, such as bite marks or bits of it that are missing.”

The Hell Creek Formation , and the Tanis fossil site it contains, were created in the aftermath of the Chicxulub asteroid strike , 66 million years ago. The Yucatan asteroid created an impact creator that was 93 miles (150 kilometers) wide, and its collision with the earth sent out echoes of mass destruction radiating in every direction from ground zero.

North America was hit by seismic waves equivalent to those generated in a magnitude 11 earthquake, and soon after by inland waves that were as powerful as those created by the most destructive tsunami.

The Thescelosaurus was apparently killed in a sudden and exceedingly violent fashion, even though the asteroid’s point of impact was approximately 1,900 miles (3,000 kilometers) away.

Putting all the pieces together, it seems clear that the Thescelosaurus was an early and immediate victim of the Yucatan asteroid impact event, which ultimately killed off not only the dinosaurs but up to 75 percent of the animal species living on the planet at that time.

The discovery of the severed dinosaur leg is groundbreaking, paleontologists say, because no other dinosaur fossil has ever been linked directly to the most catastrophic event in earth’s history.

“This is the most incredible thing that we could possibly imagine here, the best case scenario, the one thing that we always wanted to find in this site and here we’ve got it,” Robert DePalma told the BBC. “Here we’ve got a creature that was buried on the day of impact—we didn’t know at that point yet if it had died during the impact but now it looks like it probably did.”The paleontologists have been able to reconstruct what happened at Hells Creek Formation after the Yucatan asteroid hit. Following the asteroid strike, rising sea levels and tsunamis would have created an inland sea to the north.

The process that created this sea also would have spawned at least two massive, towering waves that moved so far inland that they actually reached what are now the lands of North Dakota. These enormous waves washed over the Tanis site, and eventually covered the animals that died there with up to six feet (1.8 meters) of sediment.

Between the first and second of these waves, glass beads called tektites would have been raining down from the sky like tiny ballistic missiles, reaching speeds in excess of 200 miles (320 kilometers) per hour.

It is possible one of these tiny but deadly glass pieces struck the ill-fated Thescelosaurus with enough force to slice off its leg and kill it, although this is just one possible explanation for the creature’s death.

Tellingly, the sediment layer at the Tanis site eventually turned into a type of clay rich in iridium. This substance is rare on earth, but asteroids and meteors have it in abundance.

The amazing story of the Tanis site will be introduced to the British public on April 15, when BBC One will broadcast a new documentary entitled “Dinosaurs: The Final Day with David Attenborough.”

The documentary was filmed over the course of three years, and as its narrative unfolds Sir David Attenborough will introduce viewers to many of the fossil finds that have been unearthed at Hell Creek Formation since the site was discovered in 2008.

“We’ve got so many details with this site that tell us what happened moment by moment, it’s almost like watching it play out in the movies,” DePalma explained. “You look at the rock column, you look at the fossils there, and it brings you back to that day .”

DePalma and the other paleontologists involved in the research at the Tanis site have yet to submit their latest findings for peer review and publishing. Nevertheless, they chose to reveal what they’d discovered now, to help generate more interest in the upcoming documentary.